What you are actually practicing
The atomic number is an element's identity. It counts the protons in the nucleus, and it never changes — that is why the periodic table is arranged by it and why every element with the same number is the same element, wherever you find it.
The numbers also tell a story: 1 and 2 are the two lightest elements, 26 is iron, 79 is gold, 92 is uranium, and the gaps are the clues.
How the game works
You are shown an element and four numbers. Pick its atomic number. A wrong pick reveals it immediately.
Easy uses the light and familiar elements. Medium widens the set. Hard uses the full list, including the neighbours that are easy to confuse — gold at 79 and mercury at 80 are a classic pair.
The ones worth knowing
The first ten: hydrogen 1, helium 2, lithium 3, beryllium 4, boron 5, carbon 6, nitrogen 7, oxygen 8, fluorine 9, neon 10.
Everyday elements: sodium 11, magnesium 12, silicon 14, sulfur 16, chlorine 17, argon 18, potassium 19, calcium 20.
The heavy famous ones: iron 26, copper 29, zinc 30, silver 47, gold 79, mercury 80, lead 82, uranium 92.
Strategies that actually raise your score
Anchor on a known pair. The periodic table's neighbours are memorable: gold 79 next to mercury 80 next to lead 82. Learn one pair and you have three numbers.
Use the gap. Atomic numbers rise in order of discovery and stability, so a jump to 92 means a heavy synthetic element, not something common.
Reject the near neighbours. The options usually include the correct number and its neighbours. If two options are close together, one of them is the element above or below in the table.
Remember the count, not the list. There are only 94 elements, and the first twenty cover almost everything you meet in daily life.