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Periodic Table Period




The number of Electron Shell s an atom has determines what period it belongs to. Each shell is divided into different subshells, which as Atomic Number increases are filled in roughly this order:

1s
2s 2p
3s 3p
4s 3d 4p
5s 4d 5p
6s 4f 5d 6p
7s 5f 6d 7p
8s 5g 6f 7d 8p
...

Hence the structure of the periodic table. Since the outermost electrons determine chemical properties, those tend to be similar within Periodic Table Group s.

Elements adjacent to one another within a group have similar physical properties, despite their significant differences in mass. Elements adjacent to one another within a period have similar mass but different properties.

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