Question

Which of the following is a non-metal that remains liquid at room temperature?
$Br,Cl,He,P$

Answer 1

Hint – Here we will proceed by checking the boiling state of a non-metal. Then by using the Van der Waals forces (weak London dispersion forces) we will get our answer.

Complete answer:
Van der Waals forces – It is a general term used to define the attraction of intermolecular forces between molecules. There are two kinds of Van der Waals forces that are weak London dispersion forces and strong dipole-dipole forces.
Bromine – It is a non-metallic element found in the halogen group on the periodic table. It has a tendency to gain an electron to form ionic compounds but it is not as electronegative is fluorine and chlorine.
Bromine is a liquid state because the intermolecular forces are strong enough so that it does not evaporate. $Br$ forms diatomic molecules and van der Waals also known as VDW are sufficiently strong. Its electrons are well apart from the nuclei so they are easily distorted.
Bromine $B{r_2}$ is a liquid at standard temperature at pressure while chlorine $\left( {C{l_2}} \right)$ - ${220^ \circ }C,b.p. - {188^ \circ }C$ is above the Bromine in the periodic table and it is in the form of a gas. It is a gas because F-F bond strength is very strong while the London dispersion forces which are responsible for gaseous state are very weak. Then Iodine $\left( {{I_2}} \right)$- ${114^ \circ }C,b.p{.184^ \circ }C$ is below it on the periodic table and it is in the state of a solid because as its atom size is larger, the electrons are so far that electron could get very easily distorted. It has very strong intermolecular London forces which make it a solid.
The boiling point is 137.8 degrees Fahrenheit (58.8 degrees Celsius). As its boiling point, bromine changes in the form of a liquid to a gas. Hence in temperature, between 19 degrees Fahrenheit and 137.8 degrees Fahrenheit, bromine is in the form of a liquid.

Therefore, the correct answer is Bromine $Br$.

Note – Whenever we come up with this type of question, one must know that the bromine is a only liquid non-metal with the atomic number 35. Also, its properties are intermediate between those of Chlorine and iodine. One must know the properties of metals and non-metals solve such types of questions.