Page 152 - Chemistry ICSE Class IX

140 ICSE Chemistry – 9

ASSIGNMENT 4

Periodicity in groups and periods

ϭ͘ tŚĂƚ ĂƌĞ ƚŚĞ ŚŽƌŝnjŽŶƚĂů ƌŽǁƐ ĂŶĚ ǀĞƌƟĐĂů ĐŽůƵŵŶƐ ŝŶ Ă ƉĞƌŝŽĚŝĐ ƚĂďůĞ ŬŶŽǁŶ ĂƐ͍
Ϯ͘ ;ĂͿ ,Žǁ ŵĂŶLJ ŐƌŽƵƉƐ ĂŶĚ ƉĞƌŝŽĚƐ ĂƌĞ ƚŚĞƌĞ ŝŶ ƚŚĞ ůŽŶŐ ĨŽƌŵ ƉĞƌŝŽĚŝĐ ƚĂďůĞ͍
;ďͿ ,Žǁ ĂƌĞ ƚŚĞƐĞ ŶƵŵďĞƌĞĚ͍
;ĐͿ ,Žǁ ŵĂŶLJ ĞůĞŵĞŶƚƐ ĂƌĞ ƚŚĞƌĞ ŝŶ ĞĂĐŚ ƉĞƌŝŽĚ͍
ϯ͘ ;ĂͿ tŚĂƚ ŝƐ Ă ƉĞƌŝŽĚ ŝŶ ƚŚĞ ƉĞƌŝŽĚŝĐ ƚĂďůĞ͍
;ďͿ ,Žǁ ĚŽ ĂƚŽŵŝĐ ƐƚƌƵĐƚƵƌĞƐ ĐŚĂŶŐĞ ŝŶ Ă ƉĞƌŝŽĚ ǁŝƚŚ ĂŶ ŝŶĐƌĞĂƐĞ ŝŶ ĂƚŽŵŝĐ ŶƵŵďĞƌ͍
ϰ͘ ZĞǁƌŝƚĞ ƚŚĞ ĨŽůůŽǁŝŶŐ ƐƚĂƚĞŵĞŶƚƐ ŝŶ Ă ĐŽƌƌĞĐƚ ĨŽƌŵ ĂŌĞƌ ĐŽƌƌĞĐƟŽŶ͕ ŝĨ ŶĞĐĞƐƐĂƌLJ͘
;ĂͿ WĞƌŝŽĚƐ ĂƌĞ ŚŽƌŝnjŽŶƚĂů ƌŽǁƐ ŽĨ ĞůĞŵĞŶƚƐ͘
;ďͿ 'ƌŽƵƉƐ ŚĂǀĞ ĞůĞŵĞŶƚƐ ǁŝƚŚ ĐŽŶƐĞĐƵƟǀĞ ĂƚŽŵŝĐ ŶƵŵďĞƌƐ͘
;ĐͿ ůĞŵĞŶƚƐ ŝŶ ƚŚĞ ƐĂŵĞ ƉĞƌŝŽĚ ŚĂǀĞ ĞƋƵĂů ǀĂůĞŶĐLJ͘
;ĚͿ /ƐŽƚŽƉĞƐ ĂƌĞ ƚŚĞ ĞůĞŵĞŶƚƐ ŽĨ ƚŚĞ ƐĂŵĞ ŐƌŽƵƉ͘
ϱ͘ 'ŝǀĞŶ ĂůŽŶŐƐŝĚĞ ŝƐ Ă ƉĂƌƚ ŽĨ ƚŚĞ ƉĞƌŝŽĚŝĐ ƚĂďůĞ͘ H He
ƌƌĂŶŐĞ ƚŚĞ ŐŝǀĞŶ ĞůĞŵĞŶƚƐ
>ŝ Ğ E K & Ne
;ĂͿ /Ŷ ƚŚĞ ŽƌĚĞƌ ŽĨ ĚĞĐƌĞĂƐŝŶŐ ƐŝnjĞ ŝŶ ƚŚĞ
Na
WĞƌŝŽĚ _________________________________
K
'ƌŽƵƉ _________________________________
;ďͿ /Ŷ ƚŚĞ ŽƌĚĞƌ ŽĨ ŝŶĐƌĞĂƐŝŶŐ ŵĞƚĂůůŝĐ ĐŚĂƌĂĐƚĞƌ ŝŶ ƚŚĞ Zď
WĞƌŝŽĚ _________________________________ Cs
'ƌŽƵƉ _________________________________
;ĐͿ /Ŷ ƚŚĞ ŽƌĚĞƌ ŽĨ ŝŶĐƌĞĂƐŝŶŐ ĞůĞĐƚƌŽŶĞŐĂƟǀŝƚLJ ŝŶ ƚŚĞ
WĞƌŝŽĚ _________________________________
'ƌŽƵƉ _________________________________
ϲ͘ /Ŷ ǁŚŝĐŚ ƉĂƌƚ ŽĨ Ă ŐƌŽƵƉ ǁŽƵůĚ LJŽƵ ĞdžƉĞĐƚ ƚŚĞ ĞůĞŵĞŶƚƐ ƚŽ ŚĂǀĞ
;ĂͿ ƚŚĞ ŵŽƐƚ ŵĞƚĂůůŝĐ ĐŚĂƌĂĐƚĞƌ ;ďͿ ƚŚĞ ůĂƌŐĞƐƚ ĂƚŽŵŝĐ ƐŝnjĞ͍
