In: Chemistry
Which of these correctly is identified in terms of increasing 1st ionization energy?
A. C < N < O
B. Ne < P < Mg
C. F < Cl < Br
D. Cs < Na < I
E. Ca < Ba < At
When we Move from left to right across a period the first ionization energy generally increases. This is because the atomic radius generally decreases moving across a period.
When we move down a group first ionization energy decreases.This is because the atomic radius generally increases moving down a group
Consider
A. C < N < O
In general across a period ionisation energy increases but here nitrogen having a stable half filled orbital state is more stable than oxygen Hence ionisation energy of nitrogen is greater than oxygen
So, 'A' is wrong
B. Ne < P < Mg
Neon being a noble gas it has completely filled orbital state, so it is more stable than P and Mg and it's ionisation energy is greater
So 'B' is wrong
C. F < Cl < Br
Down a group ionisation energy decreases so we should have F > Cl > Br
So 'C' is wrong
D. Cs < Na < I
Down a group ionisation energy decreases so Na > Cs now consider Na and I here iodine has a smaller size compared to that of Sodium so ionisation energy of iodine is greater than sodium hence the order is I > Na > Cs ==>
Cs < Na < I
So, 'D' is correct
E. Ca < Ba < At
Down a group ionisation energy decreases so Ca > Ba but given Ca < Ba so it's wrong
Hence D is correct