Where does the dot go on the H ? On the side or above? I do know that there is only one because of where it is located on the periodic table.
Also with Ca^2+
wouldn't the charge cancel? so what would you write?
H has one electron in the first orbital ring. Unlike the elements further down than H and He, those two elements can only fit 2 electrons in that first shell.
So an H atom would have one dot anywhere in the shell. When H forms a Covalent bond there are two dots in that shell, one of those belonging to the other element. Then that shell is full and the compound is happy.
Ca+2 is missing two electrons in its outer shell The neutral Ca atom has 20 electrons
2 fill the first shell
8 more in the second so 10 so far
8 more in the third so 18 so far
That puts 2 in the outer shell which is happier with 0 or 8
If it loses 2 electrons, it then has eight in the third shell so full and happy, but now there are two more protons than electrons so the charge is +2
see: https://www.khanacademy.org/science/chemistry/chemical-bonds/copy-of-dot-structures/v/drawing-dot-structuresposted by Damon
To add to Damon's excellent answer another way to do this is this way and this avoids filling in all those shells with dots. Write the symbol for the element first, then add dots FOR THE OUTER SHELL.
H. would be hydrogen
Ca: would be calcium
Ca^2+ or Ca^++ would be the calcium ion. You will learn more about this when you study Lewis structures, also called Lewis electron dot structures.posted by DrBob222