Fig 6The periodic table118 elementscoloured by last orbital filled
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The table is the shell-filling order laid out in rows. Each row starts a new shell, and each column holds elements with the same arrangement of outer electrons, which is why the elements in a column behave alike. The blocks name the orbital being filled. Metals, on the left and in the middle, have few outer electrons and give them up easily, while non-metals, at the top right, are close to a full shell and take electrons in.