Chemistry Unit 4 - Bonding

Question 1

What is a chemical bond?

Answer 1

Attractive force that holds two or more atoms together

Question 2

Why do atoms combine to chemically bond?

Answer 2

When atoms bond, there is a lowering of the overall energy state of atoms. Formation of a system that has lower energy leads to greater stability.

Question 3

What types of elements create Metallic Bonds?

Answer 3

Metals or alloys (mixture of metals)

Question 4

What are metallic bonds?

Answer 4

An attractive force between delocalized electrons and the positive nuclei of all metal atoms

Question 5

Why do metals have a high MP, BP, and are solid at room temperature?

Answer 5

Bond between delocalized sea of electrons and atoms is very strong, so it requires a lot of energy to be broken (change states)

Question 6

Why are metals conductive of electricity and heat?

Answer 6

Delocalized electrons can carry current and energy throughout the whole structure easily

Question 7

Why are metals malleable and ductile?

Answer 7

Layers of atoms can slide past each other because bond can be broken/reformed easily

Question 8

What types of elements create covalent bonds?

Answer 8

Nonmetals

Question 9

What is a covalent bond?

Answer 9

A covalent bond is an attractive force between the nucleus of one atom and the electrons of the other (valence electrons are shared between atoms)

Question 10

What is a covalent nonpolar bond?

Answer 10

Electrons are shared equally, no one atom’s nucleus is pulling on the other’s electrons more because they have the same or very little difference in electronegativities (EN value difference of 0.4)

Question 11

What is covalent polar bond?

Answer 11

Electrons are shared unequally, one atom’s nucleus is pulling on the other’s electrons more because they have a large difference in electronegativities (EN value difference of 0.5 or greater)

Question 12

What types of elements form an Ionic Bond?

Answer 12

Metals and nonmetals

Question 13

What is an ionic bond?

Answer 13

An electrostatic attractive force between the cation and the anion

Question 14

What happens to form an ionic bond?

Answer 14

A high EN atom will pull away the loosely held valence electron of an atom with low EN –> metals valence electrons are transferred to the nonmetal’s valence shell

Question 15

Which groups and types of elements form cations?

Answer 15

Metals form cations - Group #1,2, & 13

Question 16

Which groups and types of elements form anions?

Answer 16

Nonmetals form anions - Group #15,16, & 17

Question 17

What are properties of an ionic substance?

Answer 17

Crystalline powders, high melting points, dissolve in water, conductive when dissolved in water, and brittle

Question 18

How does an ionic substance dissolve in water?

Answer 18

Charged sides of a water molecule attract to oppositely charged ions, pulling them out of their structure. The water forms hydration shells around the ions preventing the cation and anions from rejoining.

Question 19

Why is an ionic substance brittle but a metal is malleable?

Answer 19

Metals: Delocalized electrons can freely move so when their hit, they just move around, keeping the positive cations away from each other
Ions: Alternating cations and anions, but when hit the like-charged ions are pushed toward each other which causes them to repel each other, pulling away and breaking

Question 20

Why can ionic substances conduct electricity when dissolved in water?

Answer 20

Once dissolved, the charges (cations and anions) can move freely

Question 21

What are bonding pairs?

Answer 21

Covalent bonds between two atoms (shown in both Lewis Dot Structure and 3D models)

Question 22

What are nonbonding pairs?

Answer 22

Referred to as lone pair on the central atom (shown in Lewis Dot Structure but not in 3D models)

Question 23

2 Domains

Answer 23

2 bonding or lone pairs - Iner bond is 180 degrees (ex: H2, O2, CO2)

Question 24

3 Domains (3 bonding pairs)

Answer 24

Triganal Planar - 120 degrees (ex: BF3)

Question 25

4 Domains (Four bonding pairs)

Answer 25

Tetrahedral - 109.5 degrees (ex: CH4)

Question 26

3 Domains (2 bonding pairs, 1 lone pair)

Answer 26

Bent - Less than 120 degrees (ex: NOCL)

Question 27

4 Domains (3 bonding pairs, 1 lone pair)

Answer 27

Triganal Pyramid - Less than 107.5 degrees (ex: NH3)

Question 28

4 Domains (2 bonding pairs, 2 lone pairs)

Answer 28

Bent (er) - Less than 109.5 degrees (ex: H20)