The mass number of potassium is ______________.

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SSC CGL 2022 Tier-I Official Paper (Held On : 08 Dec 2022 Shift 4)
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  1. 39
  2. 40
  3. 38
  4. 37

Answer (Detailed Solution Below)

Option 1 : 39
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Detailed Solution

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The correct answer is 39.

Key Points

  •  We know that mass no. is given as,
    • Mass no.= No. of protons + No. of neutrons.
  • Potassium has an atomic number of 19, and an element's atomic number is determined by how many protons it contains.
  • Hence, potassium contains 19 protons.
  • Twenty neutrons make up potassium.
  • The mass number of potassium is calculated using the formula above as,
    • Mass no. = 20+19=39. 

Additional Information

  • Potassium is a member of the alkali group of the periodic table.
    • Symbol: K.
    • Atomic number: 19.
    • Belongs to group 1 in the periodic table.
    • First isolated in 1807 by Humphry Davy.
    • Sodium and Potassium are the elements known as soft metals(can cut with a knife with little force).
    • Potassium metal is kept in kerosene due to its high reactivity with water.
    • Potassium bicarbonate is the chemical used in fire extinguishers.
    • Potassium is the most common radioisotope in the human body.
    • Potassium is the second least dense metal after lithium.
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