Covalent Bonding

1/19/12

• Objective: To explore multiple covalent bonding

• Do Now: On a sheet of paper, write the definition of an ionic bond and a covalent bond. (4 min)– For each kind of bond, give an example of a

compound held together by those bonds.

• Do Later: Finish covalent bonding challenge puzzles

Covalent bonds

• Bonds in which two atoms share a pair of valence electrons.

• Two or more atoms held together by covalent bonds form a molecule.

H

H2

H

Octet rule revisited• Recall: The purpose of bonding is to acquire a

full valence shell– Ionic bonds: NaCl

– Covalent bonds: H2O, CH4

Double bonds

• Two atoms can share more than one covalent bond

• In a double bond, two pairs of electrons are shared

Triple bonds

• In a triple bond, three pairs of electrons are shared

Triple bond (N2)

Bonding Capacity• In each covalent bond, an atom – 1) shares a valence electron with its partner– 2) gets a new valence electron shared with it.

• Atoms need to have at least one of their own valence electrons for every covalent bond they form.

Single bond

Practice problem

• How many valence electrons does boron have?

• What’s the maximum number of covalent bonds boron can form?

Practice problem

• Can boron ever achieve a valence octet by covalent bonding?– No!

Bonding capacity

• For each covalent bond an atom forms, it must have an empty space in its valence shell to receive a new electron.– Fluorine has one empty space in its valence shell,

so it can only form one covalent bond

Practice problem

• What is the maximum number of covalent bonds the following elements can form? – Chlorine– Oxygen– Bromine– Nitrogen– Polonium

Bonding capacity

• The bottom line: – For each covalent bond an atom forms, it must

have:1) A valence electron to share and 2) a vacancy in its valence shell to accept a new electron.

Practice problem

• Fill in this table in your notes: Element Atomic # Valence e-s Vacancies in

valence shellBonding capacity

Hydrogen 1

Carbon 6

Nitrogen 7

Oxygen 8

Ammonia Water

Methane