4.4 Unstable Nuclei and Radioactive Decay

4.4 Unstable Nuclei and Radioactive Decay

Section 4.4 Unstable Nuclei and Radioactive Decay Objectives Explain the relationship between unstable nuclei and radioactive decay. Characterize alpha, beta, and gamma radiation in terms of mass and charge.

Radioactivity Chemical Reactions Atoms of one element do not change into atoms of another element during a chemical reaction. Why? Radioactivity Chemical reactions involve the rearrangement of atoms not their destruction.

Chemical reactions involve only an atoms electrons the nucleus remains unchanged. Radioactivity Nuclear Reactions These are reactions that involve an atom of one element changing into an atom of another element. These reactions involve the change of an atoms nucleus.

Radioactivity In the late 1890s, radioactivity was discovered. Radioactivity is a process in which some substances spontaneously emit radiation. Radiation is the name for the energy (rays) and particles emitted by radioactive material. Scientists discovered that by emitting radiation, atoms of one element could change into atoms of another element.

Radioactivity Why does radioactivity occur? Radioactive atoms emit radiation because their nuclei are unstable*. Unstable systems gain stability by losing energy. Unstable nuclei lose energy by emitting radiation in a spontaneous process called radioactive decay.

Radioactive decay continues until stable, non-radioactive atoms form. They are often of a different element. Types of Radiation Research, begun in the late 1880s, used electrically charged plates. Scientists were able to identify 3 types of radiation. Types of Radiation

Alpha Radiation Deflected to negatively charged plates. Made up of alpha particles: 2 protons and 2 neutrons with a +2 charge. Symbol for an alpha particle is 42 or 42He (the helium nucleus) Example of alpha decay

Alpha Radiation Note what happens to the atomic number of an element upon emission of an alpha particle. The atom giving up the alpha particle has its atomic number reduced by two. This results in the atom becoming a different element. In the example, Radium-226 undergoes alpha decay to form Radon-222.

Alpha Radiation 226 88 Ra --> 22286Rn + 4 2

He This type of equation is known as a nuclear equation. The atomic numbers and mass numbers of all particles involved are shown. Note that both atomic number and mass number are conserved in a nuclear equation.

Practice Problems Complete the following nuclear equations for alpha decay: 1 24195Am ----> 2 _____ ----> 42He + 23592U 3 235 92

U ----> 4 _____ ----> 42He + 20684Po Types of Radiation Beta radiation Deflected towards the positively charged plate Consists of fast-moving electrons called beta particles.

They have a 1- charge. Symbol for a beta particle is 0-1 or 0-1e. Example of beta decay Beta Radiation The atom giving up the beta particle has its atomic number increased by one. This results in the atom becoming a different element. In the example, carbon-14 undergoes beta decay to

form nitrogen-14, according to the equation: 14 C ---> 0 e + 14 N. 6 -1 7 Note that, in the equation, atomic numbers and mass numbers are conserved. Beta Radiation Since beta radiation is a type of nuclear radiation, the

beta particle is emitted by the nucleus of an atom. How, you may ask, is it possible for an electron to come from a nucleus?? Scientists believe that neutrons are actually composed of 2 particles - an electron and a proton. In beta decay, the electron is emitted and the proton is left, increasing the atomic number. Practice Problems Complete the following nuclear equations for

beta decay. 1. 6027Co ----> 2. _____ ---> 0-1e + 23191Pa 3. 9740Zr ---> 4. _____ ---> 0-1e + 6630Zn Types of Radiation Gamma Radiation Also called gamma rays It is high-energy electromagnetic radiation. It has no charge. It also has no mass so its emission

does not change the element. However, gamma radiation often accompanies alpha and beta emission, which do change the element's identity. Symbol for a gamma ray is 00 or just Gamma rays account for most of the energy lost during the radioactive decay process. Types of Radiation Unstable* Nuclei Why are some atoms unstable?

The primary factor in determining stability is the ratio of neutrons to protons. Atoms containing either too many or too few neutrons are unstable. Unstable nuclei lose enough energy and emit enough particles during radioactive decay to eventually form a nucleus with a stable neutron to proton ratio.

Recently Viewed Presentations

  • Lecture #5 - Anatomical Structure of Softwoods, part I

    Lecture #5 - Anatomical Structure of Softwoods, part I

    Lecture #5 - Anatomical Structure of Softwoods, part I ... Strand Tracheids (STs) Strand tracheids are short cells that are arranged in longitudinal strings or "strands" STs have one or two "square ends" They contain bordered pits. They are usually...
  • Refining Your Research Question In this session, we

    Refining Your Research Question In this session, we

    Refining Your Research Question In this session, we will… Discuss guidelines for creating a 'good' research question Provide time to revisit and revise your research questions and plans Consider appropriate methods for investigating your research question(s) Guiding Principles for Scientific...
  • BEHOLD THE GOD-MAN Part One - Deity Look,

    BEHOLD THE GOD-MAN Part One - Deity Look,

    "Look, I am coming soon, and my reward is with me to repay each person according to his work.I am the Alpha and the Omega, the first and the last, the beginning and the end.. Revelation 22:12-13. CSB "In the...
  • Chapter 10 Liquids, Solids and Phase Changes The

    Chapter 10 Liquids, Solids and Phase Changes The

    What is the experimental evidence for these forces? Electronegativities a dipole is a vector, that is it has both magnitude and direction Dipole moment is define as charge separation*distance of separation; dipole moments are vectors is so far as they...
  • Inspiration for a New Nation

    Inspiration for a New Nation

    Discuss the main ideas of self government and consent of the governed (make connection to John Locke). Review what it would be like to live in a state without any government and discuss the need for government to maintain order...
  • Higher Close Reading - Mrs Ruxton

    Higher Close Reading - Mrs Ruxton

    Higher Close Reading Close Reading skills can be improved by practice; however there is something that many pupils do not realise: there are techniques that you can learn! Your NABs and exam ask similar types of questions and recognising those...
  • DRAMATHERAPY IN SRI LANKA RAVINDRA RANASINHA Teacher in

    DRAMATHERAPY IN SRI LANKA RAVINDRA RANASINHA Teacher in

    Renée Emunah (Director -Dramatherapy Programme, California Institute of Integral Studies) BUDDHISTIC RELIGIOSITY PIRITH BO TREE FOLK BELIEFS EVIL EYE AND EVIL MOUTH DREAMS ANIMALS, SNAKES AND BIRDS MYTHIC PERFORMANCE GODS DEMONS SPIRITS SYMBOLS Purification with the help of water, blood,...
  • Statistical Methods for Biotechnology Products

    Statistical Methods for Biotechnology Products

    Statistical Methods for Biotechnology Products Accelerated Testing by Jen-pei Liu, PhD, Professor Division of Biometry, Department of Agronomy ... to verify that the stability of the drug product will be maintained within specifications for animal studies such as lexicological trials.