Key Takeaways Key Points. An atom is composed of two regions: the nucleus, which is in the center of the atom and contains protons and neutrons, and the outer region of the atom, which holds its electrons in orbit around the nucleus.

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1. When is a child’s eligibility for special education and related services determined? In most states the eligibility of a child for special education and related services is considered when a child has arrived at the Tier 3 level of RTI (Response to Intervention).
2. The family group is the first group with which an individual interacts. This group gives the person the essential values that will define his life. It is also in this group that the feeling of belonging for the first time develops. 2- Groups of friends. The group of friends is the second group with which a person establishes relationships.

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On-line version ISSN 1518-8345

http://dx.doi.org/10.1590/S0104-11692008000100013

ORIGINAL ARTICLE

Creation and evaluation cycle of a distance module for nursing undergraduates, named 'Medication admnistration'¹

Paulo Celso Prado Telles Filho^I; Silvia Helena De Bortoli Cassiani^II

^IRN, Doctoral student, Faculty, Federal University of Vales do Jequitinhonha e Mucuri, Brasil, e-mail: ppradotelles@yahoo.com.br
^IIAdvisor, Full Professor, e-mail: shbcassi@eerp.usp.br. University of São Paulo at Ribeirão Preto College of Nursing, WHO Collaborating Centre for Nursing Research Development, Brazil.

ABSTRACT

The objective of this study was to describe the creation cycle of the module 'medication administration' and to evaluate it. It is an evaluation research, using the Engagement Theory as a methodological/theoretical approach carried out in two phases: the first related to the creation of the module and the second to its evaluation by specialists using the instrument based on the Model of Analytical Appreciation of Hypermedia Systems. The creation cycle of the module followed the following steps: gathering the objectives of the module, organization of the content, selection of the media, creation of the classes and activation of the learning process. It was evaluated by contents specialists, informatics specialists and nursing students. The evaluation of the distribution and the accessibility of the contents, the utilization of images, the clarity and ease of execution of the program were positive. The module was considered appropriate to be used with nursing students.

Descriptors: education, distance; nursing; pharmaceutical preparations

INTRODUCTION

The contemporary society demands individuals to develop their abilities of raising theories, reflecting, analyzing and organizing, which validate conscious decision making. It is necessary to develop talents that allow for autonomous ways of creation, communication and expression, generating attitudes of cooperation and reciprocity.

In this perspective, distance education stands out as an educative process in which learning occurs through a physical separation between the students and the teachers. Communication and learning take place through technological resources that go beyond oral exposition.

In this kind of process, both the student who will use it, and the teacher who develops the material need to be capable. Both these parties' motivation for learning is the accelerated scientific and technological development of the current world, which brings about constant changes in work places, demanding professionals able to adapt themselves to the changes and who are equipped and motivated for continuous learning.

A study cited in this research focused on the learning environment, with the use of the Internet, addressing intravenous therapy teaching. It aimed at developing educational material on this therapy, using the Internet and evaluating its use by the students. The latter positively evaluated the learning opportunity through the Internet, mentioning the interaction with the instructor, space-time flexibility, access to technical resources and aspects related to course content organization⁽²⁾.

Therefore, based on the idea that distance education resources are very useful, efforts were made to conduct and use it in the nursing area.

A study that revealed the educational needs of hospital nurses in terms of medication administration exposed the need for knowledge on contents like: action mechanisms, medication preparation and administration, medication interactions, stability, adverse effects of the medication and other aspects⁽³⁾.

This data indicated the existence of knowledge deficits on essential questions for safe and correct medication administration.

In view of these considerations and aware of the challenge of extending knowledge on medication administration, the researcher aimed to carry out a study that would present the contribution related to the subject: teaching medication administration, using distance education as a possibility of development in professional education of nursing undergraduates.

Therefore, the development of this study was proposed, which intended to describe the creation cycle of a distance module called 'Medication Administration', as well as to evaluate it for its later implementation in undergraduate Nursing courses.

OBJECTIVES

This article aimed at:
- Describing the creation cycle of a distance module in the Teleduc environment, called 'Medication Administration'.
- Proceeding to the evaluation of the module mentioned by specialists in content, informatics and undergraduates in nursing, through an instrument based on the Analytical Appreciation Model of Hypermedia Systems.

