hydrogen

1

H

1.008

helium

2

He

4.003

lithium

3

Li

6.94

Boron

5

B

10.81

oxygen

8

O

15.999

aluminium

1

Al

1.008

scandium

21

Sc

44.96

Selenium

21

Se

78.97

Caesium

55

Cs

132.9

actinium

89

Ac

227

uranium

92

U

238

plutonium

94

Pu

244.1

Lightest

Heaviest

alkali
metal

alkali
earth metal

p-transition
metal

transition
metal

metaloids

lathinides

actinides

diatomic
nonmetal

noble
gas

other
nonmetal