Compounds:
Various elements can join altogether, sharing electrons. Whenever this occurs, the outcome is a chemical compound. One of the most general compounds on Earth is water, the product of two hydrogen atoms joining with an atom of oxygen. There are thousands of various chemical compounds which occur in nature.
NOT JUST A MIXTURE!
A compound is not a similar thing as a mixture of elements. At times, though, whenever elements are mixed (and, if essential, given a jolt of energy), compounds result since the elements undergo chemical reactions with each other. When hydrogen and oxygen are mixed, the outcome is an odorless colorless, gas. A spark will cause the molecules to join altogether to form water-vapor. This reaction will liberate energy in the form of heat and light. Under the exact conditions, there will be an explosion as the two elements join eagerly. Whenever atoms of elements join together to form a compound, then the resultant particles are molecules. The figure shown below is a basic diagram of a water molecule.
Figure: Basic diagram of a water molecule.
Compounds frequently, but not always, emerge different from any of the elements which make them up. At room temperature and pressure, both oxygen and hydrogen are gases. But water in the same conditions is a liquid. The heat of the reaction just explained, if done in the real world, would outcome in water vapor initially, and water vapor is an odorless colorless, gas. Though, some of this vapor would condense into liquid water when the temperature got low sufficient for dew to form. A few of it would become solid, snow, forming frost, or ice when the temperature dropped below the freezing point of water.
A note of concern: Do not try an experiment like this! You could be rigorously burned. In the severe, if adequate of the hydrogen-oxygen air is inhaled, your lungs will be wounded to the point where you may die of asphyxiation. We at times read or hear news reports about home experimenters who blew themselves up with chemistry sets. Do not become the subject matter for one of these stories!
The other common instance of a compound is rust. These forms whenever iron combines with oxygen. Iron is a dull gray solid, and oxygen is a gas; though, iron rust is a maroon-red or brownish powder, totally unlike either of the elements from which it is created. The reaction between iron and oxygen occurs slowly, unlike the fast combination of hydrogen and oxygen whenever ignited. The rate of the iron-oxygen reaction can be sped up by the presence of water, as anybody who lives in a humid climate knows.