Question

In modern perodic table how does size vary from down to up why

Answer 1

FROM DOWN TO UP SIZE DECREASES

BECAUSE

NO OF ELECTON INCREASES AND ALSO SHELL INCREASE

AND (Z)*EFF IS A TYPE OF FORCE WHICH DECREASES

(Z)eff defination

force between nucleus and ELECTROn is last shell of any element

hope it will help u

Answer 2

$\bold{Modern \: periodic \: table}$

Modern periodic table is a table in which elements are arranged in groups and periods according to their atomic number.

◼Periodic table follows some periodic table like atomic radius .

$\bold{ATOMIC \: RADIUS}$

It is the distance between the centre of nucleus to the outermost shell of an isolated gaseous atom.

Its dependence:-

▶Number of shells

Number of shells increases so more will be the distance between centre of nucleus to the outermost shell so atomic radius increases .

▶Nuclear charge

Nuclear charge increases so more force will be applied on the electrons and more they will be attracted towards nucleus so the atomic radius will decrease.

◼Across a period

✳Number of shells remains same but the nuclear charge increases so the electrons are attracted towards nucleus hence, the atomic size decreases.

✳White inert gases have outermost shell completely filled so due to repulsion of electrons their atomic size remains big.

◼Across a group

✳In a group the number of shells so the atomic size increases, nuclear charge increases so atomic size should decrease but since number of shells dominates over nuclear charge so it increases.