01
Find a periodic table of elements. This is a color-coded table made up of many different squares that lists all of the chemical elements known to humankind. The periodic table reveals lots of information about the elements — we'll use some of this information to determine the number of valence electrons in the atom we're investigating. You can usually find these inside the cover of chemistry textbooks. There is also an excellent interactive table available online.
2
Label each column on the periodic table of elements from 1 to 18.Generally, on a periodic table, all of the elements in a single vertical column will have the same number of valence electrons. If your periodic table doesn't already have each column numbered, give each a number starting with 1 for the far left end and 18 for the far right end. In scientific terms, these columns are called the element "groups."
For example, if we were working with a periodic table where the groups aren't numbered, we would write a 1 above Hydrogen (H), a 2 above Beryllium (Be), and so on until writing an 18 above Helium (He).
3
Find your element on the table. Now, locate the element that you want to find the valence electrons for on the table. You can do this with its chemical symbol (the letters in each box), its atomic number (the number in the top left of each box), or any of the other pieces of information available to you on the table.
- For example purposes, let's find the valence electrons for a very common element: carbon (C). This element has an atomic number of 6. It is located at the top of group 14. In the next step, we'll find its valence electrons.
- In this subsection, we're going to be ignoring the Transitional metals, which are the elements in the rectangle-shaped block made by Groups 3 to 12. These elements are a little different from the rest, so the steps in this subsection won't work on them. See how to deal with these in the subsection below.
- Group 2: 2 valence electrons
- Group 13: 3 valence electrons
- Group 14: 4 valence electrons
- Group 15: 5 valence electrons
- Group 16: 6 valence electrons
- Group 17: 7 valence electrons
- Group 18: 8 valence electrons (except for helium, which has 2)
- In our example, since carbon is in group 14, we can say that one atom of carbon has four valence electrons.
