Is calcium an cation or anion?

As the elemental metal, calcium is neither a cation nor an anion. Its elemental symbol is 'Ca(s)' . 's' indicating that it is solid.

However, like sodium , calcium readily ionises ( loses) 2(two) electrons. Symbolically it is now 'Ca^(2+) ' . It is an ION. Because it is a positive(+) ion , it is known as a 'CATION'.

Compare to chlorine, it has electron affinity, and symbolically it is ' Cl^(-) ' . It is also an ION. But because it is a negative (-) ion , it is known as an ANION.

So remember. any atom that loses or gains electrons, is no longer an atom, but an ION.

If the ion is positively(+) charged, then it is a CATION , and if the ion is negatively(-) charged , then it is an ANION.