Names and Formulas of Ionic Compounds

Chemical Bonds O 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 H 2 O

Na +, Cl−, Ca ++, S = H2SO4 O Formula shown is simplest form of the molecule that is formed when ions combine

Ions O Formed when atoms lose or gain valence electrons O May be + or - ions O 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 Radius O What happens to atoms as they lose electrons? Radius decreases O 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 Energy O The energy needed to overcome the attraction between the +positively charged nucleus and the -negatively charged electron O Measured in Joule O Energy required to ionize increases from left to right on pt O Alkali metals –low ionization energies- lose e- readily

O Noble gases have EXTREMELY high IE O rare to lose e- O remain stable O He, Ne, Ar, Kr, Xe, Rn

Octet Rule O Atoms tend to lose or gain e- to finalize a full set of 8 valence electrons O This occurs in ionization O Natural occurrence O Makes compound formation possible

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

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

Where are highest –neg.? O Electronegativity effects properties such as melting and boiling points of substances O Increases from left to right on PT O And decreases from top to bottom

O Subscripts in ionic compounds indicate ratio of cations to anions to form electrically neutral atoms H 2 CO 3

O Monoatomic ions- form from one atom O -1 is the oxidation state or oxidation number Bromide, Br -1 Chloride, Cl -1

Polyatomic ions are formed from 2 or more atoms-act as single unit with net charge Perchlorate, ClO 4 -1 Hydrogen carbonate, bicarbonate, HCO 3 -1 Hydrogen sulfate, HSO 4 -1 Dihydrogen phosphate, H 2 PO 4 -1 Thiocyanate, SCN -1

Naming O Name of cation first followed by name of anion O NaCl Sodium chloride O Mg SO 4 Magnesium sulfate

O Charge 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 O Ba (NO 3 ) 2 Barium is +2 Nitrate is -1.. (need 2 ions)