Question

Mercury is a liquid metal because:

• A. it has a completely filled $s$-orbital
• B. it has a small atomic size
• C. it has a completely filled $d$-orbital that prevents $d-d$ overlapping of orbitals
• D. it has a completely filled $d$-orbital that causes $d-d$ overlapping

Answer 1

The correct option is A it has a completely filled $s$-orbital

Mercury is a liquid metal because it has a completely filled 6s orbital.
Mercury has a unique electronic configuration which makes the outer orbital close to the nucleus.
$H{g}_{80}$: $1s^2,2s^{2}2p^6,3s^{2}3p^6,4s^{2}3d^{10}4p^6,5s^{2}4d^{10}5p^6,6s^{2}4f^{14}5d^{10}$

An f-shell poorly screens the nuclear charge that stbilizes the 6s orbital. Thus it is impossible to form any bond with other elements. So, mercury is unable to form bond like other solid metals and that's why it remains in liquid form.
Hence, option (A) is correct.