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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 here.
The valence Electron are the electrons in last electron shell is the valence electrons.
Hope this helps
Hope this helps