(a) Since element X burns in the presence of oxygen to form a basic oxide this means that it is metal and it’s atomic number is 20 so it is calcium (Ca). It’s electronic configuration is Ca20 = 2, 8, 8, 2 (b) We know that group number is equal to valence shell electrons and period is equal to number of shells contain by the element. Element X has 2 valence shell electrons and 4 shells so its group number is 2 and period is 4th. (c) CaO + H2O → Ca(OH)2 Note- Balancing of chemical equation- (i) Here one Ca atom is in left side and one Ca atom is in right side. So Ca atoms are equal. (ii) And we shall check that other atoms are equal or not. If the other atoms are equal to both side then the equation is balanced. If the other atoms are not equal then we shall equal them. Now Ca atoms are equal, H atoms are equal and O atoms are also equal on both sides. So the chemical equation is balanced.

Q. 194.7( 3 Votes )

An element &lsquo

Class 10th

Answer :

(a) Since element X burns in the presence of oxygen to form a basic oxide this means that it is metal and it’s atomic number is 20 so it is calcium (Ca). It’s electronic configuration is

Ca₂₀ = 2, 8, 8, 2

(b) We know that group number is equal to valence shell electrons and period is equal to number of shells contain by the element. Element X has 2 valence shell electrons and 4 shells so its group number is 2 and period is 4^th.

Note- Balancing of chemical equation-

(i) Here one Ca atom is in left side and one Ca atom is in right side. So Ca atoms are equal.

(ii) And we shall check that other atoms are equal or not. If the other atoms are equal to both side then the equation is balanced. If the other atoms are not equal then we shall equal them.

Now Ca atoms are equal, H atoms are equal and O atoms are also equal on both sides. So the chemical equation is balanced.

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