Question

How many valence electrons are present in `40*g` mass of calcium metal?

Answer 1

There are approx. `2xxN_A` valence electrons, where `N_A-="Avogadro's number"`..........

Explanation:

Each calcium atom has 2 valence electrons, and calcium commonly forms a `Ca^(2+)` ion..........

Now the molar mass of calcium is `40.1*g*mol^-1`, and thus a 40 gram quantity of calcium metal CONTAINS `6.022xx10^23` individual calcium atoms. Note that this is the principle of chemical equivalence. If you gots the mass of something, you know the number of fundamental particles of stuff that make up that something.

And so we gots `12.022xx10^23` individual electrons.........