This topic describes the three fundamental sub-atomic particles — electrons, protons, and neutrons — in terms of their charge, mass, and behavior in electric and magnetic fields.
Definition
Sub-Atomic Particles: The particles that make up an atom — electrons, protons, and neutrons.
Main Idea
Atoms are made of three fundamental particles: electrons (negative), protons (positive), and neutrons (neutral). These particles differ in charge, mass, and behavior in electric and magnetic fields. The atom consists of a small, dense nucleus (containing protons and neutrons) surrounded by electrons in orbitals.
Core Concept
The behavior of sub-atomic particles in electric and magnetic fields depends on their charge and mass. Opposite charges attract, like charges repel, and neutral particles are unaffected.
Detailed Explanation
Electron
Negatively charged subatomic particle.
Charge:1.6022 × 10-19 C
Relative charge:-1
Mass:9.1095 × 10-31 kg
Discovered by: J.J. Thomson.
Behavior: Deflected towards the positive pole of an electric field.
These particles are electromagnetic in nature.
Proton
Positively charged subatomic particle.
Charge: Equal to that of electron but opposite in sign.
Mass:1.6727 × 10-27 kg
Relative charge:+1
Mass ratio: 1836 times heavier than an electron.
Behavior: Deflected towards the negative pole of an electric field.
Thus, electron and proton are electromagnetic in nature.
Neutron
No charge (neutral).
Mass:1.6750 × 10-27 kg
Behavior: Passes by the electric and magnetic fields un-deflected.
It is more massive than proton.
Table of Sub-Atomic Particles
Particle
Mass (kg)
Charge (C)
Relative Mass
Relative Charge
Proton
1.672 × 10-27
1.602 × 10-19
1
+1
Neutron
1.675 × 10-27
0
1
0
Electron
9.109 × 10-31
1.602 × 10-19
11836
-1
Intermediate Level
Electron
Discovered by J.J. Thomson.
Charge: 1.6022 × 10-19 C
Mass: 9.1095 × 10-31 kg
Relative charge: -1
Deflected towards positive pole.
Proton
Charge: equal to electron but positive.
Mass: 1.6727 × 10-27 kg
Relative charge: +1
Deflected towards negative pole.
1836 times heavier than electron.
Neutron
No charge.
Mass: 1.6750 × 10-27 kg
Slightly more massive than proton.
Undeflected in electric and magnetic fields.
Key Comparison
Property
Electron
Proton
Neutron
Charge
Negative
Positive
Neutral
Relative charge
-1
+1
0
Mass (kg)
9.109 × 10-31
1.672 × 10-27
1.675 × 10-27
Relative mass
11836
1
1
Discovered by
J.J. Thomson
—
—
Deflection
Positive pole
Negative pole
None
Important Points
1. Electron: Negative, light, discovered by J.J. Thomson.
2. Proton: Positive, heavy, 1836 times heavier than electron.
3. Neutron: Neutral, slightly more massive than proton.
4. Electrons deflected towards positive pole.
5. Protons deflected towards negative pole.
6. