V. Radioactivity

Recall…Parts of an Atom 3 Parts of the Atom, their location, charge, and mass Electron around the nucleus (electron cloud) negative ~0 amu Proton in the nucleus positive 1 amu Neutron In the nucleus neutral

Recall… Atomic Attributes # of protons # of electrons (in a neutral atom) Mass # Mass of an atom #p+ + #no

Recall… What tells us the identity of the element (atom)? Convert Hydrogen – 3 to nuclear notation

Recall…Isotope Naming Isotope (hyphen) Notation Element Name – mass # Ex: Carbon – 12 or Neon – 22 Nuclear Notation H 3 1

A. Nuclear Reactions Nuclear Reaction = the nucleus of an atom changes and becomes a new ELEMENT.

B. Nuclear Reactions In a nuclear reaction, unstable nucleus changes (LOSES MASS AND ENERGY) to become more stable Unstable if too many or few neutrons

C. Radioactivity Mother of Radioactivity = Marie Curie (1867 – 1934) 2 Nobel Prizes Showed rays emitted by uranium atoms caused fogging in photographic plates Named this process radioactivity Radioactive particles called radiation

C. Radioactivity Radioactivity – the process by which some substances spontaneously emit energy called radiation Radiation – penetrating rays/particles emitted by a radioactive substance Radioactive Decay – An unstable nucleus spontaneously loses energy by emitting radiation

D. Types of Radiation Alpha Radiation Beta Radiation Gamma Radiation

2 4 He (positive charge of 2+) E. Alpha Radiation Alpha (α) particles released α particle = Helium Nucleus (2 protons, 2 neutrons, and 0 electrons) 2 4 He (positive charge of 2+) Produced in large nuclei

−1 0  or −𝟏 𝟎 e (negative charge of 1–) F. Beta Radiation Beta (ß) particles released ß particle = high speed electron leaves nucleus −1 0  or −𝟏 𝟎 e (negative charge of 1–) Occurs in elements with more neutrons than protons: a neutron splits into a proton and electron.

0 0  (zero charge) G. Gamma Radiation Gamma Ray () released  ray = high energy radiation 0 0  (zero charge) Occurs if nucleus is in an excited state and it releases energy (gamma rays). Usually occurs with alpha or beta decay.

Summary – 3 Types of Radiation Radiation Type Symbol Mass (amu) Charge Alpha  2 4 He 4 2+ Beta  −1 0 e ~0 (very small) 1- Gamma  0 0 

H. Radiation Alpha particles = stopped by paper. Beta particles = stopped by wood Most (but not all) Gamma rays = stopped by lead or thick concrete. alpha particles least penetrating, gamma particles most penetrating.