ϳ͘ /Ŷ ŐƌŽƵƉ /ƒ ŽĨ ƚŚĞ ƉĞƌŝŽĚŝĐ ƚĂďůĞ͕ ƚŚƌĞĞ ĞůĞŵĞŶƚƐ y͕ z ĂŶĚ  ŚĂǀĞ ŝŽŶŝĐ ƌĂĚŝŝ ϭϯϯ Ɖŵ͕ ϵϱ Ɖŵ͕ ϲϬ Ɖŵ͕ ƌĞƐƉĞĐƟǀĞůLJ͘ 'ŝǀŝŶŐ Ă
ƌĞĂƐŽŶ͕ ĂƌƌĂŶŐĞ ƚŚĞƐĞ ĞůĞŵĞŶƚƐ ŝŶ ƚŚĞ ŽƌĚĞƌ ŽĨ ŝŶĐƌĞĂƐŝŶŐ ĂƚŽŵŝĐ ŶƵŵďĞƌ ŝŶ ƚŚĞ ŐƌŽƵƉ͘
ϴ͘ Ŷ ĞůĞŵĞŶƚ y ůŝĞƐ ŝŶ ƚŚŝƌĚ ƉĞƌŝŽĚ ĂŶĚ ŐƌŽƵƉ ϭϳ͘ &ŝŶĚ ŽƵƚ͕ ;ĂͿ ƚŚĞ ŶƵŵďĞƌ ŽĨ ǀĂůĞŶĐĞ ĞůĞĐƚƌŽŶƐ ŝŶ ŝƚƐ ĂƚŽŵ͕ ;ďͿ ǀĂůĞŶĐLJ ŽĨ ƚŚĞ
ĞůĞŵĞŶƚ y͕ ;ĐͿ ŶĂƚƵƌĞ Ͳ ŵĞƚĂůůŝĐ Žƌ ŶŽŶŵĞƚĂůůŝĐ͕ ;ĚͿ ŶĂŵĞ ŽĨ ƚŚĞ ĞůĞŵĞŶƚ͘

Illustrative Questions

Q.1. State one reason for keeping chlorine and bromine in the same group of the periodic table.
Ans. Both chlorine and bromine are similar in their chemical behaviour.
Both these elements, chlorine and bromine, have 7 electrons in their outermost shells, i.e., both show a valency
of –1.
Q.2. Which of the following halogens show the least reactivity towards hydrogen? Chlorine, Bromine, Iodine
Ans. The reactivity of halogens decreases in going from uorine to iodine. So, iodine shows the least reactivity towards
hydrogen.
Q.3. From the stand point of atomic structure, what determines which element will be the rst and which one will be
the last in a period of the periodic table?
Ans. The rst element in a period of the periodic table has only one electron in its outermost shell. The last element in
a period of the periodic table has 8 electrons in its outermost shell.
Q.4. Write the electronic con gurations of potassium, lithium, uorine and chlorine, and explain why
(a) potassium is more reactive than lithium.
(b) uorine is more reactive than chlorine.