What element has the symbol 'Mg'?

The story behind the answer

‘Mg’ is the symbol for magnesium, element 12. The other options have different symbols: mercury is Hg (from hydrargyrum), manganese is Mn, and molybdenum is Mo. So only magnesium matches Mg.

Magnesium is a lightweight, silvery alkaline earth metal used in “mag wheels,” aircraft alloys, and bright-white flares and fireworks. Biologically, it’s essential for enzymes and sits at the heart of chlorophyll—think “Mighty Green” to remember Mg. Another hook: “Mag” sounds like “magnesium,” while the odd ones out keep extra letters—Hg, Mn, Mo—so Mg is the clean, direct match for magnesium.