A neutral magnesium atom in its ground state has zero unpaired electrons. All 12 of its electrons are arranged in fully occupied orbitals, with every electron paired with a partner spinning in the opposite direction.
Magnesium’s Electron Configuration
Magnesium has 12 electrons, and they fill orbitals in a predictable order: 1s² 2s² 2p⁶ 3s². Each superscript number tells you how many electrons sit in that orbital or set of orbitals. The 1s orbital holds 2 electrons (its maximum), the 2s orbital holds 2, the three 2p orbitals hold a combined 6 (also their maximum), and the outermost 3s orbital holds 2.
Every one of these orbitals is completely full. Because each orbital can hold exactly two electrons, and two electrons in the same orbital must spin in opposite directions, every electron in magnesium has a partner. No electron is left alone, which is what “unpaired” would mean.
Why Pairing Matters
Unpaired electrons give an atom a net magnetic field. When two electrons share an orbital, their opposite spins cancel each other’s magnetism out. An atom with no unpaired electrons is called diamagnetic: it has no intrinsic magnetic pull and is actually weakly repelled by an external magnet.
Interestingly, bulk magnesium metal is sometimes classified as weakly paramagnetic (slightly attracted to magnets). This comes not from unpaired electrons in individual atoms but from the way electrons behave when billions of magnesium atoms pool their outermost electrons into a shared metallic “sea.” The isolated atom itself, though, is diamagnetic because every electron is paired.
What About the Mg²⁺ Ion?
When magnesium forms its common ion, Mg²⁺, it loses both of its 3s electrons. The remaining configuration is 1s² 2s² 2p⁶, identical to a neon atom. Every orbital is still fully occupied, so Mg²⁺ also has zero unpaired electrons. This is one reason magnesium so readily gives up exactly two electrons: the resulting ion has a completely filled, very stable set of orbitals.
Magnesium in an Excited State
The answer changes if magnesium absorbs energy. In its first excited state, one of the two 3s electrons jumps up to a 3p orbital, giving a configuration of 1s² 2s² 2p⁶ 3s¹ 3p¹. Now there are two unpaired electrons, one in the 3s and one in the 3p, each sitting alone in its orbital. This excited state requires about 62 kcal/mol of energy to reach and is not the normal condition of the atom, which is why the standard answer remains zero.
All Group 2 Elements Follow the Same Pattern
Magnesium belongs to Group 2 of the periodic table, the alkaline earth metals. Every element in this group (beryllium, magnesium, calcium, strontium, barium, and radium) has a ground-state configuration that ends in a filled ns² orbital. That means all of them share the same answer: zero unpaired electrons in the ground state. Their excited-state behavior differs, with heavier members like calcium and barium favoring d orbitals over p orbitals, but in the resting state they all have every electron neatly paired.