Name two elements that exist in the form of atoms.

All matter is made of small indivisible particles called atoms. Atoms, however, do not have an independent existence, in general. They generally exist in combination with other atoms in the form of molecules or ions. Molecules are thus, the smallest particles of various substances (elements or compounds) which have an independent existence. The number of atoms present in one molecule is called atomicity.

Answer the following questions after reading the paragraph.

(1) Write any specific name given the molecule containing the same atoms.

(2) Name two elements whose atoms exist independently.

(3) Atomicity of a molecule of sulphuric acid is

(a) 8 (b) 7 (c) 6 (d) 4

(4) Which of the following elements exhibits the atomicity of eight?

(a) Phosphorus (b) Sulphur (c) Boron (d) Oxygen

Name the following-

Existence of an element in more than one form in the same physical state.

An element E exists in three allotropic forms A, B and C. In allotrope A, the atoms of element E are joined to form spherical molecules. In allotrope B, each atom of element E is surrounded by three other E atoms to form a sheet-like structure. In allotrope C, each atom of element E is surrounded by four other E atoms to form a rigid structure.
(a) Name the element E.
(b) What is allotrope A?
(c) What is allotrope B?
(d) What is allotrope C?
(e) Which allotrope is used in making jewellery?
(f) Which allotrope is used in making the anode of a dry cell?

Name two elements that exist in the form of molecules.