Calculating Mass Number

The Helium (He) atom in Group 18 has 2 protons and the mass number is 4. How many neutrons are in the Helium (He) atom?

• 1

• 2

• 3

• 4

The Boron (B) atom in Group 13 has 5 protons and the mass number is 11. How many neutrons are in the Boron (B) atom?

• 5

• 6

• 7

• 8

The Chromium (Cr) atom in Group 6 has 24 protons and the mass number is 52. How many neutrons are in the Chromium (Cr) atom?

• 26

• 27

• 28

• 29

The mass number of the Calcium (Ca) atom in Group 2 is 40 and the number of protons is 20. How many neutrons are in the Calcium (Ca) atom?

• 20

• 30

• 40

• 50

The mass number of the Potassium (K) atom in Group 1 is 39 and the number of protons is 19. How many neutrons are in the Potassium (K) atom?

• 10

• 20

• 30

• 40

The Magnesium (Mg) atom in Group 2 has 12 protons and 12 neutrons. What is the mass number of Magnesium (Mg) atom?

• 24

• 25

• 26

• 27

The Oxygen (O) atom in Group 16 has 8 protons and 8 neutrons. What is the mass number of Magnesium (Mg) atom?

• 14

• 15

• 16

• 17

The Aluminum (Al) atom in Group 13 has 13 protons and 13 neutrons. What is the mass number of Aluminum (Al) atom?

• 25

• 26

• 27

• 28

The Iron (Fe) atom in Group 8 has 26 protons and 30 neutrons. What is the mass number of Iron (Fe) atom?

• 26

• 36

• 46

• 56

The Fluorine (F) atom in Group 17 has 9 protons and 10 neutrons. What is the mass number of Magnesium (Mg) atom?

• 19

• 20

• 21

• 22