You can find a periodic table online or in a chemistry book. In tests, normally, a periodic table will be provided.
Using the group (columns) or period (rows) can make the element easier to locate on the table. You can also search the table for the symbol of the element if you don’t know any other properties.
For example, boron (B) has an atomic number of 5, therefore it has 5 protons.
For example, boron (B) has an atomic number of 5, therefore it has 5 protons and 5 electrons. However, if the element includes a negative or positive ion, then the protons and electrons will not be the same. You will have to calculate them. The ion number will appear as a small superscript after the element.
Make sure that you round the atomic mass to the nearest whole number. For example, the atomic mass of boron is 10. 811, but you can just round the atomic mass up to 11.
For our boron example, 11 (atomic mass) – 5 (atomic number) = 6 neutrons
Because an electron has a negative charge, when you remove electrons, the ion becomes positive. When you add more electrons, the ion becomes negative. For example, N3- has a -3 charge while Ca2+ has a +2 charge. Keep in mind that you do not have to do this calculation if there is no superscripted ion number following the element.
For example, Ca2+ has a +2 charge so it has lost 2 electrons from the neutral state. Calcium’s atomic number is 20, therefore the ion has 18 electrons.
For example, N3- has a -3 charge; therefore, it has gained 3 electrons compared to the neutral state. Nitrogen’s atomic number is 7, therefore this ion has 10 electrons.
