Introduction

Electron configurations are a list of the subshells on an atom that are occupied.
 
Each subshell has a shell number and a letter designation (1s for example).
The number of electrons is given by a superscript. For H the electron configuration is 1s1.

The maximum number of electrons per subshell (s subshell - 2, p subshell - 6, d subshell - 10) corresponds to the number of groups in the blocks in the periodic table.

Thus the periodic table can be used as a guide for constructing the electron configuration of an element.
 
1 2
  1H 2He
3 Li 4 Be   5 B 6 C 7 N 8 O 9 F 10 Ne
11 Na 12 Mg 13 Al 14 Si 15 P 16 S 17 Cl 18 Ar
19 K 20 Ca 21 Sc 22 Ti 23 V 24 Cr 25 Mn 26 Fe 27 Co 28 Ni 29 Cu 30 Zn 31 Ga 32 Ge 33 As 34 Se 35 Br 36 Kr
37 Rb 38 Sr 39 Y 40 Zr 41 Nb 42 Mo 43 Tc 44 Ru 45 Rh 46 Pd 47 Ag 48 Cd 49 In 50 Sn 51 Sb 52 Te 53 I 54 Xe
55 Cs 56 Ba 71 Lu 72 Hf 73 Ta 74 W 75 Re 76 Os 77 Ir 78 Pt 79 Au 80 Hg 81 Tl 82 Pb 83 Bi 84 Po 85 At 86 Rn
s-block
2 		 d-block
10 groups		  p-block
6 groups
Dr Sheila Woodgate
© The University of Auckland 2002