Chapter 6 Study Guide - Chemical Bonding

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Section One

Intro to Chemical Bonding

chemical bonds exist because atoms rarely exist alone

when atoms bond together they have less potential energy and are MORE stable (they are happier)

Atoms lower their energy or become happier by....

1. losing electrons

2. gaining electrons

3. sharing electrons

to obtain a noble gas electron configuration ( full p^6 sublevel)

Chemical bond: mutual electrical attraction between the nuclei (+) and valence electrons (-) of diff. atoms that binds the atoms together

Ionic bonding - attraction between cations (+) and anions (-). Electrons are transferred between atoms.

Covalent bonding - result from sharing of electron pairs between two atoms. Electrons shared belong to both atoms!

* polar - uneven sharing

*nonpolar - even sharing

IONIC OR COVALENT? ESTIMATE BY CALCULATING THE ELEMENTS' ELECTRONEGATIVITIES

electronegativity: measure of an atoms ability to attract electrons

Bond Types - electronegativity

COVALENT

nonpolar 0 - .3

polar .4 - 1.6

IONIC

1.7 - 4.0

*As you go across a period on the periodic table (row) electronegativity values increase, as you go downwards they decrease ( doesn't apply to noble gasses)

*Fluorine is the most electronegative atom

Patterns

metals + nonmetals = ionic bond

nonmetals + nonmetals = covalent bond

metal + metal = metallic bond

Section Two

Covalent Bonding and Molecular Compunds

Molecule - neutral group of covalently bonded atoms

(most likely occurs between a metal and a nonmetal)

Example: O2. Two atoms of oxygen.

Molecular Compound - chemical compound whose simplest units are molecules.

Example: H20. This is a compound because two diff. atoms are combined. Three atoms bonded together.

Molecular Formula - shows the types & numbers of atoms combined in a single molecule of a molecular compound.

Chemical Formula - simplest way to represent atoms bonded together.

The Octet Rule

Compounds want to get 8 electrons around their nucleus. This is most stable for the compound.

*Boron & Aluminium only need 6 electrons! (group 13, 3 valence electrons)

Phosphorus & Sulfur can have greater than 8 if bonded to a highly electronegative element (such as chlorine, oxygen, fluorine).

Electron-dot notation - dots represent the valence electrons of an element

Lewis Dot notation

1. Determine type & number of atoms in molecule

2. electron dot notation for each atom in molecule

3. total number of valence electrons

4. arrange atoms so lone electrons line up

5. lines represent shared electrons, add unshared electron pair to each nonmetal (except H) to GET 8!

HONC rule

Hydrogen and Halogens form 1 bond

Oxygen family form 2 bonds

Nitrogen family form 3 bonds

Carbon family form 4 bonds