Activity 1.5

1	Write the electronic configuration of elements from atomic number 11 to 18.

Ans:

Element Symbol Atomic Number Shell Configuration Electronic Configuration K (2) L (8) M (18) N (32) Sodium Na 11 2 8 1 2, 8, 1 Magnesium Mg 12 2 8 2 2, 8, 2 Aluminium Al 13 2 8 3 2, 8, 3 Silicon Si 14 2 8 4 2, 8, 4 Phosphorus P 15 2 8 5 2, 8, 5 Sulphur S 16 2 8 6 2, 8, 6 Chlorine Cl 17 2 8 7 2, 8, 7 Argon Ar 18 2 8 8 2, 8, 8

2	What similarities do you find in their electronic configuration?

Ans:	Elements from atomic number 11 to 18 have the same number of electrons in their first two shells.

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3	How many valence electrons are present in sodium, aluminum and chlorine?

Ans:	Element Sodium Aluminium Chlorine Valence Electrons 1 3 7

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4	Write the electronic configuration of (i) Mg and Ca and (ii) F and Cl.

Ans:	Element Mg Ca F Cl Electronic Configuration 2, 8, 2 2, 8, 8, 2 2, 7 2, 8, 7

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5	Do these elements contain same number of valence electrons?

Ans:	Yes, magnesium and calcium contain the same number of valence electrons. Also, Fluorine and chlorine contain the same number of valence electrons. (Valence electrons: The number of electrons in the outermost orbit)

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6	Write the electronic configuration of B, O, Na, Al, S and K.

Ans:	Element Electronic Configuration Boron (B) 2, 3 Oxygen (O) 2, 6 Sodium (Na) 2, 8, 1 Aluminium (Al) 2, 8, 3 Sulphur (S) 2, 8, 6 Potassium (K) 2, 8, 8, 1