Which letter indicates a subatomic particle with a mass of 5.489 x 10-4 amu

electron

Explanation:

The electron is subatomic particle that revolve around outside the nucleus and has negligible mass. It has a negative charge.

Symbol = e⁻

Mass = 9.10938356×10⁻³¹ Kg

Mass in amu = 1/1838 = 5.4 × 10⁻⁴amu

It was discovered by j. j. Thomson in 1897 during the study of cathode ray properties.

While neutron and proton are present inside the nucleus. Proton has positive charge while neutron is electrically neutral. Proton is discovered by Rutherford while neutron is discovered by James Chadwick in 1932.

Symbol of proton= P⁺

Symbol of neutron= n⁰  

Mass of proton=1.672623×10⁻²⁷ Kg

Mass of neutron=1.674929×10⁻²⁷Kg

An atom consist of electron, protons and neutrons. Protons and neutrons are present with in nucleus while the electrons are present out side the nucleus.

All these three subatomic particles construct an atom

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