Question

Which of the following elements are metals?
(This question has multiple correct option)
A) Calcium
B) Chlorine
C) Potassium
D) Sulphur

Answer 1

Hint: The metals have low ionization enthalpy and are good conductors of heat and electricity. They are lustre, malleable, and ductile. The metals are reactive towards the acid. All s-block elements are metals.


Complete step by step answer:
The s-block elements (alkali earth metal and alkaline earth metal) are metals.
All metals have characteristic physical properties as:
1) They have low ionization enthalpy and therefore they are exceptionally good conductors of heat and electricity.
2) They have the characteristics metallic lustre-they are bright, shiny, and highly reflective.
3) They are malleable and ductile.
4) Their crystal structures are almost always cubic close-packed, hexagonal close-packed, or body-centred cubic.
5) They have very low cohesive forces which are responsible for holding the atoms together, thus they have low melting and boiling points.
Let us have a look at the options.
a) The potassium is an alkali earth metal. It is a group 1 element. Its electronic configuration is
$\text{ K= }\left[ \text{Ar} \right]\text{4}{{\text{s}}^{\text{1}}}$
The potassium can easily lose its electron. Thus it has low ionization enthalpy and it is a good conductor of electricity and heat. Due to low cohesive energy (it is the force that holds the atoms or ions together in solid) of potassium$\text{ }90\text{ kJ mo}{{\text{l}}^{\text{-1}}}$ , it has low melting and boiling point (MP is $\text{ 6}{{\text{3}}^{\text{0}}}\text{C}$ and BP is$\text{ 76}{{\text{6}}^{\text{0}}}\text{C}$ ).on burning It produces the purple-coloured flame. Potassium has a low density. Thus potassium has all the physical properties which metal has. Therefore potassium is a metal.
It vigorously reacts with water. Since it follows possess characteristic properties of the metal. Potassium is a metal.
b) Calcium is an alkaline earth metal. It is a group 2 element. The electronic configuration of calcium is as,
$\text{ Ca= }\left[ \text{Ar} \right]\text{4}{{\text{s}}^{2}}$
It has two electrons in the valence shell. Calcium is shiny, opaque, and malleable. The calcium can lose its two-electrons. But the first ionization enthalpy $590\text{ kJ mo}{{\text{l}}^{\text{-1}}}$ is lower than that of the second ionization enthalpy $1145\text{ kJ mo}{{\text{l}}^{\text{-1}}}$.the calcium conducts the electricity. The calcium is shiny and its metallic surface corrodes on oxidation.
The metals undergo the characteristic reaction. When a metal reacts with the acid a salt and hydrogen gas is produced. The general reaction is
$\text{ Metal(M) + Acid}\to \text{Salt + Hydrogen gas (}{{\text{H}}_{\text{2}}}\text{)}$
The potassium reacts with the hydrochloric acid $\text{ (HCl)}$and forms a potassium chloride $\text{ (KCl)}$and liberates hydrogen gas.
$\text{ 2K + 2HCl}\to \text{ 2KCl + }{{\text{H}}_{\text{2}}}(\uparrow )$
Similarly, the calcium reacts with the acid.
$\text{ Ca + }{{\text{H}}_{\text{2}}}\text{S}{{\text{O}}_{\text{4}}}\to \text{ CaS}{{\text{O}}_{\text{4}}}\text{ + }{{\text{H}}_{\text{2}}}(\uparrow )$
The ${{\text{H}}_{\text{2}}}$gas burns with the pop sound, Confirms the presence of metal
Therefore calcium possesses the distinctive properties of the metal.

Hence, (A) and (C) are the correct option.


Note: Remember that the s-block elements are metals. According to the periodic table, the alkali and alkaline earth metal carry all the necessary properties of the metal. The sulphur and chlorine are non-metal; they do not easily lose electrons.