NOTES: Ions

Valence Electrons: ● Knowing electron configurations is important because the number of valence electrons determines the chemical properties of an element. ● Valence Electrons: The e- in the highest occupied energy level of an element’s atoms.

Valence Electrons: ● All elements in a particular group or family have the same number of valence electrons (and this number is equal to the group number of that element) Examples: ● Group 1 elements (Na, K, Li, H): 1 valence e-. ● Group 2 elements (Mg, Ca, Be): 2 valence e-. ● Group 17 (7A) elements (Cl, F, Br): 7 valence e-.

LEWIS STRUCTURES: ● Electron dot structures show the valence electrons as dots around the element’s symbol: ● Li ● B ● Si ● N ● O ● F ● Ne

LEWIS STRUCTURES: ● Electron dot structures show the valence electrons as dots around the element’s symbol: ● Li ● B ● Si ● N ● O ● F ● Ne

Which elements form ionic compounds and which elements form covalent (molecular) compounds?? General Rule of Thumb: metal + nonmetal = IONIC metal + polyatomic anion = IONIC polyatomic cation + anion = IONIC nonmetal + nonmetal(s) = COVALENT

Why are ionic compounds so stable? ● IONIC BONDS: -metal plus a nonmetal -cations plus anions -opposite charges attract ● Examples:  Na + and Cl - form NaCl  Al 3+ and Br - form AlBr 3

Ionic Bonds: Isn’t it ionic that opposites attract?

OCTET RULE: ● Noble gas atoms are very stable; they have stable electron configurations. In forming compounds, atoms make adjustments to achieve the lowest possible (or most stable) energy. ● Octet rule: atoms react by changing the number of electrons so as to acquire the stable electron structure of a noble gas.

Formation of Cations and Anions ● can be predicted using the octet rule (not always followed, but a good general rule to follow for the representative elements) -full outer energy level -eight electrons (s 2 p 6 ) **explains formation of both cations and anions

CATIONS: ● Na: 1s 2 2s 2 2p 6 3s 1 ● Na + : ● Mg: 1s 2 2s 2 2p 6 3s 2 ● Mg 2+ :

CATIONS: ● Na: 1s 2 2s 2 2p 6 3s 1 ● Na + : 1s 2 2s 2 2p 6 ● Mg: 1s 2 2s 2 2p 6 3s 2 ● Mg 2+ : 1s 2 2s 2 2p 6

OCTET RULE: ● Atoms of METALS obey this rule by losing electrons. Na: Na + :

OCTET RULE: ● Atoms of METALS obey this rule by losing electrons. Na: Na + :

ANIONS: ● Cl: 1s 2 2s 2 2p 6 3s 2 3p 5 ● Cl - : ● O:1s 2 2s 2 2p 4 ● O 2- :

ANIONS: ● Cl: 1s 2 2s 2 2p 6 3s 2 3p 5 ● Cl - : 1s 2 2s 2 2p 6 3s 2 3p 6 ● O: 1s 2 2s 2 2p 4 ● O 2- : 1s 2 2s 2 2p 6

OCTET RULE: ● Atoms of NONMETALS obey this rule by gaining electrons. Cl: Cl - :

OCTET RULE: ● Atoms of NONMETALS obey this rule by gaining electrons. Cl: Cl - :

OCTET RULE: ● Transition metals are exceptions to this rule. Example: silver (Ag)  Ag + By losing one electron, it acquires a relatively stable configuration with its 4d sublevel filled (pseudo noble-gas)

OCTET RULE: ● Transition metals are exceptions to this rule. Example: silver (Ag)  Ag + By losing one electron, it acquires a relatively stable configuration with its 4d sublevel filled (pseudo noble-gas)