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: Cl 2

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. Ionsbond typemore negative ion Sulfur and hydrogen 2.5 – 2.1 = 0.4polar-covalentsulfur Sulfur and cesium 2.5 – 0.7 = 1.8ionicsulfur Sulfur and chlorine 2.5 – 3.0 = 0.5polar covalentchlorine Nitrogen and bromine 3.0 – 2.8 = 0.2non-polar covalentnitrogen

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 C 2 H 4 H HH H C CorC C H HH H

A triple bond is the sharing of three pairs of electrons between two atoms. Ex. N 2 N Nor N N p 175 # 4 p 196 # 39, # 41