Hydrogen and Chlorine: Covalent Bonding: H Cl or H-Cl H + Cl Sharing electrons 2) Hydrogen & hydrogen. (Single covalent bond) 3) Fluorine & fluorine. 4) Nitrogen & hydrogen. 5) Carbon & hydrogen.

Covalent Bonding: The Octet Rule in Covalent Bonding In covalent bonds, electron sharing usually occurs so that atoms attain the electron configurations of noble gases. The pair of shared electrons forming the covalent bond is also often represented as a dash, as in H—H for hydrogen (structural formula )

Covalent Bonding: Represent the formation of the chemical bond between the following atoms (Lewis dot structure): 1)Oxygen and oxygen: Two pairs of electrons shared or O=O O O O + O (Double covalent bond) A double covalent bond is a bond that involves two shared pairs of electrons.

Three pairs of electrons shared 2) Nitrogen & nitrogen: N + N or N N N N Three pairs of electrons shared (Triple covalent bond) A bond formed by sharing three pairs of electrons is a triple covalent bond.

Using electron-dots structure represent the following molecules: CO2 2) C2H4 3) C2H2

How do electronegativity values determine the charge Bond Polarity: How do electronegativity values determine the charge distribution in a polar bond? Remember, the electronegativity indicates the relative ability of each atom to attract electrons in a chemical bond.

Bond Polarity The nuclei of atoms pull on the shared electrons , much as the knot in the rope is pulled toward opposing sides in a tug-of-war.

Bond Polarity A polar covalent bond, known also as a polar bond, is a covalent bond between atoms in which the electrons are shared unequally. The more electronegative atom attracts more strongly and gains a slightly negative charge. The less electronegative atom has a slightly positive charge. δ+ δ– H—Cl Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Bond Polarity H-H Br-Br O=O When the atoms in the bond pull equally (as occurs when identical atoms are bonded), the bonding electrons are shared equally, and each bond formed is a nonpolar covalent bond. H-H Br-Br O=O Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Bond Polarity The electronegativity difference between two atoms tells you what kind of bond is likely to form. Electronegativity Differences and Bond Types Electronegativity difference range Most probable type of bond Example 0.0 – 0.39 Nonpolar covalent H—H (0.0) 0.4 – 0.9 Moderately polar covalent δ+ δ– H—Cl (0.9) 1.0 – 1.9 >1.5 Very polar covalent Ionic (if a metal is present) H—F (1.9) ≥ 2.0 Ionic Na+Cl– (2.1) Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Sample Problem Identifying Bond Type Which type of bond (nonpolar covalent, moderately polar covalent, very polar covalent, or ionic) will form between each of the following pairs of atoms? a. N and H b. F and F c. Ca and Cl d. Al and Cl

Moderately polar covalent. Electronegativity Differences and Bond Types Electronegativity difference range Most probable type of bond Example 0.0 – 0.39 Nonpolar covalent H—H (0.0) 0.4 – 0.9 Moderately polar covalent δ+ δ– H—Cl (0.9) 1.0 – 1.9 >1.5 Very polar covalent Ionic (if a metal is present) H—F (1.9) ≥ 2.0 Ionic Na+Cl– (2.1) a. 3.0(N) - 2.1(H) = 0.9 Moderately polar covalent. b. 4.0(F) - 4.0(F) = 0.0 Nonpolar covalent. c. 3.0(Cl) - 1.0(Ca) = 2.0 Ionic. d. 3.0(Cl) - 1.5(Al) = 1.5 Very polar covalent. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

A molecule that has two poles is called a dipolar molecule, or dipole. Describing Polar Covalent Molecules: In a polar molecule, one end of the molecule is slightly negative, and the other end is slightly positive. δ+ δ- A molecule that has two poles is called a dipolar molecule, or dipole. Example: δ+ δ– H—Cl Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

A carbon dioxide molecule has two polar bonds, it is linear. O C O The effect of polar bonds on the polarity of an entire molecule depends on the shape of the molecule and the orientation of the polar bonds. A carbon dioxide molecule has two polar bonds, it is linear. O C O Therefore, the molecule is nonpolar. (The bond polarities cancel). Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

The water molecule also has two polar bonds. However, the water molecule is bent rather than linear. Therefore, the bond polarities do not cancel and a water molecule is polar. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.