1. Number of ProtonsAtomic Number Number of NeutronsAtomic Mass – Atomic Number Number of ElectronsNumber of protons (Atomic Number)

3. Chemical Reactivity and Ions

4. Explain a chemical reaction. Explain why there are reactivity differences in families. Explain why the noble gases are generally unreactive. Key Words Octet ruleIonsCationAnion Electrostatic attraction

5. The Octet Rule All electrons found in the outer orbit are called VALENCE electrons. An atom with a FULL outer orbit is very stable. Chemical reactions occur as atoms work together to try to obtain a full outer orbit of valence electrons.

6. Atoms will acquire a full outer shell in 3 ways: Give away an e - to another atom. Take an e - from another atom. Share an e - with another atom. When a neutral atom gives an e - away it ends up with a positive charge. The atom is now called a positive ION OR cation.

7. Sodium atom: 11 p + 11 e - Na Sodium ion: 11 p + 10 e - Na + +

8. Atoms that take an e - end up with a negative charge – called a negative ION (anion) Chlorine atom: 17 p + 17 e - Cl Chlorine ion: 17 p + 18 e - Cl - -

9. Calcium atom: 20 p + 20 e - Ca Calcium ion: 20 p + 18 e - Ca +2 +2

10. Nitrogen atom: 7 p + 7 e - N Nitrogen ion: 7 p + 10 e - N -3 -3

11. Chemical Reactivity is based on the number of electrons gained or lost by an element to have an filled outer orbit. The LESS electrons needed, the GREATER the reactivity of the element. A Chemical Reaction: A movement of electrons between combining atoms that results in the formation of a NEW substance.

12. Electrostatic attraction is the force that brings opposite charges together. Some compounds are formed between ions. + -

13. The Atom - Atoms react or not depending on its electron structure. - All atoms desires to have a full outer electron shell. - Metals will lose e - and nonmetals will gain e -. - Ions combine to form compounds. - Like charges repel, same charges attract. - When elements combine in a chemical reaction to form a new compound ~ all have filled outer electron shells.