Answer :
Compound : It is a mixture of elements which are chemically bonded together in a fixed proportions.
(a) Citric acid, ![C_6H_8O_7](https://tex.z-dn.net/?f=C_6H_8O_7)
In this compound, there are three types of elements present carbon, hydrogen and oxygen. There are 6 atoms of carbon element, 8 atoms of hydrogen element and 7 atoms of oxygen element.
(b) Glycine, ![C_2H_5NO_2](https://tex.z-dn.net/?f=C_2H_5NO_2)
In this compound, there are four types of elements present carbon, hydrogen, nitrogen and oxygen. There are 2 atoms of carbon element, 5 atoms of hydrogen element, 1 atom of nitrogen element and 2 atoms of oxygen element.
(c) Chloroform, ![CHCl_3](https://tex.z-dn.net/?f=CHCl_3)
In this compound, there are three types of elements present carbon, hydrogen and chlorine. There are 1 atom of carbon element, 1 atom of hydrogen element and 3 atoms of chlorine element.
(d) Sulfur hexafluoride, ![SF_6](https://tex.z-dn.net/?f=SF_6)
In this compound, there are two types of elements present sulfur and fluorine. There are 1 atom of sulfur element and 6 atoms of fluorine element.