Name the twenty most common elements?

Elements:

• A species of atoms with the same number of protons in their atomic nuclei is what we refer to as an element.
• The number of protons in an element's atoms is always the same, but the number of neutrons and hence the mass might vary.

Common Elements:

• Hydrogen, $\mathrm{H}$
• Helium, $\mathrm{He}$
• Carbon, $\mathrm{C}$
• Nitrogen, $\mathrm{N}$
• Oxygen, $\mathrm{O}$
• Sodium, $\mathrm{Na}$
• Aluminium, $\mathrm{Al}$
• Potassium, $\mathrm{K}$
• Calcium, $\mathrm{Ca}$
• Iron, $\mathrm{Fe}$
• Nickel, $\mathrm{Ni}$
• Copper, $\mathrm{Cu}$
• Zinc, $\mathrm{Zn}$
• Silver, $\mathrm{Ag}$
• Tin, $\mathrm{Sn}$
• Mercury, $\mathrm{Hg}$
• Gold, $\mathrm{Au}$