Page 30 - Chemistry ICSE Class X

18 ICSE Chemistry – 10
(b) The ionisation energy decreases in going from top to bottom in a
ITQWR CPF KV KPETGCUGU KP IQKPI HTQO NGHV VQ TKIJV KP C RGTKQF K G

So, the element at the top of the group on the extreme right (excluding
PQDNG ICUGU YKNN JCXG VJG JKIJGUV KQPKUCVKQP GPGTI[ 6JGTGHQTG atom of
element B is the smallest

y DW> ϭ͘Ϯ͘ Given below are some elements with their atomic radii:
Element Cs Li K Rb Na
Atomic radii (Å)
Infer, to which group of the periodic table they belong, and
how does the atomic radius vary from top to the bottom in a
group of the periodic table.
Solution: 6JGUG GNGOGPVU DGNQPI VQ )TQWR QH VJG RGTKQFKE VCDNG 6JGUG GNGOGPVU
are arranged in the group as shown below:

Element Li Na K Rb Cs
Atomic radii (Å)
Thus, the atomic radius increases in going from top to bottom in a group of the
RGTKQFKE VCDNG
y DW> ϭ͘ϯ͘ Given alongside is a part of the periodic table:
>ŝ Ğ As we move vertically downward from Li to Fr:
EĂ (a) What happens to the size of the atom?
K (b) What happens to their metallic character?
Zď Solution: When we move vertically downward from Li to Fr,
Ɛ C VJG CVQOKE UK\G KPETGCUGU K G (T KU VJG DKIIGUV CVQO
Fr ZĂ D VJG OGVCNNKE EJCTCEVGT KPETGCUGU K G (T KU VJG OQUV OGVCNNKE GNGOGPV

y DW> ϭ͘ϰ͘ Given below is a part of the periodic table:
Li Be B C N O F
Na Mg Al Si P S Cl
As we move horizontally from left to right:
(a) What happens to the metallic character of the elements?
(b) What happens to the atomic size?
Solution: (a) When we move horizontally from left to right, the metallic character
FGETGCUGU K G VJGUG GNGOGPVU HQNNQY VJG QTFGT
Li Be B C N O F
Na Mg Al Si P S Cl
metallic character decreases
(b) When we move horizontally from left to right, the atomic size
FGETGCUGU 5Q

Li Be B C N O F
Na Mg Al Si P S Cl
atomic radius decreases