The correct order of atomic radius of Li, Na, Be and O is

The correct order of atomic radius of Li, Na, Be and O is

”Na
”Na
”Be
”O
This question was previously asked in
UPSC CDS-1 – 2024
The correct order of atomic radius from largest to smallest is Na > Li > Be > O.
Atomic radius increases down a group in the periodic table due to the addition of electron shells. Atomic radius generally decreases across a period from left to right due to increasing effective nuclear charge pulling the valence electrons closer to the nucleus.
– Na (Sodium) is in Group 1, Period 3. It has three electron shells.
– Li (Lithium), Be (Beryllium), and O (Oxygen) are all in Period 2. They have two electron shells.
– Comparing Na and Li: Na is below Li in Group 1, so Na > Li in atomic radius.
– Comparing Li, Be, and O: They are in Period 2. Moving from left to right, atomic radius decreases. So, Li > Be > O.
Combining these, the order from largest to smallest is Na > Li > Be > O.
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