Question

The first ionisation potential of $Na,\,Mg,\,Al$ and $Si$ are in the order:

• A. $Na < Mg < Al < Si$
• B. $Na < Al < Mg < Si$
• C. $Na>Mg>Al>Si$
• D. $Na < Si < Al < Mg$

Answer 1

Answer: (B)

$Na < Al < Mg < Si$

Answer 2

The first ionisation potential is the energy required to pull out first electron from the outer most orbit. The sequence for this is as follows $Na < Al < Mg < Si$ The first ionisation potential increases along the period from left to right.