If I have a +2 oxidation number do I give up or accept electrons?​

Give up 2 electrons.

Explanation:

Is this ever a good question!!!

Electrons have a minus charge

Protons have a plus charge.

You need to understand it thoroughly.  I used to explain it this way.

Suppose the protons and electrons are playing a game and the electrons commit a foul that leaves them with 2 men short.

That means there are 2 unguarded plus's around. The result is that the minuses have lost two men who are in the sin bin. (I watch a lot of hockey).

So a +2 means that the electrons have lost two of their players to penalties.

Put in the vocabulary of your question, you give up 2 electrons.

there are two significant figures.

ca has a crystalline lattice with positive ions (since it is a metal, metals are positively charged) and electrons flow freely in its structure since the ca atoms have a large nuclear radius so the electrons are not tightly held, therefore the electrons can flow freely since they are not being highly attracted by the nucleus. moreover, one of the properties of metals are that they are conductors of electricity, thus proving ca is the element.