An element is called a free state of an element in the presence of an element.
Elemental matter is composed of the same element of pure matter.
Compounds are sub-states called molecular compounds, such as water, sugar and so on. Compounds are ionically bonded as ionic compounds, such as salt, mirabilite and the like. The compound may be represented by a chemical formula consisting of the symbols of the elements contained in the compound. For example, binary compounds consisting of two elements, in writing their chemical formula, as the name of its English name, metal elements written in the former, and less metal followed. Such as salt (sodium chloride) chemical formula for the NaCl. When the number of atoms in the different elements of the compound is not equal, the ratio can be written under the symbol. If the chemical formula of sucrose is C12H33O11, it means that the sugar consists of twelve carbon atoms, twenty-two hydrogen atoms, and eleven oxygen atoms.
The compound is a pure substance consisting of two or more different elements. The different atoms that make up the compound must be present in a certain proportion, in other words, the compound has a certain composition regardless of the source. In daily life, sodium chloride, and distilled water (water), are common compounds. From these compounds, it is found that their properties are different from each other, the salt is composed of sodium atoms and chlorine atoms; sugar is composed of carbon, hydrogen and oxygen atoms; hydrogen in the combustion of oxygen reaction generated water. These facts indicate that two or more substances can react to produce a new substance, which is the compound. The nature of the new material is completely different from the nature of the substance. Usually chemically in this way to determine whether the nature of the compound is a compound. And if a pure can be broken down into two or more than the quality of the original quality of the compound. Such as molten salt, through the current, can be completely broken down into sodium and chlorine atoms, so the salt as a compound.