METHODOLOGY

First Phase

The first phase of the work is an evaluation research, aimed at discovering how well a practice or program is working out when used to search for answers to practical questions⁽⁴⁾.

In nursing education, there is usually a need to evaluate the range of goals and the efficiency of the means used to achieve a goal⁽⁴⁾. This study aimed at describing the development and evaluation of a module in a virtual learning environment, through information and communication technologies available on the web.

The engagement theory developed by Greg Kearsley, a consultant specialized in on-line and distance education, Assistant Professor of the Distance Education Program at the University of Maryland - USA, was used as a theoretical/methodological reference framework.

The option to use the latter is justified because the intention was to develop a distance module for medication administration teaching which would reflect the current and innovative learning focus that unites individuals with common interests and seeks collaboration and connectivity.

The main characteristics of this theory are related to collaboration (students working together); connectivity (all students connected to each other all of the time); community (groups are defined according to common interests) and multi-sensoriality (the information can involve sound, graphs and figures)⁽⁵⁾.

Therefore, its fundamental idea is the interaction among students engaged in learning activities. Such theory differs from others because it promotes human interaction in the context of group activities and not in the individual's interaction with the instructional program only⁽⁶⁾.

Important determinants that stand out in the quality of the instructional material are: little quantity of information on each screen and the use of different styles, font sizes and colors to highlight ideas, using figures to transmit them⁽⁷⁾.

The below figure presents the module development cycle.

Second Phase

Study and Population Location - Target

The module evaluation was developed at a university in the interior of São Paulo, Brazil.

It was carried out by ten specialists: five specialists in content were nurses, post-graduates and university professors. It is worth stressing that all of them attended the criteria of having a Master's Degree and being professors in Nursing Fundamentals. There were five specialists in informatics: a system analyst, an electronic engineer, an undergraduate in Systems Analysis and two informatics technicians. All of them attended the criteria of being involved with informatics and teaching technology, as well as with educational computer programs.

Posters were hung up in the research institution, describing the study goals and asking interested people to contact the researcher. Five students from the eighth term showed up and were interested in participating.

Evaluation Instrument

The evaluation was performed through an instrument based on the Analytical Appreciation Model of Hypermedia Systems⁽⁸⁾, which was adapted and validated⁽⁹⁾ to evaluate educational software.

Ethical Aspects

The study was authorized by the General Board of the research institution. It started after the approval by the Research Ethics Committee at the University of São Paulo College of Nursing, registered under number 0304/2002. Each participant was aware of the Free and Informed Consent Term for Participation in Research and issued a written record with the approval to participate in the research.

RESULTS AND DISCUSSION

First Phase

The steps of the development cycle of the 'Medication Administration' module are described below.

Gathering the objectives of the module

The objectives were raised based on the program content of the subject 'Fundamentals for the Care Process II', taught at the institution where the researcher was a professor; on his experience in courses about the theme, taught to undergraduates and post-graduates in the health area in general and in nursing in particular; on his participation in scientific events where the theme has been discussed with specialists in the area.

The objectives of the module are presented as follows.

- General Objective

Develop competences related to several contents about medication administration and to the execution of its techniques, to motivate students for the development.

- Specific Objective

Class 1: develop competences related to pharmacological aspects, nursing orientations and information sources for safe medication administration.

Class 2: develop competences related to the preparation of the material for medication administration.

Class 3: develop competences related to intradermal medication administration.

Class 4: develop competences related to subcutaneous medication administration.

Class 5: develop competences related to intramuscular medication administration.

Class 6: develop competences related to endovenous medications administration.

Content organization

After the module objectives were determined, the content was organized. Therefore, all material was joined to be organized in a logical sequence for its broad and clear presentation.

Scientific articles, several materials prepared as content for the classes, materials presented in scientific events and books were part of this material. The content was organized as presented in Table 1.

A fact that stands out is that each class mentioned above has specific exercises and that the entire content in this table was compiled into a text, presented in 102 pages, typed and reviewed using the text editor Word.

It also stands out that this content went through a language adaptation process, in order to become appropriate for the interactive communication means of the Internet. For this purpose, some points were observed, such as the recommendation that the style should be simple and used in the habitual sense, that the images should be subtitled, the paragraphs should be short and that competent sources of quotation and reference should be used, as well as the fact that hyperlinks at the end of each screen should be stimulated and the quantity of text should be reduced, but not of information⁽¹⁰⁾.

