December | 2022 | Equivalent eXchange

The familiar periodic table of the elements may be overwhelming in its usual initial presentation. You may not have noticed that there are four blocks of elements in the table, and they even have names! All good atomists need to become facile with the chemical elements though, because they are indeed the building blocks of the universe!

The table is usually presented as a partial grid, consisting of 7 rows and 18 (or 32) columns, although there are alternate representations. But columns (C) are called groups (G) and rows (R) are called periods (P)!

Within the grid, elements are arranged in four blocks, with the following properties:

s-block: 2C x 7R = 14 (G1-2,18, P1-7) “sharp”
p-block: 6C x 6R = 36 (G13-18, P2-7) “principal”
d-block: 10C x 4R = 40 (G3-12, P4-7) “diffuse”
f-block: 14C x 2R = 28 (between G2 and G3, P6-7) “fundamental”

Note how columns (groups) increase (by four!) as rows (periods) decrease! Blocks are named after electron orbitals which are also named s, p, d, and f.

Thus there are currently 118 elements having a unique “atomic number” in the usual periodic table, with the rows or periods having the following number of elements:

P1: 2 (2s)
P2: 8 (2s, 6p)
P3: 8 (2s, 6p)
P4: 18 (2s, 6p, 10d)
P5: 18 (2s, 6p, 10d)
P6: 32 (2s, 6p, 10d, 14f)
P7: 32 (2s, 6p, 10d, 14f)

Note the number of groups increases as the period does. This is due to the properties of electrons and their shells. Familiar elements are scattered throughout the table, although they occur less and less as the atomic number increases. Elements can also occur as different isotopes due to having a differing number of electrons than usual, and so may have a positive or negative charge.

As an homage to the classical four elements, I’ve arranged the blocks as follows: the s-block has the reactive alkali and alkaline metals (fire), the p-block includes the noble gases (plus C, N, and O needed for life as we know it) (air), the d-block has the precious metals like gold, silver, and platinum (plus liquid at room temp mercury but not bromine) (water), and the f-block with the heaviest and often radioactive elements like uranium and plutonium (earth).