Calcium (Ca) is element number 20 on the periodic table. It is an alkaline earth metal (Group 2, Period 4) and one of the most biologically important elements — essential for bones and teeth.
Atomic Number: 20.
Full Configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s².
Shell Configuration: 2, 8, 8, 2.
Shorthand: [Ar] 4s².
Ca²⁺ Ion: [Ar] — noble gas configuration.
Valency: 2.
Atomic Number of Ca: 20
Full Electron Configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s²
Shell-wise (Bohr model): 2, 8, 8, 2
Shorthand (Noble gas notation): [Ar] 4s²
This means Calcium has the same inner configuration as Argon ([Ar]) plus 2 electrons in the 4s orbital.
When Calcium forms an ion (Ca²⁺), it loses its 2 outermost electrons (4s²):
Ca²⁺ Configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ = [Ar] (Noble gas configuration)
This is why Calcium readily loses 2 electrons — doing so gives it the stable configuration of Argon.
Calcium's electron configuration is 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² or in shells: 2, 8, 8, 2.
Ca²⁺ loses 2 electrons (4s²), giving it the configuration 1s² 2s² 2p⁶ 3s² 3p⁶ — same as Argon (noble gas).
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