Properties of Ionic and Covalent Compounds .

Expanded Octet

An element in the 3rd period or below may have more than eight electrons around them -lewis structure with LESS formal charges are always better representing thst those having more charges

NH3

ammonia

Ionic compound

Name the cation followed by the name of the anion.

C6H12O6

glucose

Naming and Writing Formulas of Compound

-Ionic compound: ions must combine at specific ration based on their charge, so the number of each ion does NOT need to be indicated in the name. -covalent compound: atoms of the same elements can combine in different ratios, so the number of atoms of each elemnts needs to indicated in the name

Polar covalent

-Their EN values are significatly different but not enough to cause full transefer -The atom with the higher EN pulls the bonding electron more. -Partial charges develope on the atom.

Molecular(covalent) compounds

-can be gases, liquids, or solids) -lower melting and boiling point -don't conduct electricity -made up of molecules that have no charge -covalent bonds are present: electrons are shared between atoms

Valence electron

-electrons in the outermost shell of an atom -involve in bonding -for representative(main) elements and noble gases only s and p subshells.

Covalent Bonding

-form between atoms with similar tendencies to gain or lose electrons -compouds containing covalent bonds are called covalent or molecular compunds and are composed of molecules. -A truly covalent bond can only occur when both atoms are identical.

Naming Covalent Compoud

-the name of the elements are written in the order in which they appear in the formula, with the least EN element written first. -a prefix inndicates the number of each kind of atom.

Ionic compounds

-typically solid -high melting and boiling points -good conductors of electricity -made of ions, which are charged particles -Ionic bonds are present.: electrons are tranferred between atoms

Common Noneclature System

-use -ic to inidicate the higher of the charges that ion might have. -use -ous to indicate the lower of the charges that ions might have Examples: -FeCL2 is ferrous chloride -FeCl3 is ferric chloride -Cu2O is cuprous oxide -CuO is cupric oxide

Binary compound

A binary compund is one in which only two elements are present Binary ionic compounds contain a metal and a non metal -The cation and anion arrange themselves in a regular three-dimensional repeating array called CRYSTAL LATTICE Binary molecular compound contain two non-metals -no ions are present

Compound

A compound is a molecule that contains at least two different elements.

Coordinate Covalent bonds

A covalent bond im which BOTH electrons of a shared pair comes from ONE of the atoms.

Electronegativity

A measure of the ability of an atom to attract electrons in a chemical bond. -The difference in EN determines the extent of the bonds polarity

Formal charge

F.C.= # valence e- -lone pairs- - 1/2 bonding e- (or single bonds)

Molecule

Formed when two or more atoms join together chemically.

Odd electron

If there is an odd number of valence electrons, it is not possible to give every atom eight electrons

Polyatomic Ions

Ions composed of two or more atoms bonded wogether with an overall positive or negative charge. Examples: -NH4+ ammonium ion -SO42- sulfate

Monatomic ions

Ions consisting of a single charged atom. e.g. H-

Ionic bonding

Representative element form ions that obey the octet rule. Ions of opposite charge attract each other creating the ionic bond. Electrons are lost by a metal and they are gained by a nonmetal. -Each aton achives a noble gas configuration -TWO ions form: a cation (+) and an anion (-) , which are attracted to each other.

Writing Names of Ionic Compounds from the Formula of the Compound

Roman numerals give the charge of the metal -FeCL2 is iron (II) cloride -Fe CL3 is iron (III) chloride -Cu2O is iron (I) chloride -CuO is copper (II) oxide

Electronegativity calculations

The greater the difference in EN bwteen two atoms , the greater the polarity of their bond. Nopolar: ≤ 0.4 Polar: -for two non-metals 0.4<EN>2 -for metal and non-metals 0.4<EN>1.5 Ionic bond: -for two non-metals EN>2 -for metals and non-metal EN>1.5

Chemical bond

The net (overall) force of attraction between any atons or ions

Bond Polarity

When two atoms bonds, the diffrence in their EN determines the polarity of the bond that forms between them. -One extreme are ionic bonds, in which the difference in EN is so large that electrons are fully tranferred from one atom to the other. -The other extreme are covalent bonds, where there is an EQUAL SHARING of electrons between the two atoms ( EN values are the same) -In between these two extremes are polar covalent bonds, in which there is an UNEQUAL SHARING of electrons between the two bonded atoms.

Lewis symbol

chemical symbol of an element surrounded by dots equal in number to the number of valence electrons present in the atoms of the element. -for covalent compounds place least EN atom as the central atom.

Metals

metals tend to form cations because they have low I.E.( they easily lose electrons) and low E.A. (they don't realise much energy upon accepting electrons)

Nonmetals

non-metals tend to form anions because tehy have high I.E (they DON'T easily lose electrons) and high E.A (they release a large amount of energy upon accepting electrons)

Bond energry

the amount of energy required to break a bond holding two atoms together; a measure of the stregth of a bond. triple bond>double bond>single bond

Bond Length

the distance separating the nuclei of two adjacent atoms single bond>double bond>triple bond

H20

water

Resonance structure

when two or more Lewis structures contribute to the real structure -NONE of them is an accurate representation of the real compound, but rether an "average", or resonance hybrid, is what the structure of the compound is truly like.