Periodic TableEasy
Question
The first ionisation potential of Na, Mg, Al and Si are in the ordrer :
Options
A.Na > Mg < Al < Si
B.Na > Mg > Al > Si
C.Na < Mg < Al > Si
D.Na > Mg > Al < Si
Solution
Writing their E.C.
Na = ls2, 2s2, 2p6, 3s1
Mg = ls2, 2p2, 2p6, 3s2
Al = ls2, 2p2, 2p6, 3s2, 3p1
Si = ls2,2p2, 2p6, 3s2, 3p2
On the basis of ENC, the I E1 must increases from Na to Si because all these belongs to same period. Due to higher ENC and completely filled s-subshell, I. E1 (Na). Although ENC for Al must be greater than ENC for Mg, but in Al electron is released from 3p while in Mg it goes from 3s. Because 3s is closer to nucleas than 3p and in Mg, s-subshell is completely filled also so I. E1 (Mg) > I. E1 (Al). I. E1 (Si) > I. E1 (Al) due higher ENC thus correct order is :
Na < Mg > Al < Si
Na = ls2, 2s2, 2p6, 3s1
Mg = ls2, 2p2, 2p6, 3s2
Al = ls2, 2p2, 2p6, 3s2, 3p1
Si = ls2,2p2, 2p6, 3s2, 3p2
On the basis of ENC, the I E1 must increases from Na to Si because all these belongs to same period. Due to higher ENC and completely filled s-subshell, I. E1 (Na). Although ENC for Al must be greater than ENC for Mg, but in Al electron is released from 3p while in Mg it goes from 3s. Because 3s is closer to nucleas than 3p and in Mg, s-subshell is completely filled also so I. E1 (Mg) > I. E1 (Al). I. E1 (Si) > I. E1 (Al) due higher ENC thus correct order is :
Na < Mg > Al < Si
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