Media selection

After determining the objectives and organizing the content, the media selection proceeded, which is a crucial moment for the professor, because it is the time to decide on the best way to present the content to the students⁽¹¹⁾.

After the long bibliographic material reading, the discussion with postgraduate colleagues, pedagogues and systems analysts, the whole content was made available in the Teleduc environment.

Teleduc was considered a support environment for the distance education on the web that has been developed since 1997 by the Center of Informatics Applied to Education - NIED, in partnership with the Institute for Computer Sciences Institute - IC, both from the State University of Campinas (UNICAMP). This environment was developed in a continuous and participative way, having all of its tools idealized and projected according to the needs related by its users⁽¹²⁾.

The architecture of this platform was developed based on the activities. Several tools were arranged for the student, such as support and reading material and frequent questions. These tools promote both teacher-student and student-student interaction and, consequently, collective work.

Creation of classes

The creation of classes followed the determination of the module objectives, as well as the content organization and media selection, which were already presented.

A fact that stands out is that 120 photographs were taken, especially produced for the module. After the association of the objectives, contents and possibilities established for the media, the classes were creation as shown in the following conceptual maps.

It is important to stress that the classes related to subcutaneous, intramuscular and endovenous medication administration followed conceptual mappings similar to the class on intradermal administration.

Activation of the learning process

The module has a total schedule of 50 hours, considering the hours of meetings at school (13 hours and 20 minutes), classes in the Teleduc environment (20 hours), as well as classes in the laboratory (16 hours and 40 minutes).

The four meetings aim to provide information on specific needs during the module implementation. This way, in the first meeting, students are offered general orientations about the module development, explaining and demonstrating its use, which approximates the students, the instructor and the on-line Teleduc environment. The second and third meetings are held after the conclusion of classes 3 and 6, because it is believed that, in this period, content revisions are necessary, in which possible questions related to the corresponding contents are answered. In the fourth meeting, the theoretical evaluation is made.

What the distance content is concerned, there is the screen 'Welcome', presenting the necessary information to learn how to use the Teleduc platform, essential for the process. In order to continue the user experience, it is necessary that the participant uses the tool 'course dynamic', through which the students get information on class dates and schedules, contents, exercises, chats, forums, laboratory classes and evaluations scheduled during the module.

It is important to highlight that the dynamic of the module comprises the following sequence of activities: classes, exercises, chats and forum discussions. On these screens, the dates scheduled for this sequence are specified; it is important to stress that the classes are available during the entire period of the module development and that the exercises, chats and forums discussions are available for a week from the publication of the content of the classes it refers to.

In order to access the content of the class itself, the tool 'readings' should be used.

The opening screen of the classes of the module allows the students to surf in a non linear way, in other words, according to their study needs. The student can access the content from classes one to six, the support material, the image links and list of references.

After studying the content regarding the class, the exercises are done and the program provides the student a grade immediately after its conclusion.

The next steps are the use of the chat session and the discussion forum, which the students use to exchange information on the content studied, as well as to clarify questions; the professor can then visualize the students' access and register them for later analysis.

The laboratories, from one to five, refer to practical classes, in other words, to technique training and practical evaluation. Laboratory 1 deals with the preparation of the material for injectable intradermal medication; laboratory 2, subcutaneous; laboratory 3, intramuscular; laboratory 4, endovenous and laboratory 5, practical evaluation.

In order to follow-up the students' development, formative evaluation is used, verifying and quantifying, in short periods of time and with tools from Teleduc, the accesses to the following items: content of each class, exercise access and resolution, access to the chat and discussion forum.

The additive evaluation takes place at the end of the module, through two classroom evaluations: a theoretical and a practical one, both using printed material, according to the guidelines of the educational institution where the module is implemented.

Second Phase

The results of evaluations by specialists in content refer to the content distribution and accessibility, the explicitness of its presentation, the structure and accuracy of the information presented, the utilization of images and its relation to the text information, the presentation of diverse texts that correspond to the objectives of the module and the relevance of the exercises to reinforce the content.

