when different elements react, their atoms join with other atoms. what type of substance is formed?

When different elements react, their atoms join with other atoms to form a new type of substance called a compound. Compounds are substances that consist of atoms from at least two different elements chemically bonded together. These bonds may be ionic or covalent, and the resulting compounds typically have different properties from the original elements. This formation occurs through chemical reactions where atoms combine in fixed proportions to create compounds, such as water (H2O) or sodium chloride (NaCl).