Chemical Bonding SCH4C Ms. Richardson

Chemical Bonding Atoms bond with other atoms in order to become stable. Atoms become stable when they lose, gain or share valence electrons in order to obtain a full outer orbit or energy level. A full outer orbit is called a stable octet.

Ionic Bonds Ionization Equation: Na  Na+ + 1e- Cl + 1e-  Cl- Na + Cl + 1e-  Na+ + 1e- + Cl- (cancel out the electrons that appear on both sides of the equation) In ionic bonds, electrons are transferred from a metal atom to a non-metal atom. The two oppositely charged ions attract to each other.

Ionic Bonds Ionization Equation: Mg  Mg2+ + 2e- F + e-  F- Mg + 2F + 2e-  Mg2+ + 2e- + 2F- Mg + 2F  Mg2+ + 2F- Remember that the number of electrons lost must equal the number of electrons gained. In this example, we need to multiply the 2nd equation

Covalent Bonding A covalent bond occurs when 2 atoms share a pair of electrons. Lewis Diagram Lewis Structure Note that the electrons are shared equally. This results in a non-polar covalent bond.

Polar Covalent Bonds Sometimes there is unequal sharing of a pair of electrons. The atom that has a greater ‘hold’ on electrons will be slightly negative (δ-) and the other atom will be slightly positive (δ+). δ+ δ-

Predicting Bond Types Electronegativity (EN) measures the ability of an atom to attract electrons. Fluorine has the highest EN. We can determine the type of bond that forms between two atoms by comparing the electronegativity value of each of the 2 elements involved

Bonding Continuum EN =  EN1 – EN2  Always find the absolute value – your answer will never be negative!!

Predicting Bond Type Example: F2 EN =  EN1 – EN2  = 4.0 – 4.0 = 0 Therefore, the bond is non-polar covalent.