Covalent Compounds (Chapter 6)

Question 1

How does a covalent bond form between two atoms?

Answer 1

A covalent bond forms when two or more valence electrons are attracted y the positively charged nuclei of two atoms and thus are shared between both atoms

Question 2

Explain why H2 being more stable than two separate H atoms does or does not hold true for most covalent bonds

Answer 2

Molecules are stable when they achieve a noble gas configuration with an outer shell of 8 electrons. Hydrogen is the exception to this rule since it achieves a noble gas configuration when it has two electrons in its outer shell

Question 3

How does a covalent bond differ from an ionic bond?

Answer 3

In a covalent bond, atoms share one or more pairs of electrons. In an ionic bond, one atom transfers electrons to another

Question 4

What is a molecular orbital?

Answer 4

A molecular orbital is a region in which there is high probability that an individual electron exists as it travels with a wavelike motion in the three-dimensional space around one f two or more associated nuclei

Question 5

Describe the potential energy change that occurs when two hydrogen atoms approach each other and form a covalent bond

Answer 5

When two hydrogen atoms approach each other, the potential energy of the combination becomes ower and lower until it reaches a minium value of -436 kJ/mol at a distance of 75 pm

Question 6

In terms of energy, why is the H-H bond stable?

Answer 6

As a covalent bond forms between two hydrogen atoms, the atoms reach a distance from each other at which attractive and repulsive forces are balanced and the total energy of the system is at a minimum. At this minimum energy state, the molecule is the most stable

Question 7

Describe the typical properties of substances that have metallic, ionic, and covalent bonds

Answer 7

Metallic bonds: Average melting and boiling points, soft, silvery, and solid, conducts electricity as a solid
Ionic bonds: High melting and boiling points, crystalline, white solid, conducts electricity when dissolved in water
Covalent bonds: low melting and boiling points, usually a liquid or a gas, not a good conductor of electricity

Question 8

What is resonance?

Answer 8

When a double bond can be in more than 1 place around the central atom

Question 9

What are the prefixes put in front of atoms when they’re covalent?

Answer 9

1 - mono
2 - di
3 - tri
4 - tetra
5 - penta
6 - hexa
7 - hepta
8 - octa
9 - nona
10 - deca

Question 10

What does the VSEPR theory predict?

Answer 10

VSEPR theory predicts the general shape of a molecule based on its Lewis structure

Question 11

How does one unbonded pair of electrons affect the shape of a molecule?

Answer 11

The electrons in the unbonded pair repel bonding electrons as far away as possible from it

Question 12

How do multiple unbonded pairs of electrons affect the shape of a molecule?

Answer 12

Multiple unbonded pairs of electrons, as in the oxygen atom of H20, can repel each other aw well as bonding electrons, and form a bent molecule

Question 13

What evidence is there to support the idea that opposite polar ends of molecules attract each other?

Answer 13

The energy required to separate polar molecules is greater than that required to separate nonpolar molecules

Question 14

How do polarity and shape of molecules relate to the properties of a substance?

Answer 14

Shape and polarity can affect how a molecule fits into another structure and how it tastes. It can affect how easy the molecule is to separate and its attraction to positively or negatively charged objects