Explanation

• Magnesium (Mg) is an element, not a compound.
• It is a pure substance made up of only one type of atom.
• Whereas compounds are made up of two or more different elements.

Examples of compounds:

• Water (H2O) - Compound of Hydrogen and Oxygen
• Common salt (NaCl) - Compound of Sodium and Chlorine
• Washing soda (Na2CO3) - Compound of Sodium, Carbon, and Oxygen
• Carbon dioxide (CO2) - Compound of Carbon and Oxygen
  
• Sugar (C6H12O6) - Compound of Carbon, Hydrogen, and Oxygen