Transition elements are found in the middle of the periodic table. These elements are all metals, and the ten transition metal groups (3-12) are shown in green below.

1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18
1 H																2 He
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

As transition metals in the same row have similar properties (atomic size, ionization energy for example), chemists speak of transition series. The first transition series is the elements at the top of Groups 3-12. These will be the focus of the module which follows.