How many protons and electrons are in each?

Question

Please explain how to find the answer instead of just providing it. Thank you.

1. I (-)

2. Ca (2+)

3. Na (+)

PS. The #'s and signs in parentheses are supposed to be in superscript.

Answer 1

1. Iodine's atomic number is 53. This means it has 53 protons. To be negatively charged (-1), it must have an extra electron. So there are 53 protons and 54 electrons.

2. Calcium 2+ has 20 protons. It must have two electrons less than its number of protons. It has 20 protons and 18 electrons.

3. Sodium (1+) has 11 protons. But, it's lacking a proton. So there are 11 protons and 10 electrons.

Answer 2

1. I (-) has 53 protons and 54 electrons

2. Ca(2+) has 20 protons and 18 electrons

3. Na (+) has 11 protons and 10 electrons

Answer 3

The number of protons is the same as the atomic number (even if it is an ion). For a neutral (uncharged) atom, the number of electrons will be equal to the number of protons, if there is a charge, you need to adjust the number of electrons to correspond. For  Ca+2, look up the atomic number which is 20 [don't use atomic weight by mistake !] since it is a +2 ion, you take away 2 electrons to find the appropriate number. 20 - 2 = 18 electrons. For negatively charged ions, you need to add electrons, otherwise it is the same.