Crux of the Matter Unit 4

Chapters 7 and 8

Ionic Compounds

• A transfer of electrons creates a strong bond• Occurs between a metal and a nonmetal or a

metal and a polyatomic ion- held together by electrostatic force

• Compounds form in the simplest whole number ratios

• Creates true ions- cation (+) and anion (-)• All ionic compounds are polar and called a

formula unit• Alkali and alkaline metal compounds combined

with halogens are called salts

Properties of Ionic Compounds

• Compounds are solids at room temperature• Crystalline solids (made of ions) 6 basic

shapes • High melting and boiling points – due to the

lattice energy- smaller the ions involved the stronger the bonds

• Conduct electricity when melted or dissolved in water- electrolytes

Properties Continued

• Many soluble in water ( the universal polar solvent) but not in nonpolar liquid

• The formation of ionic compounds is always exothermic

Criss Cross

Naming ionic compounds

Lewis Dot Diagrams of Ionic Compounds

Covalent Compounds

• Created from sharing electrons• Occurs between a nonmetal and a nonmetal or a

nonmetal and a polyatomic ion• Covalent compounds can either be polar or

nonpolar• Covalent compounds are called molecules• Formulas are in whole number ratios, but do not

need to be simplified• There can be single, double and triple bonds• Diatomic elements-OHNoHalogens

Properties of covalent compounds

• Bonds have different lengths- the shorter the bond the more energy required to break it

• Triple bonds are stronger than double bonds, and double bonds are stronger than single bonds

• Compounds are usually gases or liquids, some however can be solids

• Low melting and boiling points than ionic compounds • Poor electrical conductors in all phases • Compounds are either polar or nonpolar- to dissolve, use the rule

“like dissolves like”

A molecule’s shape

Lewis Dot Diagrams and Structural Diagrams

Total Pairs Electrons Shared Pairs Unshared Pairs General Shape

4 4 0 tetrahedral

4 3 1 pyramidal

4 2 2 bent

4 1 3 linear

3 3 0 trigonal planar

3 2 1 bent

3 1 2 linear

2 2 0 linear

2 1 1 linear

1 1 0 linear

Determining a molecule’s shape

Hybridization

Determining the polarity of a molecule

Naming Molecules

Naming Acids

Resonance Structures occur when molecules can arrange themselves to form bonds in different areas yet still obey the octect rule.

Metallic Bonds occur because the metals’ nuclei becomes surrounded by a sea of electronThis gives metals their physical properties of malleability and ductility

• Hydrogen Bonds-occur between hydrogen and a higher electronegative element (O,N, halogens)

• Dipole bonds- created from equal but opposite charges

• London dispersion forces-weak intermolecular forces that occur between nonpolar molecules and is caused by the movement of electrons