Question

two questions answer faast❤❤

1. How and why does the valency of an element vary as you go:
a. from left to right along a period.
b. down the group.

2. Account for the following
a. All the elements of the same group have similar properties.
b. The noble gases were discovered very late.​

Answer 1

Answer :

1.

• a) Valency in a particular period from left to right first increases as positive valency and then decreases as negative valency because from left to right the number of valence electrons increases by one unit and the tendency to gain electron increases after group 14 elements.

• b) Down the group valency remains the same because the valence electrons of each element remains the same in a particular group. Only the number of shells increase down a group.

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2.

• a) All the elements of the same group have similar properties because the elements of the same group have the same number of valence electrons and hence same valency. Hence, they have similar chemical properties as the valency of an element decides its chemical reactivity.

• b) The noble gases were discovered late because they were inert (chemically inactive) and present in extremely low concentrations in the atmosphere. Hence, they were very difficult to be found.