The unanimous agreement of the specialists in content regarding all items above cited and evaluated was observed, as all of the five participants checked the item 'In Conformity' of the instrument used.

Positive aspects emerged from these observations, mostly in what concerns the photographs in a process of detriment of images; the placement of tests at the end of each class; the existence of personal meetings during the module, as a way to clarify possible questions; the information quality and its contribution to daily nursing practice; content explicitness and quantity, the tests put at the end of each class as a possibility of revision and fixation of the knowledge acquired and the instructional sequence of the classes as learning motivators.

Continuing with the evaluation by specialists, there is the evaluation by the specialists in informatics.

The items evaluated by these specialists were reported regarding their explicitness and the visualization of the main menu presentation, logical and pleasant sequence of the classes, suitability of the visual presentation for the study objective, easy execution of the program, speed of access, accessibility of the contents, efficient use of platform resources and easy interaction and communication provided by the environment. Regarding the items mentioned, 100% of conformity was registered.

As to the observations, information regarding the quality of the education system and easy accessibility were described. However, an item was pointed out as requiring modification regarding the item readings, as the quantity of bibliographical references should be increased.

After the modification was carried out, there was the evaluation by undergraduates from a nursing course, described next.

The same items evaluated by the specialists in informatics and content were evaluated by five undergraduates and, according to the records, 12 items received the classification 'In Conformity'. Three participants disagreed with the items 'The main menu presentation is clear and of easy visualization' and 'The access is fast'.

Some positive aspects emerged in the observations, such as the relation of the module to the digital evolution and professional development, the placement of the content in a clear way and the use of the module for students and people outside the health area.

Regarding aspects requiring modification, the delay in access time stood out. It should be explained that this depends on the net the student is accessing the program from, as each network has a different configuration that interferes with the speed.

After all modifications were completed, it is believed that the module is appropriate to be implemented in undergraduate nursing courses.

FINAL CONSIDERATIONS

This study described the creation cycle of the 'Medication Administration' module, developed in the educational environment Teleduc, based on up-to-date bibliography. For this purpose, Engagement Theory was used, which seeks the union of individuals with common interests, collaboration and connectivity.

The following sequence was adopted for the description: determining the objectives of the module, content organization, media selection, creation of classes and activation of the learning process.

The 'Medication Administration' module was created in the Teleduc environment, based on up-to-date bibliography and with practical examples. It is a resource integrated to the pedagogical process as one of its mediators, providing the participants with knowledge construction on medication administration, to be built in constant interaction between students and teacher.

It was positively evaluated by specialists in content, informatics and undergraduates in nursing in terms of content distribution and accessibility, explicitness of its presentation, information structure and accuracy, image utilization and its relation to the text information, presentation of diverse texts, relevance of the exercises for content reinforcement, explicitness and visualization of main menu presentation, logical and pleasant sequence of the classes, suitability of visual presentation, easy execution of the program and interaction and communication provided by the environment. The module was then considered appropriate for use with nursing undergraduates.

REFERENCES

1. Magdalena BC, Costa IT. Internet na sala de aula: com a palavra os professores. Porto Alegre: Artmed; 2003. [ Links ]

2. Dias D.C, Cassiani SHB. Educação sem distâncias: utilização do Web CT como ferramenta de apoio para o ensino de terapia intravenosa na graduação de enfermagem. Rev Brasileira de Enfermagem 2003; 56(4):443-6. [ Links ]

3. Telles PCP Filho, Cassiani SHB. Administração de medicamentos: aquisição de conhecimentos e habilidades requeridas por um grupo de enfermeiros. Rev Latino-Americana de Enfermagem 2004; 12(3):533-40. [ Links ]

4. Polit D, Hungler BP. Nursing research - principles and methods. 6ª ed. Philadelphia: Lippicontt; 1999. [ Links ]

Essential Question 9:changemr. Mac's Virtual Existence Key

5. Kearsley G. New Developments in Learning. [citado em 2004 jul 7]. Disponível em: http://home.sprynet.com/~gkearsley/.htm. [ Links ]

6. Kearsley G. O profesor virtual: um estudo de caso pessoal. [citado em 2003 dez 23] Disponível em: http://home.sprynet.com/~gkearsley/.htm. [ Links ]

