Bellringer:

1. Bellringer: • Potassium has two naturally occurring isotopes. potassium—39 has a mass of 38.964 amu and potassium—41 has a mass of 40.962 amu. The atomic mass of potassium is 39.098 amu. What is the % abundance of both isotopes?

2. potassium—39 has a mass of 38.964 amu potassium—41 has a mass of 40.962 amu Atomic mass 39.098 amu Two isotopes abundance must equal 1 or the two isotopes % abundance must equal 100% x+y = 1 therefore y=1-x 39.098amu=38.964amu(x) + 40.962amu(1-x)

3. Radioactivity • One of the pieces of evidence for the fact that atoms are made of smaller particles came from the work of________ (1876-1934). • She discovered________, the spontaneous disintegration of some elements into smaller pieces.

4. Radioactivity • It is not uncommon for some isotopes of an element to be unstable, or radioactive. • We refer to these as radioisotopes. • There are several ways radioisotopes can decay and give off energy known as radiation.

5. Nuclear Reactions vs. Normal Chemical Changes • Nuclear reactions involve the nucleus • The nucleus opens, and protons and neutrons are rearranged • The opening of the nucleus releases a tremendous amount of energy that holds the nucleus together – called binding energy • “Normal” Chemical Reactions involve electrons, not protons and neutrons

6. The Nucleus • Remember that the nucleus is comprised of the two nucleons, protons and neutrons. • The number of protons is the atomic number. • The number of protons and neutrons together is effectively the mass of the atom.

7. Isotopes • Not all atoms of the same element have the same mass due to different numbers of neutrons in those atoms. • There are three naturally occurring isotopes of uranium: • Uranium-234 • Uranium-235* • Uranium-238

8. 238 92 234 90 4 2 4 2 He U Th He +  Types of Radioactive Decay Alpha Decay Loss of an -particle (a helium nucleus)

9. 131 53 131 54 0 −1 0 −1 0 −1 e I Xe e  +  or Types of Radioactive Decay Beta Decay Loss of a -particle (a high energy electron)

10. 0 0  Types of Radioactive Decay Gamma Emission Loss of a -ray (high-energy radiation that almost always accompanies the loss of a nuclear particle)

11. Types of Radiation • Alpha (ά) – a positively charged helium isotope - we usually ignore the charge because it involves electrons, not protons and neutrons • Beta (β) – an electron • Gamma (γ) – pure energy; called a ray rather than a particle

12. Penetrating Ability

13. Nuclear Reactions • Alpha emission Note that mass number goes down by 4 and atomic number goes down by 2. Nucleons (nuclear particles… protons and neutrons) are rearranged but conserved

14. Nuclear Reactions • Beta emission Note that mass number is unchangedandatomic number goes up by 1.

15. Write Nuclear Equations! • Write the nuclear equation for the alpha decay of radon-222 222Rn  218Po + 4He • Write the nuclear equation for the beta emitter Co-60. 60Co  60Ni + 0e 86 84 2 -1 27 28