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