Names and Formulasof

Ionic Compounds

Chemical BondsO The bond is the force that holds two

or more atoms together to form a molecule of a compound- two types

O Ionic and covalent

O Atom is to element as H He Fe Na

O Molecule is to compound H2O

Na +  , Cl−, Ca ++  , S = 

H2SO4 

O Formula shown is simplest form of the molecule that is formed

when ions combine

IonsO Formed when atoms lose or gain

valence electronsO May be + or - ionsO They form a stable electron

configuration of 8 outer electrons like the noble gases

O Cation is + charged ion; loses e-O Anion is – charged ion; gains e-

O Ionic bonds form when anion and cations close to each other attract and form a geometric lattice

O Force of attraction must be broken to free atoms from each other- usually energy

O Physical properties of ionic solids (NaCl salt) like m.p., b.p. hardness, ability to conduct electricity(melted or in solution) attest to strength of bond

O Electrolyte: conducts electric current in liquid solution

Atomic RadiusO What happens to atoms as they lose

electrons? Radius decreasesO Opposite? Radius increases

O What trends of atomic radius would one expect as atomic number increases?

O As one moves from metals to non –metals?

O As one moves up and down the table?

Ionization EnergyO The energy needed to overcome the

attraction between the +positively charged nucleus and the -negatively charged electron

O Measured in JouleO Energy required to ionize increases

from left to right on pt O Alkali metals –low ionization

energies- lose e- readily

ONoble gases have EXTREMELY high IE

O rare to lose e- Oremain stable

OHe, Ne, Ar, Kr, Xe, Rn

Octet RuleO Atoms tend to lose or gain e- to

finalize a full set of 8 valence electrons

O This occurs in ionizationO Natural occurrenceO Makes compound formation possible

PT right side, gain e- - ions or anionsPT left side, lose e- +ions or cations

ElectronegativityOElectronegativity is a number that describes the relative ability of an atom, when bonded, to attract electrons.

Where are highest –neg.?

OElectronegativity effects properties such as melting and boiling points of substances

OIncreases from left to right on PT

OAnd decreases from top to bottom

OSubscripts in ionic compounds indicate ratio of cations to anions to form electrically neutral atoms

H2CO3

OMonoatomic ions- form from one

atomO -1 is the oxidation state or oxidation

numberBromide, Br-

1

Chloride, Cl-1

Polyatomic ions are formed from 2 or more atoms-act as single unit with net charge

Perchlorate, ClO4-1

Hydrogen carbonate, bicarbonate, HCO3

-1

Hydrogen sulfate, HSO4-1

Dihydrogen phosphate, H2PO4

-1

Thiocyanate, SCN-1

NamingO Name of cation first followed by

name of anion

O NaCl Sodium chlorideO Mg SO4

Magnesium sulfate

OCharge on cation and anion must = zero for an ionic compound to form

O If charge is -1 it can only form bond with other ion +1

O If charge is -2, can form compound with +2 or two ions of +1

Barium Nitrate

OBa (NO3)2 Barium is +2 Nitrate is -1.. (need 2 ions)