Which of the following value is the Atomic Mass of Calcium ?

The correct answer is Option(2).i.e.40 µ. 

Key Points

• The Atomic Mass of Calcium is 40.078 µ ≈ 40 µ.
• Atom: 
  • An atom is the smallest invisible unit of matter that constitutes a chemical element.
  • Every plasma, solid, gas & liquid, composed of ionized or neutral atoms.
  • Around 100 picometers across, atoms are extremely small. 
• Atomic Mass: 
  • The Atomic Theory of Dalton suggested that each element has a unique atomic mass.
  • The law of constant proportions could be explained easily by the implementation of Dalton's theory.
  • As the size of an atom is relatively small, it is quite difficult to determine the mass of an atom.
  • That's why the scientists started evaluating the mass of an atom by differentiating it with the mass of a standard atom.
  • The atomic mass is 12u (12 atomic mass units).
  • Thus it states that 1 atomic mass = Mass of 1/12 the mass of a carbon-12 atom.
• The following table shows the list of elements with the respective atomic masses. 

  Elements	Atomic Mass
  Hydrogen	1 µ
  Carbon	12 µ
  Nitrogen	14 µ
  Oxygen	16 µ
  Magnesium	24 µ
  Sodium	23 µ
  Calcium	40 µ