Chapt 4 Homework Questions

Question 1

What is a covalent bond, and how does it differ from an ionic bond?

Answer 1

A covalent bond is a chemical bond in which two electrons are shared between atoms.

With an ionic bond, the electrons are not shared, instead they are held together with electrostatic attraction (between the positive charge of one ion and the negative charge of another)

Question 2

What is a coordinate covalent bond and how does it differ from a covalent bond?

Answer 2

In a coordinate covalent bond, both electrons in the bond came from the same atom.

Question 3

Identify the bonds formed as covalent or ionic?

a) Carbon and Hydrogen

Answer 3

both are non-metals= covalent bond

Question 4

Identify the bonds formed as covalent or ionic?

b) Carbon and Oxygen

Answer 4

both are non-metals= covalent bond

Question 5

Identify the bonds formed as covalent or ionic?

c) Carbon and Nitrogen

Answer 5

both are non-metals= covalent bond

Question 6

Identify the bonds formed as covalent or ionic?

d) Carbon and Fluorine

Answer 6

both are non-metals= covalent bond

Question 7

Identify the bonds formed as covalent or ionic?

e) Oxygen and Hydrogen

Answer 7

both are non-metals= covalent bond

Question 8

Look up tellurium (Z = 52) in the periodic table and predict how many covalent bonds it is likely to form

Answer 8

Tellurium is in row 6A (or 16) and is in the same row as oxygen and sulfur. All of the atoms in this row have two unpaired valence electrons and like to form only 2 covalent bonds.

Question 9

Distinguish between the following:

A molecular formula and a structural formula

Answer 9

A molecular formula only provides you with the elements in the compound and how many atoms of each element are present. It does not provide any additional information.

A structural formula shows how each atom is bonded together.

Question 10

Distinguish between the following:

A structural formula and a condensed structure

Answer 10

A structural formula shows how each atom is bonded together.

A condensed structure does not show the bonds but is understood by the order in which the atoms are written.

Question 11

Distinguish between the following:
A lone pair of electrons and a bonded (or shared) pair of
electrons.

Answer 11

A lone pair of electrons is not shared lies only on one atom and is not shared with any other atoms.

A shared pair of electrons (or a bonded pair) are electrons that are shared between two atoms and are used in forming a covalent bond between two molecules.

Question 12

Determine the total number of valence electrons in the following molecules. If the molecule contains multiple bonds, indicate where the multiple bonds are located and whether they are double or triple bonds:

N2

Answer 12

Each nitrogen contains 5 valence electrons:

10 valence electrons total

Triple bond between the nitrogen atoms

Question 13

Determine the total number of valence electrons in the following molecules. If the molecule contains multiple bonds, indicate where the multiple bonds are located and whether they are double or triple bonds:

CH3COOH

Answer 13

Carbon: (4e-x 2) = 8 valence electrons

Hydrogen: (1e-x 4) = 4 valence electrons

Oxygen: (6e-x 2) = 12 valence electrons

24 valence electrons total

Double bond between the carbon and
oxygen atoms.

Question 14

Determine the total number of valence electrons in the following molecules. If the molecule contains multiple bonds, indicate where the multiple bonds are located and whether they are double or triple bonds:

CH3CH2CHO

Answer 14

Carbon: (4e-x 3) = 12 valence electrons

Hydrogen: (1e-x 6) = 6 valence electrons

Oxygen: (6e-x 1) = 6 valence electrons

24 valence electrons total

Double bond between the carbon and
oxygen atoms.

Question 15

Determine the total number of valence electrons in the following molecules. If the molecule contains multiple bonds, indicate where the multiple bonds are located and whether they are double or triple bonds:

OF2

Answer 15

Oxygen: (6e-x 1) = 6 valence electrons

Fluorine: (7e-x 2) = 14 valence electrons

20 valence electrons total

No multiple bonds

Question 16

Determine the total number of valence electrons in the following molecules. If the molecule contains multiple bonds, indicate where the multiple bonds are located and whether they are double or triple bonds:

OF2

Answer 16

Oxygen: (6e-x 1) = 6 valence electrons

Fluorine: (7e-x 2) = 14 valence electrons

20 valence electrons total

No multiple bonds

Question 17

If a research paper appeared reporting the structure of a new molecule with the formula C2H8, most chemists would be highly skeptical. Why?

Answer 17

Too Many Hydrogens. There is no way that all of the atoms can be connected together with covalent bonds and follow the octet rule.
Carbon can only form 4 bonds, hydrogen can only form one bond.
The structure of C2H8 would assume that each carbon has 10 valence electrons.
The s and p suborbitals of carbon can only hold 8 electrons total (2 for the 2s and 6 for the 2p). The structure below is simply not possible.