Question

Heaviest atom among the following is:
a.) Uranium
b.) Lead
c.) Mercury
d.) Radium

Answer 1

Hint: Atom is a constituent unit of a matter in which matter can be divided without the release of any charge particle. Heaviness of any atom will be decided by its mass number. Higher the value of mass number, heavier the atom will be and mass number is actually the sum of total number of neutrons and protons present in the nucleus of an atom.

Complete Solution :
- Uranium: Number of protons in an atom of U-92 is 92 and number of neutrons is 146 and its mass number is the sum of 92 and 146 which comes equal to 238.
- Lead: Number of protons in an atom of Pb-82 is 82 and number of neutrons is 125 and its mass number is the sum of 82 and 125 which comes equal to 207.
- Mercury: Number of protons in an atom of Hg-80 is 80 and number of neutrons is 121 and its mass number is the sum of 80 and 121 which comes equal to 201.
- Radium: Number of protons in an atom of Ra-88 is 88 and number of neutrons is 138 and its mass number is the sum of 88 and 138 which comes equal to 226.
So clearly among all four elements, uranium is the heaviest element.
So, the correct answer is “Option A”.

Note: - Uranium is naturally radioactive: Its nucleus is unstable, so the element is in a constant state of decay, seeking a more stable arrangement.
- Lead (Pb) is a heavy metal that is denser than most common materials. It is soft and malleable, and also has a relatively low melting point. Mercury (Hg) is a heavy, silvery-white liquid metal. Compared to other metals, Hg is a poor conductor of heat, but a fair conductor of electricity. Radium (Ra) is silvery, lustrous, soft, intensely radioactive metal.