Question

In a periodic table : (a) How does the tendency to gain electrons change in a period ? (b) How does the trndency to form basic oxide change down a group ? (c) How does the valency of element vary on going down the group ?

Answer 1

Gain electron changes from left to right in periodic table.
From top to bottom.
Valency vary from electron 1to 4 (loss) 5to 7(gain)

Answer 2

a)Tendency to gain electrons increases and we go
from left to rigth in a period because the
effective nuclear charge increases and the
atomic radius decreases. So the protons hold the
elcetrons more tightly thus the losing of
elcetrons becomes difficult.
b) the tendency to form basic oxides increases
down the group as the mattalic charachter
increases and as we know metal form basic
oxides therefore the tendency to form basic
oxides alos increases
c) It should be noted that, during the classification
of elements,all the elements with similar valance
electrons are placed in same group in a periodic
table.
Hence, when we move down the group, the
valence shell changes, because the period no.
changes, but the valency remains the same. For
ex;
in group 1; -. in Li(Lithium)- valence shell is 2s1
while the second element Na(sodium) has
valence shell 3s1
But, in all the elements the valency remains the
same as 1 because they have only one electron
in their outermost s-orbital.