What isotope has 12 protons, 13 neutrons and 12 electrons?

Magnesium

Magnesium, in its elemental form, has 12 protons and 12 electrons. The neutrons are a different matter. Magesium's average atomic mass is 24.305 atomic mass units, but no magnesium atom has exactly this mass.

Hope this helps Stay safe and have a Merry Christmas :D

alkaline metals are lithium, sodium, rubidium, potassium, cesium and francium.

alkali metals have electronegativity from 0.7 to 1, lowest in periodic table of elements, which means that alkali metals (i group in periodic table) has positive oxidation number in compounds.

electronegativity is a chemical property that describes the tendency of an atom to attract a shared pair of electrons towards itself.

alkaline metals (far left in main group) have lowest ionizations energy and easy remove valence electrons,

for example, potassium is the alkali metal and has a single valence electron in the outer electron shell.

electron configuration of potassium is: ₁₉k 1s²2s²2p⁶3s²3p⁶4s¹.

they can not exist alone in nature, because they are very reactive.