Page 21 - Chemistry ICSE Class X

Periodic Properties and Variations of Properties (Physical and Chemical) 9

ŶƐǁĞƌ ƚŚĞ ĨŽůůŽǁŝŶŐ͗
;ĂͿ ƌƌĂŶŐĞ ƚŚĞ ŵĞŵďĞƌƐ ŽĨ Ă ƉĞƌŝŽĚ ŝŶ ƚŚĞ ŽƌĚĞƌ ŽĨ
;ŝͿ ĚĞĐƌĞĂƐŝŶŐ ĂƚŽŵŝĐ ƌĂĚŝƵƐ ;ŝŝͿ ĚĞĐƌĞĂƐŝŶŐ ŵĞƚĂůůŝĐ ĐŚĂƌĂĐƚĞƌ
;ďͿ ^ĞůĞĐƚ ƚǁŽ ĞůĞŵĞŶƚƐ ĨƌŽŵ ƚŚĞ ŐƌŽƵƉ ƚŚĂƚ ĂƌĞ
;ŝͿ ůĞƐƐ ƌĞĂĐƟǀĞ ƚŚĂŶ ƉŽƚĂƐƐŝƵŵ ;ŝŝͿ ŵŽƌĞ ƌĞĂĐƟǀĞ ƚŚĂŶ ƉŽƚĂƐƐŝƵŵ
ϳ͘ ŽƉLJ ĂŶĚ ĐŽŵƉůĞƚĞ ƚŚĞ ĨŽůůŽǁŝŶŐ ƐĞŶƚĞŶĐĞƐ ĐŚŽŽƐŝŶŐ ƚŚĞ ĐŽƌƌĞĐƚ ǁŽƌĚ Žƌ ǁŽƌĚƐ ĨƌŽŵ ƚŚŽƐĞ ŐŝǀĞŶ ŝŶ ďƌĂĐŬĞƚƐ Ăƚ ƚŚĞ ĞŶĚ
ŽĨ ĞĂĐŚ ƐĞŶƚĞŶĐĞ͘
;ĂͿ DŽǀŝŶŐ ĂĐƌŽƐƐ Ă __________ ŽĨ ƚŚĞ ƉĞƌŝŽĚŝĐ ƚĂďůĞ͕ ƚŚĞ ĞůĞŵĞŶƚƐ ƐŚŽǁ ŝŶĐƌĞĂƐŝŶŐ __________ ĐŚĂƌĂĐƚĞƌ ;ŐƌŽƵƉ͕
ƉĞƌŝŽĚ͕ ŵĞƚĂůůŝĐ͕ ŶŽŶŵĞƚĂůůŝĐͿ
;ďͿ dŚĞ ĞůĞŵĞŶƚ Ăƚ ƚŚĞ ďŽƩŽŵ ŽĨ Ă ŐƌŽƵƉ ǁŽƵůĚ ďĞ ĞdžƉĞĐƚĞĚ ƚŽ ƐŚŽǁ __________ ŵĞƚĂůůŝĐ ĐŚĂƌĂĐƚĞƌ ƚŚĂŶ ƚŚĞ ĞůĞŵĞŶƚ
Ăƚ ƚŚĞ ƚŽƉ ;ůĞƐƐ͕ ŵŽƌĞͿ
;ĐͿ dŚĞ ƐŝŵŝůĂƌŝƟĞƐ ŝŶ ƚŚĞ ƉƌŽƉĞƌƟĞƐ ŽĨ ĞůĞŵĞŶƚƐ ŝŶ Ă ŐƌŽƵƉ ŝƐ ďĞĐĂƵƐĞ ƚŚĞLJ ŚĂǀĞ ƚŚĞ ƐĂŵĞ __________ ;ĞůĞĐƚƌŽŶŝĐ
ĐŽŶĮŐƵƌĂƟŽŶ͕ ŶƵŵďĞƌ ŽĨ ŽƵƚĞƌŵŽƐƚ ĞůĞĐƚƌŽŶƐ͕ ĂƚŽŵŝĐ ŶƵŵďĞƌͿ
ϴ͘ tŝƚŚŝŶ Ă ŐƌŽƵƉ͕ ǁŚĞƌĞ ǁŽƵůĚ LJŽƵ ĞdžƉĞĐƚ ƚŽ ĮŶĚ ƚŚĞ ĞůĞŵĞŶƚ ǁŝƚŚ
;ĂͿ ƚŚĞ ŐƌĞĂƚĞƐƚ ŵĞƚĂůůŝĐ ĐŚĂƌĂĐƚĞƌ ;ďͿ ƚŚĞ ůĂƌŐĞƐƚ ĂƚŽŵŝĐ ƐŝnjĞ͍

Ionisation Energy (or Ionisation Potential)

What is ionisation energy

In an atom, the electrons are held by the electrostatic force of attraction to dŚĞ ƐLJŵďŽů ŽĨ ŝŽŶŝƐĂƟŽŶ ĞŶĞƌŐLJ ŝƐ I͘
VJG RQUKVKXGN[ EJCTIGF PWENGWU 6JGTGHQTG VQ TGOQXG CP GNGEVTQP HTQO CP[
CVQO UQOG GPGTI[ OWUV DG IKXGP VQ VJG CVQO 6JKU GPGTI[ KU GZRTGUUGF KP / ŝƐ ƚŚĞ ĂďďƌĞǀŝĂƟŽŶ ŽĨ ƚŚĞ
ŝŽŶŝƐĂƟŽŶ ĞŶĞƌŐLJ͘
VGTOU QH KQPKUCVKQP GPGTI[ YJKEJ KU FGſPGF CU HQNNQYU
The amount of energy required to remove the most loosely held
electron from an isolated, gaseous atom in its ground state is called
ionisation energy, (I).
The energy absorbed in the following reaction is called the ionisation
GPGTI[ QH VJG GNGOGPV /
+
M(g) + I o M (g) + e –
Units of ionisation energy: Ionisation energy is measured in the units
–1
QH M, OQN QT KP VJG G8 GNGEVTQP XQNV WPKV
G8 RGT CVQO M, OQN –1
What is meant by the successive ionisation energies
For atoms which can lose more than one electron, more than one values of dŚĞ ƚĞƌŵ ŝŽŶŝƐĂƟŽŶ ĞŶĞƌŐLJ ŝƐ ŶŽǁ
VJG KQPKUCVKQP GPGTI[ CTG RQUUKDNG 6JGUG CTG ECNNGF ſTUV UGEQPF VJKTF ĐĂůůĞĚ ďLJ ƚŚĞ ŶĂŵĞ ŝŽŶŝƐĂƟŽŶ
GVE KQPKUCVKQP GPGTIKGU ĞŶƚŚĂůƉLJ
ƒ The energy required to remove one electron from an isolated gaseous
atom in its ground state is called ſTUV KQPKUCVKQP GPGTI[ I )
1
+
M(g) + I o M (g) + e –
1
ƒ The energy required to remove an electron from an isolated gaseous
+
monopositive ion (M ) is called second ionisation energy (I )
2
2+
+
M (g) + I o M (g) + e –
2
ƒ The energy required to remove an electron from an isolated gaseous
2+
divalent ion (M ) is called third ionisation energy (I )
3
2+
3+
M (g) + I o M (g) + e –
3
Since, it is easier to remove electrons from a neutral atom than from a
positively charged ion, hence the ionisation energies generally follow the
order: