Chemical Bonding

• chemical bonding = interaction of electrons

• when elements form compounds, they become stable

  • full valence shell (octet rule)

Types of Bonding

Ionic

1. metal + non metal

2. electrons transferred from metal to nonmetal (high EA)

3. opposite charges attract, form electrostatic attraction

• hard to break

Rules for Naming

• write name of metal first

• name of non metal next, change ending to ‘ide’

  • ex. Na + Cl → sodium chloride

Rules for Making Chemical Formulas

• crossover method = bring down ionic charges above the metal and non metal to opposite sides

• zero sum rule = sum of all positives and negatives must be zero

1. write metal and non metal symbols

2. write ionic charge above each symbol

3. use cross over rule to cross numbers down and over

4. reduce subscripts if necessary

5. use zero sum rule to ensure compound is neutral

Covalent

1. non metal + non metal

2. share electrons

3. shared pair is the bond

• easy to break

Covalent Naming and Formula

• name of the elements is preceded by a prefix

  • prefix of first element is omitted if it is mono

• name of other atom ends with ‘ide’

• NH3-ammonia (nitrogen trihydride), CH4-methane (carbon tetrahydride), H2O2 hydrogen peroxide (dihydrogen dioxide)

Electronegativity

• measure of an atoms ability to attract electrons in a bond

• higher the number on EN chart, greater an elements EN

Periodic Trends

• increases across a period

• decreases down a group

• follows EA

• related to AR

  • small AR, increased FOA

    • electrons move closer to nucleus (same for EN)

Bond Types using EN values

• EN values determine whether a bond is ionic or covalent (molecular)

• greater the difference in electronegativities, greater the chances the electrons will be transferred

  • transferred = ionic bond

1. Find EN values for both elements in the bond

2. Subtract smaller number from the larger number (result is positive)

   1. result > 1.7 = ionic

   2. result < 1.7 = covalent