Answer: 9
Atomic number |
Ionization Enthalpy (kJ/mol) |
I1 |
I2 |
I3 |
n |
1681 |
3374 |
6050 |
n + 1 |
2081 |
3952 |
6122 |
n + 2 |
496 |
4562 |
6910 |
n + 3 |
738 |
1451 |
7733 |
By observing the values of I1, I2 & I3 for atomic number (n+2), it is observed that I2 >>I1. This indicates that number of valence shell electrons is 1 and atomic number (n+2) should be an alkali metal.
Also for atomic number (n+3), I3 >> I2.
This indicates that it will be an alkaline earth metal which suggests that atomic number (n+1) should be a noble gas & atomic number (n) should belong to Halogen family. Since n < 10; hence n = 9 (F atom)
Note : n = 1 (H atom) cannot be the answer because it does not have I2 & I3 values.