chapter 10 chemical bonding

Lewis symbols for main-group elements

show valence electrons as dots around the element symbol.

lewis symbols and ionic compounds

opposite charges attract.

Cation

metal looses electron

anion

nonmetal gain electrons

What happens to lattice energy when the charges of ions increase?

Lattice energy gets larger.

What happens to lattice energy when the size of ions decreases?

Lattice energy gets larger.

What combination results in the strongest ionic attraction?

High charge and small radius.

What is a pure covalent bond?

Equal sharing of electrons between the same atoms.

What is a polar covalent bond?

Unequal sharing of electrons.

What characterizes an ionic bond?

Electron transfer, usually between a metal and a nonmetal.

What does a very small electronegativity difference indicate?

Nonpolar covalent bond.

What does a moderate electronegativity difference indicate?

Polar covalent bond.

What does a large electronegativity difference indicate?

Ionic bond.

Lewis structures for molecules and polyatomic ions

Steps:

Draw skeletal structure

Count total valence electrons

Place single bonds

Complete terminal atom octets

Put leftover electrons on central atom

Make multiple bonds if needed for octets

Formal charge

FC=valence e− −nonbonding e− −1/2(bonding e−)

Best Lewis structure:

smallest formal charges

negative formal charge on more electronegative atom when possible

What is an incomplete octet?

Elements that are stable with fewer than 8 electrons in their valence shell, such as H (2), He (2), Li (2), Be (4), and B (6).

What is an expanded octet?

Elements in period 3 or greater can hold more than 8 electrons in their valence shell, such as P (10), S (12), and Cl (14).

What happens to elements with an odd number of electrons?

Any element with an odd number of electrons won't be able to distribute electrons to give 8 to each atom.

What is the relationship between bond strength and bond energy?

Stronger bond → larger bond energy

What is the relationship between bond strength and bond length?

Stronger bond → shorter bond length

Which type of bond is stronger: triple, double, or single?

Triple bonds are stronger than double bonds, which are stronger than single bonds.

Which type of bond is shorter: triple, double, or single?

Triple bonds are shorter than double bonds, which are shorter than single bonds.

bond energy calculation

ΔH≈∑(bonds broken)−∑(bonds formed)

Remember:

Breaking bonds requires energy

Forming bonds releases energy