Concept:Ionization energy generally increases across a period from left to right and decreases down a group.
Explanation:Across a period, nuclear charge increases, so electrons are held more tightly and ionization energy increases.
Down a group, atomic size increases and shielding increases, so ionization energy decreases.
Check each series:
A. Li, Na, K is down Group 1, so ionization energy decreases, not increases.
B. B, Be, Li is not the correct increasing order because Be has a higher ionization energy than B due to its stable filled
2s subshell.
C. O, F, Ne are in Period 2 moving from left to right, so their ionization energy increases in that order.
D. Be, Mg, Ca is down Group 2, so ionization energy decreases, not increases.
Answer:Option C:
O,F,Ne