The diagram below shows that the periodic table is divided into different blocks.

A periodic table is shown. The main table consists of seven rows; two additional rows are shown below. In each block, the first column is labeled and the remaining columns are empty. The s-block is shaded in yellow and comprises the first two columns, plus one cell at the far side of the table. The first column has seven rows with entries 1 s, 2 s, 3 s, 4 s, 5 s, 6 s, and 7 s. A lone cell labeled 1 s appears at the top far right corner, aligned with the 1 s cell in the first column. The d-block is shaded in blue and contains 10 columns and 3 or 4 rows. The first column is directly to the right of the s-block. The first entry in the first d-block column aligns with the 4 s block, and is labeled 3d; further entries in that column are 4 d, 5 d, and 6 d. The first three columns in the block are four entries long; the remaining columns are three entries long, losing the bottom entry. The p-block is shaded in orange, and has 6 columns and 5 rows. The top row aligns with the 2 s block; entrie

Elements that have complete valence electron shells are mostly found in the
s block.
d block.
p block.
f block.