Which of the following group of elements are diamagnetic ? A) Argon, copper, silver B) Hydrogen, argon, copper C) Oxygen, copper, silver D) Hydrogen, oxygen, Argon

The substances that are usually repelled by magnets or external magnetic field are known as diamagnetic substances.
Properties of a diamagnetic substance is given by,
*A substance that has only paired electrons, no unpaired electrons.
*Since the electrons are paired net magnetic moment is zero
*There are no atomic dipoles in a diamagnetic material
*Feebly repelled by magnets so in non uniform field the diamanetic substance shows a tendancy to move from strong to week part of the external magnetic field.
Diamagnetism is a property of all of substances. But when multiple forms of magnetism (paramagnetism, ferromagnetism...) are present in a substance, the contribution of diamagnetism is usually negligibly small.
The electronic configuration of Argon is given by,
$[Ar]=1s^{2}2s^{2}2p^{6}3s^{2}3p^6$
Since all the electrons are paired, Argon is diamagnetic.
The electronic configuration of Silver is given by,
$[Ag]=[Kr]4d^{10}5s^1$
In the case of Silver the contribution of diamagnetism by inner shell electrons is much greater than that of paramagnetism produced by single electron in the 5s orbital. Therefore Silver is diamagnetic.
The electronic configuration of Copper is given by,
$[Cu]=1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^9$
As silver, the contribution diamagnetism by inner shells of copper is greater than that of paramagnetism produced by outer unpaired electron. Therefore Copper is diamagnetic.
Answer: (A) Argon, Copper, Silver