Answer: Option (A) is the correct answer.
Explanation:
Substances or elements which lose electrons are known as metals whereas elements which gain electrons are known as non-metals.
For example, electronic configuration of hafnium is [tex][Xe]4f^{14}5d^{2}6s^{2}[/tex]. It is a transition metal as it has incompletely filled d-orbital so, it will lose electrons to attain stability.
Electronic configuration of radon is [tex][Xe]4f^{14}5d^{10}6s^{2}6p^{6}[/tex]. Since it is a noble gas it has completely filled orbitals so, it will neither lose nor gain electrons.
Electronic configuration of silicon is [tex][Ne]3s^{2}3p^{2}[/tex] and it is a non-metal. So, it will gain electrons to complete its octet.
Electronic configuration of sulfur is [tex][Ne]3s^{2}3p^{4}[/tex] and it is a non-metal. So, it will gain electrons to complete its octet.
Electronic configuration of selenium is [tex][Ne]3d^{10}4s^{2}4p^{4}[/tex] and it is a non-metals. So, it will gain electrons to complete its octet.
Hence, we can conclude that out of the given options hafnium (Hf) is the element which is a metal.
