Question

Na and Cl are in the same period.
They are expected to have same number of ---------
(a)Valence electrons (b)shells (c)protons
(d)electrons.

Pls ans quickly!!

Answer 1

Na and Cl are in same period. They are expected to have same number of _______.

Na (sodium) belongs to a 1st group and 3rd period of a periodic table.

As, it's belongs to a 1st group means, in it's outer most shell there is a single electron.

$\sf{Electronic \:configuration \:of\:Na\:=\:1s^22s^22p^63s^1}$

Similarly,

Cl (chlorine) belongs to 17th group and 3rd period of a periodic table.

$\sf{Electronic \:configuration \:of\:Cl\:=\:1s^22s^22p^63s^23p^5}$

From above we find that both Na and Cl belongs to same period number i.e. 3 (as said in question too)

So, along the period :

• Number of shells remains constant (same). Since, both Na and Cl belongs to same period i.e 3 then their shell number is also same.

• Atomic size of an atom decreases as we move from left to right along a period. (because of large positive charge, electrons come more closer to the nucleus. Due to this size decreases.)

• Metallic character (tendency to loss an electron) of an element decreases because of increase in effective nuclear charge.

• Non-metallic character increases along the period. Because of increase in effective nuclear charge.

Atomic number (Z) = Number of protons present in the nucleus.

Answer :-

Na and Cl are in same period. They are expected to have same number of shells.

Option (b) shells

Answer 2

Answer

Option b) shells

$\rule{50}2$

Explanation

Across a period, the number of shells remain constant. Since, Na and Cl are in the same period, they are expected to have same number of shells.

★ Across a period, the valency increases from 1 to 4 and then decreases from 4 to 0.

★ The number of electrons and protons increases across a period as there is an increase in atomic number.

★ The number of shells increases by 1 down a group.

★ Valency remains constant down a group.

★ Atomic size increases down a group.

★ Atomic size decreases across a period.