Question

2.in an element there are 29 electrons. then
1)what will be the outer most shell of the element?
2)write the valency of the element?
3)mention its atomic number?
4)how can we find the valency of the element ?

Answer 1

There are 29 electrons. Therefore, its electronic configuration is- (2,8,18,1)
(1) The outermost shell is the N shell with 1 electron
(2) The valency is 1 (as valence/outer electron is 1)
(3) Atomic no.= no. of protons= no. of electrons= 29
(4) This is certainly a metal (Copper) as the range of electrons is between 1-3 (1 here), so its valency is simply the no. of valence electrons in it, i.e. 1+)
If there are 1,2 or 3 electrons in the outermost shell, then the valency is the no. of outermost electrons
If there are 5,6,7 electrons, the valency can be obtained by subtracting the no from 8 , eg: if there are 6 electrons in the outermost shell, then valency=8-6=2
If there are already 8 electrons in the outermost shell, then valency is 0, that is those elements don't react, eg= Helium, argon
If there are 4 electrons, valency is 4 (8-4=4), so the elements start forming bonds.
Other elements either gain (valency 1,2,3) or lose electrons (valency 5,6,7).

Answer 2

1) 2,8,18,1
So 1 electrons in outermost shell.

2) valency = 1 as it can lose one electron to form a compound.

3) Atomic number = number of electrons = 29

4)To find the valency of the atom first you need to know the number of electrons in outermost shell(n)
If n > 4 then valency = 8-n
If n< or = 4 then valency = n