Covalent BondsDue 11/21/13

http://tinyurl.com/mp7wlpw

Objectives

• Draw the structure for covalent compounds using the NASL method or the conceptual method

• Show ALL work for ALL examples!

Covalent Bonds• 2 Nonmetals• Atoms have equal electron affinity, therefore one

atom is unlikely to accept an electron from another• High ionization energy so atoms are unlikely to lose

electrons• Atoms are bonded by a pair of electrons shared

between them• Represented by a pair of dots (electrons) between

two Lewis symbols

N.A.S.L. Method – Step 1

Example: Carbon Tetrachloride - CCl1. Place the least electronegative atom in the

center (never hydrogen)

N.A.S.L. Method – Step 2

2. Needed – Sum of the electrons needed for each atom to achieve its octet. N = 8 for representative elements with the exception of H-2, He-2, Be-4, B-6

N.A.S.L. Method – Step 3

3. Available – Add the number of valence electrons from each atom.

N.A.S.L. Method – Step 4

4. Shared – Needed – Available. To determine the number of bonds, divide the number of shared electrons by 2.

N.A.S.L. Method – Step 5

5. Lone Pair Electrons – Available - Shared. Divide this number by 2 to get the number of lone pairs and distribute between appropriate terminal atoms to fulfill each atom’s octet

Conceptual Method4A 5A 6A 7A Hydrogen

Common Elements

C, Si N, P, As O, S F, Cl, Br, I H

# Bonds

# Lone pairs

Options

Practice 1

• Carbon Dioxide – CO2

Practice 2

• Ammonia – NH3

Questions?