Question

(a) What is an atom? How do atoms usually exist?
(b) What is a molecule? Explain with examples.
(c) What is the difference between the molecule of an element and the molecule of a
Compound?
Give one example of each.

Answer 1

Hint: Matter is anything that occupies space and has some mass .An atom is the basic structural unit of substance or matter that we see around us. The concept of atoms, molecules, elements and compounds is important to study the fundamentals of chemistry and also important in studying chemical reactions.

Complete answer:
(a) Atoms are the basic building blocks of substances or matter (elements or compounds) around us. The atoms usually exist in the combined state as molecules or ions as these are highly reactive. These thus take part in the chemical reactions for example Hydrogen, Nitrogen, Chlorine etc. However some atoms exist in free form for example noble gases like Helium, Neon, Argon etc.
(b) Atoms generally combine together to form the molecules. Molecules are the smallest particle of a substance. Atoms usually exist in Free State in molecules. Molecules may contain atoms of the same type. For example- Hydrogen $(H_2)$ molecule or may be of different types. For example- Nitric oxide $(NO)$ molecule. Molecules can be Monatomic (with single atom), diatomic (with 2 atoms), triatomic (with 3 atoms) etc.
(c)The molecules can be of 2 types-Molecules of elements or Molecules of compounds.
When atoms of the same elements combine to form molecules it is called Molecule of elements.
For example-Hydrogen molecule $(H_2)$, Oxygen Molecule $(O_2)$ etc.
When atoms of different elements combine to form molecules it is called a molecule of compounds.
For example-Water $(H_{2}O)$, Carbon dioxide $(C{O}_2)$ etc.

Note:
Atoms are too small and cannot be seen through naked eyes. These can be seen only through a high power Electron Microscope. Atoms consist of nucleus containing protons and neutrons and electrons surrounding it. When a neutral atom gains or loses electrons it forms Anion and Cation respectively.