7. Kearsley G. Training for tomorrow. Distributed learning through computer and communications technology. New York: Addison-Wesley Publishing; 1985. [ Links ]

8. Struchiner M. Introdução a informática na área da saúde. Rio de Janeiro: NUTES/UFRJ; 1997 [ Links ]

9. Lopes MVO, Araújo TL, Silva RM. Software para o auxílio a prática docente no ensino de necessidades humanas básicas. Texto & Contexto - Enfermagem. 2000; 9(1):79-92. [ Links ]

10. Kearsley G, Moore M. Distance education: a system view. Belmont (USA): Wasdsworth Publishing; 1996. [ Links ]

11. Zaína LAM. Acompanhamento do aprendizado do aluno em curso a distância através da Web: metodologias e ferramentas [dissertação]. São Paulo (SP): Escola Politécnica/USP; 2002. [ Links ]

12. Rocha HV. O ambiente Teleduc para educação a distância baseada na Web: princípios, funcionalidades e perspectivas de desenvolvimento. Campinas (SP): Unicamp; 2000. [ Links ]

Recebido em: 23.5.2006
Aprovado em: 12.9.2007

1 Paper extracted from Doctoral Dissertation

Overview of Atomic Structure

Atoms are made up of particles called protons, neutrons, and electrons, which are responsible for the mass and charge of atoms.

Learning Objectives

Discuss the electronic and structural properties of an atom

Key Takeaways

Key Points

• An atom is composed of two regions: the nucleus, which is in the center of the atom and contains protons and neutrons, and the outer region of the atom, which holds its electrons in orbit around the nucleus.
• Protons and neutrons have approximately the same mass, about 1.67 × 10-24 grams, which scientists define as one atomic mass unit (amu) or one Dalton.
• Each electron has a negative charge (-1) equal to the positive charge of a proton (+1).
• Neutrons are uncharged particles found within the nucleus.

Key Terms

• atom: The smallest possible amount of matter which still retains its identity as a chemical element, consisting of a nucleus surrounded by electrons.
• proton: Positively charged subatomic particle forming part of the nucleus of an atom and determining the atomic number of an element. It weighs 1 amu.
• neutron: A subatomic particle forming part of the nucleus of an atom. It has no charge. It is equal in mass to a proton or it weighs 1 amu.

An atom is the smallest unit of matter that retains all of the chemical properties of an element. Atoms combine to form molecules, which then interact to form solids, gases, or liquids. For example, water is composed of hydrogen and oxygen atoms that have combined to form water molecules. Many biological processes are devoted to breaking down molecules into their component atoms so they can be reassembled into a more useful molecule.

Atomic Particles

Atoms consist of three basic particles: protons, electrons, and neutrons. The nucleus (center) of the atom contains the protons (positively charged) and the neutrons (no charge). The outermost regions of the atom are called electron shells and contain the electrons (negatively charged). Atoms have different properties based on the arrangement and number of their basic particles.

The hydrogen atom (H) contains only one proton, one electron, and no neutrons. This can be determined using the atomic number and the mass number of the element (see the concept on atomic numbers and mass numbers).

Structure of an atom: Elements, such as helium, depicted here, are made up of atoms. Atoms are made up of protons and neutrons located within the nucleus, with electrons in orbitals surrounding the nucleus.

Atomic Mass

Essential Question 9:changemr. Mac's Virtual Existence -

Protons and neutrons have approximately the same mass, about 1.67 × 10^-24 grams. Scientists define this amount of mass as one atomic mass unit (amu) or one Dalton. Although similar in mass, protons are positively charged, while neutrons have no charge. Therefore, the number of neutrons in an atom contributes significantly to its mass, but not to its charge.

Electrons are much smaller in mass than protons, weighing only 9.11 × 10^-28 grams, or about 1/1800 of an atomic mass unit. Therefore, they do not contribute much to an element’s overall atomic mass. When considering atomic mass, it is customary to ignore the mass of any electrons and calculate the atom’s mass based on the number of protons and neutrons alone.

Electrons contribute greatly to the atom’s charge, as each electron has a negative charge equal to the positive charge of a proton. Scientists define these charges as “+1” and “-1. ” In an uncharged, neutral atom, the number of electrons orbiting the nucleus is equal to the number of protons inside the nucleus. In these atoms, the positive and negative charges cancel each other out, leading to an atom with no net charge.

