What is the difference between the terms “element”, “compound”, “molecule”, and “salt”?

See explanation

Explanation:

Any substance that contains only one kind of an atom is known as an element. Each element is represented by a unique symbol. The notation for each element can be found on the periodic table of elements.

An example is Sodium (Na), Helium (He), Carbon (C)

The elements can be divided into three categories that have characteristic properties: metals, nonmetals, and semimetals

All elements have some of the same structural components. Each atom of an element has three main components:

⇒ electrons = negative charged

⇒ protons = positive charged

⇒ neutrons = neutral

Both protons and electrons are in the center of the atom, forming the nucleus.

Electrons, meanwhile, have a negative charge and are outside the nucleus. All of these particles, the electrons, protons, and neutrons, are collectively called subatomic particles and they determine the size, charge, physical and chemical properties which determine the unique identity all elements

A compound is a substance that is composed from two or more different elements.

Water (H2O),  carbon dioxide (CO2), methane (CH4)   are a few examples of compounds. They are compounds because they each contain more than one kind of element.

Metals often react with nonmetals to form ionic compounds. These compounds are composed of positive and negative ions formed by adding or subtracting electrons from neutral atoms and molecules.

Nonmetals combine with each other to form covalent compounds, which exist as neutral molecules.

A molecule is formed when two or more atoms join together chemically.

But actually, a compound is a type of molecule. All compounds are molecules, but not all molecules are compounds.

An oxygen molecule, consists in 2 O-atoms. This is only composed from 1 element, not 2 or more.

A salt is a compound made of the non-hydrogen part of an acid and the non-hydroxyl part of a base, the hydrogen and the hydroxide are removed to form water.  All salts are compounds. But not all compounds are salts. (All ionic compounds are salts).

For example,

Cu(OH)2 + H2SO4 → CuSO4 + 2H2O

The non-hydrogen part of H2SO4 is SO42- will react with the non-hydroxyl part of the base ( Cu2+). To form the salt CuSO4 and water.

Another way to form a salt is to react a metal with an acid.

For example:

Mg + 2HNO3 →  Mg(No3)2 + H2

The result is the salt Mg(NO3)2 and hydrogen.

Element is simplest form of matter which can never be broken into any simpler substance by any chemical or physical means

Compound

Is the substance formed when two or more element chemically combined together

Molecule

Is electrically neutral group of two or more atoms hold together by chemical bonds (electrically neutral means unreactive ie chemically stable)

Salt is other compound than water which formed when an acid and base combined together