Q5 of 56 Page 1

Why do all the elements of the (a) same group have similar properties, (b) same period have different properties?

(a) The elements present in same group have same number of valence electrons due to which they have similar properties.

(b) The elements present in same period have different number of valence electrons due to which they have different properties.


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Write the name and formula of a molecule made up of three atoms of oxygen.

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What is the colour of the clear sky during day-time? Give reason for it.

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An element E has following electronic configuration:

K L M


2 8 6


(a) To which group of the periodic table does element E belong?


(b) To which period of the periodic table does element E belong?


(c) State the number of valence electrons present in element E.


(d) State the valency of the element E.

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