Question

write any 4 difference between element , compound and mixture

Answer 1

An element contains only atoms with the same number of protons, and hence the same atomic number (although they may have different mass numbers, and should not be referred to as 'identical').

A compound contains atoms of two or more different elements that are chemically combined to form a substance whose physical and chemical properties are different from those of the constituent elements, although determined by them. 

A mixture contains multiple elements or compounds that are mixed together but not chemically bonded. The components can be separated by physical means. 

The elements sodium and chlorine can react to form the compound sodium chloride (salt). If sodium chloride is dissolved in water, the solution is a mixture. The two substances that were mixed can be separated by crystallisation (if you are most interested in the salt) or by distillation (if you are most interested in the water). 

Answer 2

an element:

consists of only one kind of atom
cannot be broken down into a simpler type of matter by either physical or chemical means, and
can exist as either atoms (e.g. argon) or molecules (e.g., nitrogen).

A molecule consists of two or more atoms of the same element, or different elements, that are chemically bound together. Note that the two nitrogen atoms which comprise a nitrogen molecule move as a unit.

a compound:

consists of atoms of two or more different elements bound together
can be broken down into a simpler type of matter (elements) by chemical means (but not by physical means)
has properties that are different from its component elements, and
always contains the same ratio of its component atoms.

 a mixture:

consists of two or more different elements and/or compounds physically intermingled
can be separated into its components by physical means, and
often retains many of the properties of its components.