Protons, neutrons, and electrons: Both protons and neutrons have a mass of 1 amu and are found in the nucleus. However, protons have a charge of +1, and neutrons are uncharged. Electrons have a mass of approximately 0 amu, orbit the nucleus, and have a charge of -1.

Exploring Electron Properties: Compare the behavior of electrons to that of other charged particles to discover properties of electrons such as charge and mass.

Essential Question 9:changemr. Mac's Virtual Existence Reality

Volume of Atoms

Accounting for the sizes of protons, neutrons, and electrons, most of the volume of an atom—greater than 99 percent—is, in fact, empty space. Despite all this empty space, solid objects do not just pass through one another. The electrons that surround all atoms are negatively charged and cause atoms to repel one another, preventing atoms from occupying the same space. These intermolecular forces prevent you from falling through an object like your chair.

Interactive: Build an Atom: Build an atom out of protons, neutrons, and electrons, and see how the element, charge, and mass change. Then play a game to test your ideas!

Atomic Number and Mass Number

The atomic number is the number of protons in an element, while the mass number is the number of protons plus the number of neutrons.

Learning Objectives

Determine the relationship between the mass number of an atom, its atomic number, its atomic mass, and its number of subatomic particles

Key Takeaways

Key Points

• Neutral atoms of each element contain an equal number of protons and electrons.
• The number of protons determines an element’s atomic number and is used to distinguish one element from another.
• The number of neutrons is variable, resulting in isotopes, which are different forms of the same atom that vary only in the number of neutrons they possess.
• Together, the number of protons and the number of neutrons determine an element’s mass number.
• Since an element’s isotopes have slightly different mass numbers, the atomic mass is calculated by obtaining the mean of the mass numbers for its isotopes.

Key Terms

• mass number: The sum of the number of protons and the number of neutrons in an atom.
• atomic number: The number of protons in an atom.
• atomic mass: The average mass of an atom, taking into account all its naturally occurring isotopes.

Atomic Number

Neutral atoms of an element contain an equal number of protons and electrons. The number of protons determines an element’s atomic number (Z) and distinguishes one element from another. For example, carbon’s atomic number (Z) is 6 because it has 6 protons. The number of neutrons can vary to produce isotopes, which are atoms of the same element that have different numbers of neutrons. The number of electrons can also be different in atoms of the same element, thus producing ions (charged atoms). For instance, iron, Fe, can exist in its neutral state, or in the +2 and +3 ionic states.

Mass Number

An element’s mass number (A) is the sum of the number of protons and the number of neutrons. The small contribution of mass from electrons is disregarded in calculating the mass number. This approximation of mass can be used to easily calculate how many neutrons an element has by simply subtracting the number of protons from the mass number. Protons and neutrons both weigh about one atomic mass unit or amu. Isotopes of the same element will have the same atomic number but different mass numbers.

Atomic number, chemical symbol, and mass number: Carbon has an atomic number of six, and two stable isotopes with mass numbers of twelve and thirteen, respectively. Its average atomic mass is 12.11.

Scientists determine the atomic mass by calculating the mean of the mass numbers for its naturally-occurring isotopes. Often, the resulting number contains a decimal. For example, the atomic mass of chlorine (Cl) is 35.45 amu because chlorine is composed of several isotopes, some (the majority) with an atomic mass of 35 amu (17 protons and 18 neutrons) and some with an atomic mass of 37 amu (17 protons and 20 neutrons).

Given an atomic number (Z) and mass number (A), you can find the number of protons, neutrons, and electrons in a neutral atom. For example, a lithium atom (Z=3, A=7 amu) contains three protons (found from Z), three electrons (as the number of protons is equal to the number of electrons in an atom), and four neutrons (7 – 3 = 4).

Isotopes

Isotopes are various forms of an element that have the same number of protons, but a different number of neutrons.

Learning Objectives

Discuss the properties of isotopes and their use in radiometric dating

Key Takeaways

Key Points

• Isotopes are atoms of the same element that contain an identical number of protons, but a different number of neutrons.
• Despite having different numbers of neutrons, isotopes of the same element have very similar physical properties.
• Some isotopes are unstable and will undergo radioactive decay to become other elements.
• The predictable half-life of different decaying isotopes allows scientists to date material based on its isotopic composition, such as with Carbon-14 dating.

