Question

Which of the following compounds contain no covalent bonds?
$KCl,PH_3,O_2,B_2H_6,H_2SO_4$

Answer 1

When we need to find the number of covalent bonds then we should know that a covalent bond is always formed between two nonmetals and an ionic bond is always formed between a metal and one non metal.

Complete step-by-step answer: As we have already discussed that a when we need to find number of covalent bonds then we should know that a covalent bond is always formed between two non metals and ionic bond is always formed between a metal and one non metal.
In $KCl$
$K$ is a metal and cl is a non metal .hence,it is an ionic bond.so, it will have no covalent bond present.
In $PH_3$
It is a covalent polar compound.in this phosphorus is bonded to three hydrogen atoms.since the electronegativity of phosphorus is nearly same as that of hydrogen so,there is a covalent
Bond present but non polar in nature.
In $O_2$
Oxygen shows a pair of doubly bonded covalent bonds as both are non meta.as there are two lone pairs present on each oxygen atom so,they form the bond and finally results in doubly bonded covalent bond.
In $B_2H_6$
This is called diborane.it shows covalent bonding.as there is bonding between boron and hydrogen .
In $H_2SO_4$
Sulphuric acid is the one which has both covalent bond as well as ionic bond.the oxygen is covalently bonded to the sulphur and the hydrogen is always bonded to the two oxygen atoms by the ionic bond.

Hence $KCl$ is one which does not have any covalent bond.

Note: Covalent bonds are always organic in nature.Ionic bonds are always inorganic in nature.covalent bonds are also affected by the electronegativity of the connected atoms which determines the chemical polarity of the bond.