Trends & Properties

One of the greatest strengths of the periodic table is its ability to reveal predictable patterns in the properties of elements. By understanding these periodic trends, you can anticipate an element's behaviour based solely on its position in the table — without needing to memorise the properties of every individual element.

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Key Periodic Trends

The major trends across the periodic table are governed by two opposing forces:

1. Effective nuclear charge (Z_eff) — the net positive charge experienced by valence electrons, after accounting for shielding by inner electrons
2. Electron shielding — the repulsion between inner electrons and valence electrons, which reduces the pull of the nucleus on the outermost electrons

As you move across a period (left to right), Z_eff increases because protons are added but electrons go into the same shell (minimal additional shielding). As you move down a group, new electron shells are added, increasing shielding and moving valence electrons further from the nucleus.

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1. Atomic Radius

Atomic radius is a measure of the size of an atom, typically defined as half the distance between the nuclei of two bonded atoms of the same element.