Warm Up 10-1-15 1.Where are the biggest atoms on the periodic table? 2.Arrange the following elements in increasing electronegativity: Cl, As, Sn 3.Which.

Warm Up 10-1-151. Where are the biggest atoms

on the periodic table?2. Arrange the following elements

in increasing electronegativity: Cl, As, Sn3. Which trend(s) describe this graph

Agenda-Turn in WS quiz review-Quiz Unit 3-Notes unit 3-4-WS Nuclear Decay

HomeworkOct 9 - Test Unit 3Oct 9 - Midterm Exam (45 Qs)Oct 9 - Online HW Unit 3

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Quiz Unit 3• You may write on the quiz• Unit 3-1 through 3-3• 6 free response questions

Unit 3-4Nuclear Chemistry

Nuclear ReactionsChemical Reactions: Atoms rearrange to form new substances, but atoms’ identities do not change. (electrons change, but nucleus remains the same) Nuclear Reactions: Chemical RxN that involves the changing of an atom’s nucleus. Large amounts of energy released compared to chemical reactions (mass defect)

Nuclear Force• The nucleus is held together by residual strong

force

• Much stronger than the electrical repulsion between the protons

• Stable nucleus have a ratio of 1 to 1.5 for neutrons to protons

quarks & gluonstransfer in the nucleus

Radioisotopes• Radioisotopes- unstable isotopes that

gain stability by releasing radioactive particles. α (alpha), β (beta), and γ (gamma)

Unstable isotope stable

alpha

betagamma

Half-Life• Half-life is the time required for half of a

radioactive substance to decay (to be stable).

-20 g sample has a half-life of 5 years. How much is left after 10 years?

5 g-How much is left after 3 half-lives?

2.5 g-After 4 half-lives how many percent is still radioactive?

6.25%

• N-13 emits beta radiation with a half-life of 10 min. How long is three half lives?– 30 min

• How many grams of the isotope will be left if there were 10 g of N-13?– 1.25 g

Assignments

• Summary• Question #16 ONLY on the worksheet today• Current event news article