Helium

(a)  

Lithium

(a)  

Be

(a)  

Boron

(a)  

Carbon

(a)  

N

(a)  

O

(a)  

Fluorine

(a)  

Ne

(a)  

Sodium

(a)  

Mg

(a)  

Al

(a)  

Silicon

(a)  

P

(a)  

S

(a)  

Chlorine

(a)  

Argon

(a)  

K

(a)  

Ca

(a)