Valence And Ionic & Covalent Bonds

Question 1

Define bond.

Answer 1

Forces that hold atoms together.

Question 2

Define covalent bond.

Answer 2

A bond where two atoms share electrons.

Question 3

Define ionic bond.

Answer 3

A bond between a metal and non-metal.

Question 4

Define electronegativity.

Answer 4

An atoms ability to attract electrons in a chemical bond.

Question 5

Define empirical formula.

Answer 5

The simplest ratio of atoms.

Question 6

Why don’t noble gases have electronegativity?

Answer 6

Because they have a full outer shell.

Question 7

Define ΔEN.

Answer 7

Difference in electronegativity.

Question 8

To predict what type of bond will form you need to work out ΔEN. How is this done?

Answer 8

EN_{(Element 1)} - EN_{(Element 2)} = ΔEN

Question 9

What is the ΔEN value for ionic bonds?

Answer 9

More than 2.1

Question 10

What is the ΔEN value for polar covalent bonds?

Answer 10

0.4 to 2.1

Question 11

What is the ΔEN value for non-polar covalent bonds?

Answer 11

Less than 0.4

Question 12

Define δ-

Answer 12

It means delta negative and gain of electron density.

Question 13

Define δ+

Answer 13

It means delta positve and loss of electron density.

Question 14

Define deshielding.

Answer 14

When the electrons aren’t shared equally as a polar covalent bond is formed.

Question 15

What does this diagram represent?

Answer 15

A polar covalent bond has formed. The arrow represents a dipole directing to the more electronegative element.

Question 16

What are the three rules for drawing Lewis structures?

Answer 16

1. Count the valence electrons (number of outer electrons).
2. Use two electrons to form a covalent bond.
3. Use remaining electrons to yield full valency for all atoms.

Question 17

Define duet rule.

Answer 17

Full valency of the first shell, which is two electrons.

Question 18

Define octet rule.

Answer 18

Full valency of the outer shell, which is eight electrons.

Question 19

How many bonds can Hydrogen make?

Answer 19

One.

Question 20

The octet rule applies to which four elements?

Answer 20

Carbon, Nitrogen, Oxygen and Fluorine as they cannot exceed eight electrons.

Question 21

What four elements can have less electrons than the octet rule?

Answer 21

Beryllium, Magnesium, Boron and Aluminium.

Question 22

What two elements can have the same or more electrons than the octet rule?

Answer 22

Phosphate and Sulphur.

Question 23

Define structural isomers.

Answer 23

Same molecular formula, but different gross connectivity.

Question 24

Define geometric isomers.

Answer 24

Same gross connectivity, but different orientation in space due to no rotation about double bond.

Question 25

Define saturated.

Answer 25

C_nH_2n+2

Question 26

Define unsaturated.

Answer 26

C_nH_2n

Question 27

Define valency.

Answer 27

The potential of an atom of an element to combine with other atoms measured by the number of electrons which an atom will give, take or share to form a chemical bond.

Question 28

Define postive valence.

Answer 28

Valence electrons are donated.

Question 29

Define negative valence.

Answer 29

Valence electrons are accepted.

Question 30

Define ionisation energy.

Answer 30

The energy required to remove a valence electron from a given atom.

Question 31

If an atom has high ionisation energy, are the valence electrons easier or harder to remove?

Answer 31

Harder.

Question 32

If an atom has small ionisation energy, are the valence electrons easier or harder to remove?

Answer 32

Easier.

Question 33

How many times stronger is a covalent bond than an ionic bond?

Answer 33

5 to 20 times stronger.

Question 34

What do ionic bonds exist as at the molecular level?

Answer 34

Crystal lattice.

Question 35

What percentage of cells are water?

Answer 35

70%.

Question 36

Define bond length.

Answer 36

The distance at the lowest energy point is the separation between the atoms at which their attraction is maximal.

Question 37

Who is regarded as the founder of modern Biology and Chemistry?

Answer 37

Linus Pauling.

Question 38

Who developed the concept of the “chemical bond” and “molecular biology” in the 1940’s?

Answer 38

Linus Pauling.