# Which is the correct order of atomic sizes?(At. Nos. : Ce = 58, Sn = 50, Yb = 70 and Lu = 71) Option 1) $Ce>Sn>Yb>Lu$ Option 2) $Sn>Ce>Lu>Yb$ Option 3) $Lu>Yb>Sn>Ce$ Option 4) $Sn>Yb>Ce>Lu$

As we learnt in

Application of shielding effect -

1.  It has been used in explaining the inert pair effect.

2.  It has been used to explain the lanthanide and actinide contraction.

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As we move from left to right in a period, there is a decrease in atomic radii. Also, in a group, as the atomic number increases, the atomic radii also increases. So, the atomic number of Sn should have been less than lanthanides. but, because of lanthanide contraction, the atomic radius follows the following trend:

$Ce>Sn>Yb>Lu$

Option 1)

$Ce>Sn>Yb>Lu$

This option is correct.

Option 2)

$Sn>Ce>Lu>Yb$

This option is incorrect.

Option 3)

$Lu>Yb>Sn>Ce$

This option is incorrect.

Option 4)

$Sn>Yb>Ce>Lu$

This option is incorrect.

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