Question

Which of the following is not a non-metal?
(A) Hydrogen
(B) Silicon
(C) Mercury
(D) Chlorine

Answer 1

Elements that are not non-metals are known as metals. So, to solve this question we first need to know what nonmetals are and how to differentiate them from metals. Elements that do not have metal-like properties are known as non-metals.

Complete answer:
- Non-metals are generally electronegative whereas metals are generally electropositive.
- Non-metals are not lustrous whereas metals are lustrous.
- Non-metals cannot be made into thin wires i.e., are not ductile and cannot be beaten into thin sheets i.e., are not malleable whereas metals can be.
- Non-metals do not displace hydrogen atoms upon reaction with acids whereas metals do.
- Non-metals form acidic or neutral oxides upon reaction with oxygen whereas metals form basic oxides upon reaction with oxygen.
- Non-metals are mostly found in the p-block of the periodic table and have either 4, 5, 6, 7, or 8 electrons in their outermost valence shell whereas metals are found in all blocks of the periodic table and usually have 1, 2, or 3 electrons in its outermost shell.
- Non-metals form both covalent and ionic bonds whereas metals only form ionic bonds.
Now, let us determine which among the given elements is not a non-metal based on the above-mentioned properties.
(A) Hydrogen is generally considered to be a non-metal as it is a gas in the free state and easily forms anions and mostly forms covalent bonds.
(B) Silicon is a non-metal as it has 4 electrons in its outermost shell. Since it shows various properties as that of a metal, it is also considered to be a metalloid.
(C) Mercury is metal as it has two electrons in its valence shell. It is the only metal to exist in the liquid state at room temperature.
(D) Chlorine is a non-metal as it has 7 electrons in its valence shell and exists as a gas in the free state. It readily forms anions and mostly forms covalent bonds.

So, the correct answer is option (C) Mercury.

Note:
This question can be confusing as hydrogen, silicon, and mercury show properties of both metals and nonmetals. So, we should keep in mind the properties that are exclusively shown either by metals or by non-metals to make the distinction.