1 - 4 The periodic table
● ***Arranged in order of atomic number
● Vertical columns: groups, horizontal rows: periods
● ***Electron energy shells/levels (maximum room for number of electrons)
○ First level: 2
○ Second level: 8
○ Third level: 8
○ Fourth level: 18***
Electron configuration***
● E.g.: chlorine atom
● 17 - 2 (first shell) - 8 (second shell) = 7 (maximum number of electrons that can fill
the shell)
● Electron configuration of chlorine: 2, 8, 7
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● ***Arranged in order of atomic number
● Vertical columns: groups, horizontal rows: periods
● ***Electron energy shells/levels (maximum room for number of electrons)
○ First level: 2
○ Second level: 8
○ Third level: 8
○ Fourth level: 18***
Electron configuration***
● E.g.: chlorine atom
● 17 - 2 (first shell) - 8 (second shell) = 7 (maximum number of electrons that can fill
the shell)
● Electron configuration of chlorine: 2, 8, 7
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