alkali
metal
hydrogen
1
1.008
helium
2
4.003
lithium
3
6.94
Boron
5
10.81
oxygen
8
15.999
aluminium
1
1.008
scandium
21
44.96
Selenium
21
78.97
Caesium
55
132.9
actinium
89
227
uranium
92
238
plutonium
94
244.1
Lightest
Heaviest
alkali
metal
alkali
earth metal
p-transition
metal
transition
metal
metaloids
lathinides
actinides
diatomic
nonmetal
noble
gas
other
nonmetal