Q30 of 65 Page 18

The electronic configurations of three elements X, Y and Z are X — 2, 8; Y — 2, 8, 7 and Z — 2, 8, 2. Which of the following is correct?

Atomic number of X is 10, so this must be Ne (Neon), a noble or inert gas. This gas has octate configuration.


Atomic number of Y is 2 + 8 + 7 = 17, so this must be chlorine (Cl). Chlorine is a non–metal. Non-metals have 5 to 7 electrons in their valence shell.


Atomic number of Z is 2 + 8 + 2 = 12, so this must be Magnesium (Mg). Magnesium is a metal. Metals have 1 or 2 electrons in their valence shell.

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