Ch 6 Chemical Bonding

A chemical bond is a mutual electrical attraction between the nuclei and valence electrons of different atoms that binds the

atoms together.

Two types of Bonding• Ionic bonding: Atoms completely give up

electrons to the other atom. (transfer of electrons)

• Covalent bonding: results in a sharing of electrons between two atoms.

Recall Electronegativity:

• Electronegativity is a measure of an atom’s ability to attract electrons.

• Bonding between the same atoms is purely covalent. (attraction of the electrons is the same for both atoms)

• Ex: Cl2

Table of Electronegativities

Polar and Non-polar

• Atoms with an electronegativity difference of 0 to 0.3 are considered to form non-polar covalent bonds.

• A non-polar covalent bond is where the electrons are shared equally between the two atoms.

• Atoms with an electronegativity difference of 0.3 to 1.7 are considered to form polar covalent bonds.

• Polar covalent bonds have one atom with a greater share of the valence electrons.

• Atoms with an electronegativity difference greater than 1.7 are considered to form ionic bonds.

• Ionic bonds have one atom hogging the entire bonding electrons and will have an effective negative charge and one atom without any bonding electrons sitting with a positive charge.

• The electronegativity difference between chlorine and hydrogen is 3.0 – 2.1 = 0.9, indicating a polar covalent bond. Electrons are closer to the chlorine, making chlorine the more negative ion.

• Use electronegativities to classify the bond type and the more negative ion.

Ions bond type more negative ionSulfur and hydrogen2.5 – 2.1 = 0.4 polar-covalent sulfurSulfur and cesium2.5 – 0.7 = 1.8 ionic sulfurSulfur and chlorine2.5 – 3.0 = 0.5 polar covalent chlorineNitrogen and bromine3.0 – 2.8 = 0.2 non-polar covalent nitrogen

• p. 163: # 3• p. 196: #33

• A double covalent bond is a covalent bond produced by the sharing of two pairs of electrons between two atoms.

• Ethene C2H4

H H H H

• C C or C C• H HH H

• A triple bond is the sharing of three pairs of electrons between two atoms. Ex. N2

• N N or N N

• p 175 # 4• p 196 # 39, # 41