Assume you have different colored circular discs and a box. Think of a disc as a single atom and color representing an element.

• The box containing one red disc is holding ‘one element’ (Fig. i).
• The box with two red discs apart is again said to be holding ‘one element’ (Fig. ii).
• If the two red discs are overlapped, the box is holding one ‘molecule’; but it can also be said to be holding one element (Fig. iii).
• If the box has one red and one yellow disc apart, it is said to have ‘two elements’ (Fig. iv).
• Now if these two discs are overlapping, the box contains a molecule, more specifically a ‘compound’ (Fig. v) (because it consists of two elements).
• If you add green and blue colored discs it becomes a ‘mixture’! (Fig. vi)

These are illustrated in above figures. Clear?