Chemical bonding theories

Question 1

Define ‘chemical bond’

Answer 1

The forces that hold atoms together to form molecules

Question 2

How does the force that holds atoms together occur?

Answer 2

The valence electrons of one atom is attracted to the nucleus of the other atom. The repulsion between the two electrons and two nuclei are relatively small, so the attraction results in a force that keeps the atoms together.

Question 3

How are ionic bonds formed?

Answer 3

An electron or multiple electrons from the valence shell of an atom is transferred to the valence shell of another atom. The atom that loses an electron becomes a cation, and the atom that gains an electron becomes an anion. The opposite charges of the ions result in an electrostatic attraction between them and forms an ionic bond.

Question 4

Define ‘covalent bonds’

Answer 4

Strong attractive forces that hold two atoms together by their sharing of electrons.

Question 5

How do covalent bonds occur?

Answer 5

The nuclei of two different atoms both attract the shared electrons, which holds them together.

Question 6

What is a non-polar covalent bond?

Answer 6

Covalent bonds in which the bonding electrons are equally shared between the bonded atoms. Occurs between atoms of equal or comparable electronegativities.

Question 7

What is a polar covalent bond?

Answer 7

Covalent bonds in which there is unequal sharing of electrons due to a difference in electronegativities of the two atoms. The bonding electrons are attracted simultaneously to both nuclei, but spend more time near the atom with the higher electronegativity.

Question 8

Difference in electronegativity interval for different types of chemical bonds.

Answer 8

> 1.7 ionic
<1.7 polar covalent
~0 non-polar covalent

Question 9

What is a coordinate covalent bond?

Answer 9

Covalent bonds between two atoms in which both electrons that form the bond come from the same atom.

Question 10

Chemical reactions involve the movement of valence electrons from a region of __(a)__ to a region of __(b)__.

Answer 10

a) high electron density
b) low electron density

Question 11

In any chemical reaction, the more __(a)__ elements tend to gain electrons to attain the __(b)__, while __(c)__ elements tend to lose electrons to attain __(b)__.

Answer 11

a) electronegative
b) noble gas configuration
c) electropositive

Question 12

How do we indicate the movement of electrons?

Answer 12

Half-headed curved arrow - one electron
Full-headed curved arrow - two electrons