Unit 4- atoms combining

Question 1

How many kinds of atoms do an element contain

Answer 1

one

Question 2

What is a compound

Answer 2

A substance in which two or more elements are chemically combined

Question 3

Signs of a chemical change

Answer 3

One or more new chemical substances are formed, energy is taken in or given out, usually difficult to reverse

Question 4

Difference between chemical and physical change

Answer 4

In chemical change, there is new chemical substance formed but not in a physical change

Question 5

What are ions

Answer 5

Charged particle. It’s charged because it has an unequal number of protons and electrons.

Question 6

Why do atoms form bonds

Answer 6

Atoms bond with each other in order to gain a stable outer shell

Question 7

What is an ionic bond

Answer 7

The bond that forms between ions of opposite charge

Question 8

How is an ionic bond formed

Answer 8

The metal reacts with a non-metal to form an ionic compound. The metal atoms lose electrons. The non-metal atoms gain them. The ions form a lattice of alternating positive and negative ions.

Question 9

What is an overall charge for a compound

Answer 9

0

Question 10

Charge of hydroxide ion

Answer 10

1-

Question 11

Charge of nitrate ion

Answer 11

1-

Question 12

charge of sulfate ion

Answer 12

2-

Question 13

charge of carbonate ion

Answer 13

2-

Question 14

charge of ammonium ion

Answer 14

1+

Question 15

What is a covalent bond

Answer 15

the chemical bond formed when two atoms share electrons

Question 16

What is a bond between chlorine molecules

Answer 16

single covalent bond

Question 17

What is a bond between oxygen molecules

Answer 17

double (covalent) bond

Question 18

What is a molecule

Answer 18

Group of atoms held together by covalent bonds

Question 19

Why are forces between particles stronger between ionic compound than covalent compound

Answer 19

In Ionic compound, particles are chared so forces between them are strong, but in a covalent compound is particles are not charged.

Question 20

Properties of an ionic compound

Answer 20

High melting and boiling point, usually soluble in water, conduct electricity when melted or dissolved in water

Question 21

Properties of a covalent compound

Answer 21

Low melting and boiling point, tend to be insoluble in water, do not conduct electricity

Question 22

Why does diamond has a high melting point

Answer 22

Each atom is held in place by four strong covalent bonds

Question 23

Why can’t diamond conduct electricity

Answer 23

There are no ions or free electrons

Question 24

What type of structure are diamonds and silicon (iv) oxide

Answer 24

Giant covalent structure ( tetrahedral shape)

Question 25

What are allotropes

Answer 25

Different forms of the same element

Question 26

Properties of graphite

Answer 26

Soft because sheets can slide over each other easily. Good conductor of heat and electricity because there are free electrons

Question 27

What is a metallic bond

Answer 27

The attraction between metal ions and free electrons

Question 28

Why do metals usually have a high melting point

Answer 28

It takes a lot of heat energy to break up the lattice, with its strong metallic bonds.

Question 29

Why metals are malleable and ductile

Answer 29

The layers can slide over each other.

Question 30

Why metals are good conductors of heat

Answer 30

There are free electrons that take in heat energy which makes them move faster, they quickly transfer heat through the metal structure.

Question 31

Why metals are good conductors of electricity

Answer 31

Free electrons can move through the lattice carrying charge when a voltage is applied across the metal.