Key Terms

• isotope: Any of two or more forms of an element where the atoms have the same number of protons, but a different number of neutrons within their nuclei.
• half-life: The time it takes for half of the original concentration of an isotope to decay back to its more stable form.
• radioactive isotopes: an atom with an unstable nucleus, characterized by excess energy available that undergoes radioactive decay and creates most commonly gamma rays, alpha or beta particles.
• radiocarbon dating: Determining the age of an object by comparing the ratio of the 14C concentration found in it to the amount of 14C in the atmosphere.

What is an Isotope?

Isotopes are various forms of an element that have the same number of protons but a different number of neutrons. Some elements, such as carbon, potassium, and uranium, have multiple naturally-occurring isotopes. Isotopes are defined first by their element and then by the sum of the protons and neutrons present.

• Carbon-12 (or ¹²C) contains six protons, six neutrons, and six electrons; therefore, it has a mass number of 12 amu (six protons and six neutrons).
• Carbon-14 (or ¹⁴C) contains six protons, eight neutrons, and six electrons; its atomic mass is 14 amu (six protons and eight neutrons).

While the mass of individual isotopes is different, their physical and chemical properties remain mostly unchanged.

Isotopes do differ in their stability. Carbon-12 (¹²C) is the most abundant of the carbon isotopes, accounting for 98.89% of carbon on Earth. Carbon-14 (¹⁴C) is unstable and only occurs in trace amounts. Unstable isotopes most commonly emit alpha particles (He²⁺) and electrons. Neutrons, protons, and positrons can also be emitted and electrons can be captured to attain a more stable atomic configuration (lower level of potential energy ) through a process called radioactive decay. The new atoms created may be in a high energy state and emit gamma rays which lowers the energy but alone does not change the atom into another isotope. These atoms are called radioactive isotopes or radioisotopes.

Radiocarbon Dating

Carbon is normally present in the atmosphere in the form of gaseous compounds like carbon dioxide and methane. Carbon-14 (¹⁴C) is a naturally-occurring radioisotope that is created from atmospheric ¹⁴N (nitrogen) by the addition of a neutron and the loss of a proton, which is caused by cosmic rays. This is a continuous process so more ¹⁴C is always being created in the atmosphere. Once produced, the ¹⁴C often combines with the oxygen in the atmosphere to form carbon dioxide. Carbon dioxide produced in this way diffuses in the atmosphere, is dissolved in the ocean, and is incorporated by plants via photosynthesis. Animals eat the plants and, ultimately, the radiocarbon is distributed throughout the biosphere.

In living organisms, the relative amount of ¹⁴C in their body is approximately equal to the concentration of ¹⁴C in the atmosphere. When an organism dies, it is no longer ingesting ¹⁴C, so the ratio between ¹⁴C and ¹²C will decline as ¹⁴C gradually decays back to ¹⁴N. This slow process, which is called beta decay, releases energy through the emission of electrons from the nucleus or positrons.

After approximately 5,730 years, half of the starting concentration of ¹⁴C will have been converted back to ¹⁴N. This is referred to as its half-life, or the time it takes for half of the original concentration of an isotope to decay back to its more stable form. Because the half-life of ¹⁴C is long, it is used to date formerly-living objects such as old bones or wood. Comparing the ratio of the ¹⁴C concentration found in an object to the amount of ¹⁴C in the atmosphere, the amount of the isotope that has not yet decayed can be determined. On the basis of this amount, the age of the material can be accurately calculated, as long as the material is believed to be less than 50,000 years old. This technique is called radiocarbon dating, or carbon dating for short.

Application of carbon dating: The age of carbon-containing remains less than 50,000 years old, such as this pygmy mammoth, can be determined using carbon dating.

Other elements have isotopes with different half lives. For example, ⁴⁰K (potassium-40) has a half-life of 1.25 billion years, and ²³⁵U (uranium-235) has a half-life of about 700 million years. Scientists often use these other radioactive elements to date objects that are older than 50,000 years (the limit of carbon dating). Through the use of radiometric dating, scientists can study the age of fossils or other remains of extinct organisms.