The atom is the smallest basic unit of matter which comprises of a central nucleus surrounded by a cloud of revolving electrons. The word 'atom' is derived from the greek word 'atomos' which means 'indivisible'. Over 99.9% of the mass of an atom is concentrated in its nucleus.
Though atom originally denoted an indivisible particle of matter, it is composed of various subatomic particles. Some of the prominent subatomic particles are:
Proton:
The proton is a baryon (a subatomic hadron particle) with one positive electric charge. Its charge is equal to 1.602176565(35) × 10−19 C and its mass is equal to 1.672621777(74) × 10−27 kg which is 1836 times the mass of an electron. Along with neutrons, protons constitute the nucleus of an atom. Proton was discovered by Ernest Rutherford in the year 1919.
Neutron:
The neutron is a baryon (a subatomic hadron particle) with no charge. Its mass (1.674927351(74) × 10−27 kg) is nearly equal to the mass of a proton. Stable neutrons are often found as bound neutrons in stable nuclei. Free neutrons are highly unstable in nature. They undergo beta decay with a mean lifetime of about 885.7 seconds. Neutron was discovered by Sir James Chadwick in the year 1932.
Electron:
The electron is a lepton (a subatomic particle) with one negative electric charge. Electrons are one of the lightest subatomic particles. They constitute less than 0.06% of the total mass of an atom. The mass of an electron is equal to 9.10938291(40) × 10−31 kg and the charge of an electron is equal to -1.602176565(35) × 10−19 C. Electrons revolve around the positively charged nucleus (made of protons and neutrons) of an atom. In a neutral atom, the number of electrons will be equal to the number of protons (Electrons neutralize the positive charge of the protons). Electron was discovered by J.J. Thomson and his team in the year 1897.
Apart from the above particles, an atom may also consist of various other subatomic particles. These include other leptons, baryons and mesons.
Though atom originally denoted an indivisible particle of matter, it is composed of various subatomic particles. Some of the prominent subatomic particles are:
Proton:
The proton is a baryon (a subatomic hadron particle) with one positive electric charge. Its charge is equal to 1.602176565(35) × 10−19 C and its mass is equal to 1.672621777(74) × 10−27 kg which is 1836 times the mass of an electron. Along with neutrons, protons constitute the nucleus of an atom. Proton was discovered by Ernest Rutherford in the year 1919.
Neutron:
The neutron is a baryon (a subatomic hadron particle) with no charge. Its mass (1.674927351(74) × 10−27 kg) is nearly equal to the mass of a proton. Stable neutrons are often found as bound neutrons in stable nuclei. Free neutrons are highly unstable in nature. They undergo beta decay with a mean lifetime of about 885.7 seconds. Neutron was discovered by Sir James Chadwick in the year 1932.
Electron:
The electron is a lepton (a subatomic particle) with one negative electric charge. Electrons are one of the lightest subatomic particles. They constitute less than 0.06% of the total mass of an atom. The mass of an electron is equal to 9.10938291(40) × 10−31 kg and the charge of an electron is equal to -1.602176565(35) × 10−19 C. Electrons revolve around the positively charged nucleus (made of protons and neutrons) of an atom. In a neutral atom, the number of electrons will be equal to the number of protons (Electrons neutralize the positive charge of the protons). Electron was discovered by J.J. Thomson and his team in the year 1897.
Apart from the above particles, an atom may also consist of various other subatomic particles. These include other leptons, baryons and mesons.
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