1.19: Understand How to Deduce the Electronic Configuration of the First 20 Elements from their Positions in the Periodic Table

ELECTRONIC CONFIGURATION: Arrangement of Electrons into shells for an Atom

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• Electrons always occupy shells that are closest to the Nucleus first
• When a shell becomes full, Electrons will fill the next shell

ELECTRONIC CONFIGURATION OF FIRST 20 ELEMENTS:

ELEMENT	NUMBER OF ELECTRONS	ELECTRONIC CONFIGURATION
HYDROGEN	1	1
HELIUM	2	2
LITHIUM	3	2 . 1
BERYLLIUM	4	2 . 2
BORON	5	2 . 3
CARBON	6	2 . 4
NITROGEN	7	2 . 5
OXYGEN	8	2 . 6
FLUORINE	9	2 . 7
NEON	10	2 . 8
SODIUM	11	2 . 8 . 1
MAGNESIUM	12	2 . 8 . 2
ALUMINIUM	13	2 . 8 . 3
SILICON	14	2 . 8 . 4
PHOSPHORUS	15	2 . 8 . 5
SULFUR	16	2 . 8 . 6
CHLORINE	17	2 . 8, . 7
ARGON	18	2 . 8 . 8
POTASSIUM	19	2 . 8 . 8 . 1
CALCIUM	20	2 . 8 . 8 . 2