IONIC BONDINGAlong with nomenclature of ionic compounds, acids, and molecular

compounds

Terms Formula unit – ionic substances, smallest

whole # ratio Molecular formula – covalent compounds,

actual # of atoms in one molecule Empirical formula – smallest whole #

ratio (ionic formulas are empirical) Hydrates – # water molecules attached

to each molecule Anhydrous – water has been removed Hygroscopic – attracts water Deliquescent – attracts enough water to

dissolve

Ionic Bonds

TRANSFER of electrons Cation + anion Metals lose their valence e- and become

positively charged Nonmetals gain enough e- to have a full

outer shell (octet, or 8) and become negatively charged

Opposites attract! Ionic compounds are formed Electrostatic forces hold ions together

Properties of Ionic Bonding

Hard, brittle, crystalline solids at room temperature

High melting points DO NOT conduct as solids DO conduct when melted or dissolved in

water Most are soluble in water Link

Solutions are electrolytes

Formulas Chemical formula

Shows kinds and numbers of atoms in smallest representative unit NaCl, H2O

Formula unit Ionic compounds form CRYSTALS that vary in

size, because the ions attract from all sides, the ions pack together in an alternating pattern, so the formula shows the lowest whole number ratio of ions

Writing ionic formulas

There are some steps to writing ionic formulas: The cation always goes first The anion goes second The charge of cation becomes the subscript for

the anion The charge of the anion becomes the subscript

for the cation The subscript tells you how many of that

cation/anion is needed to bond to the cation/anion

PracticeK + F Al + O Be + S Al + Br

K + I Mg + I Na + O

Sometimes one loses more e- than the other needs, or vice versa, so the ratio cannot be 1:1

look at the charges, criss-cross them so that they become the subscripts, then reduce if possible; the idea is that the overall charge in a chemical formula is ZERO

Al+3 O-2 Al2O3 Be+2 S-2 Be2S2 BeS

2:2 reduces to 1:1

Mark your Periodic Table!

+1

+2+4

+2

+2+4

All the transition metals except Ag and Zn can have more than one charge and need a Roman numeral (Pb and Sn need one too!)

Metallic Bonding Cations in a sea of electrons

Only occurs in pure metal elements and mixtures

Properties include Malleable, can be flattened into thin sheets Ductile, can be pulled into wire Bendable/shapeable vs brittle ionic

compounds Alloys – metal mixtures, designed for

specific qualities Durability, strength, resistance to corrosion,

lightweight, etc.

Covalent Bonding

sharing of electrons to form molecules Properties of covalent compounds:

lower melting and boiling points than ionic compounds

soft and squishy more flammable than ionic compounds don't conduct electricity in water Are not soluble in water

Coordinate covalent bonding occurs when one element contributes both electrons of the electron pair when the chemical bond forms

Network Solids• Network Covalent: this is a special type

of nonpolar covalent bonding– Rather than forming discrete molecules, the

atoms bond in a continuous, 3-D fashion forming crystalline solids, much like ionic solids– but with some significantly different properties

• Examples: sand (SiO2), diamond (carbon), graphite (carbon)– high melting point– NOT SOLUBLE – NOT CONDUCTIVE

Naming Ionic Compounds

Remember, ionic compounds almost always have a metal

Cations have the same name as the metal (add “ion”)

Anions have the ending changed to –ide, or they are polyatomic and have a special name

Metals that can form more than one type of ion use a Roman numeral equal to the charge to designate the type Fe+2 is iron(II) Fe+3 is iron(III)

Naming Covalent Compounds

Use prefixes to indicate the # of atoms of each element, also use for hydrates (•H2O) Mono, di, tri, tetra, penta, hexa, hepta,

octa, nona, deca; don’t use mono for 1st element

Change ending to –ide NO2 nitrogen dioxide

N2O4 dinitrogen tetroxide (drop the a from the prefix when followed by o)

CuSO4 •5H2O copper(II) sulfate pentahydrate

Organic Compounds

Organic – contains carbon and hydrogenThese have their own special naming

system, using different prefixes for the # of carbons, and suffixes indicating the types of bonds

Naming Organic Compounds

1st indicate # of Carbons 1-meth 2-eth 3-prop 4-but 5-10 same as

inorganic prefixes

Then indicate type of bonds All single bonds

then tack on -ane

CnH2n+2 A double bond add

-ene A triple bond add -

yne Methane, propene,

butyne

Naming Acids

Binary Acids (HCl) “hydro” prefix Root of anion (2nd element) “ic” suffix + acid HCl is hydrochloric acid HF hydrofluoric acid

Naming Acids - polyatomic

MUST recognize the polyatomic ion Change “ite” to “ous” Change “ate” to “ic” + acid H3PO4:

(PO4)- phosphate phosphoric acid All negative polyatomic ions can be acids, just

put hydrogen in front of formula (subscript will be charge of ion)