3.4 How electrons are arranged

Question 1

Electron shells

Answer 1

Electrons are arranged in shells around the nucleus.

The first shell, closest to the nucleus, is the lowest energy level.

The further a shell is from the nucleus, the higher the energy level.

Question 2

How many electrons can the first shell hold?

Answer 2

The first shell can only hold 2 electrons. It fills first.

Question 3

How many electrons can the second shell hold?

Answer 3

The second shell holds 8 electrons.

Question 4

How many electrons can the third and fourth shell hold?

Answer 4

The third shell can hold 18 electrons but it fills up to 8. The next 2 go into the fourth shell. Then the rest of the third shell fills.

Question 5

Hydrogen electron configuration

Answer 5

1

Question 6

Helium electron configuration

Period 1 Group VIII

Answer 6

2

Question 7

Lithium electron configuration

Answer 7

2+1

Question 8

Beryllium electron configuration

Answer 8

2+2

Question 9

Boron electron configuration

Answer 9

2+3

Question 10

Carbon electron configuration

Answer 10

2+4

Question 11

Nitrogen electron configuration

Answer 11

2+5

Question 12

Oxygen electron configuration

Answer 12

2+6

Question 13

Fluorine electron configuration

Answer 13

2+7

Question 14

Neon electron configuration

Answer 14

2+8

Question 15

Sodium electron configuration

Answer 15

2+8+1

Question 16

Magnesium electron configuration

Answer 16

2+8+2

Question 17

Aluminium electron configuration

Answer 17

2+8+3

Question 18

Silicon electron configuration

Answer 18

2+8+4

Question 19

Phosphorus electron configuration

Answer 19

2+8+5

Question 20

Sulfur electron configuration

Answer 20

2+8+6

Question 21

Chlorine electron configuration

Answer 21

2+8+7

Question 22

Argon electron configuration

Answer 22

2+8+8

Question 23

Potassium electron configuration

Answer 23

2+8+8+1

Question 24

Calcium electron configuration

Answer 24

2+8+8+2

Question 25

What does the period number tell you?

Answer 25

The period number tells you how many shells there are.

Question 26

What are valency electrons?

Answer 26

Outer shell electrons

Question 27

What does the group number tell you?

Answer 27

The group number is the same as the number of valency electrons.

Question 28

Group VIII

Answer 28

Group VIII elements are unreactive as they all have 8 or 2 outer shell electrons.

Question 29

Reactions of isotopes

Answer 29

All isotopes of an element have the same number of valency electrons, so their chemical reactions are the same.

Question 30

Terms for how the electrons are arranged in shells.

Answer 30

Electron arrangement
Electronic configuration
Electron distribution
Electronic structure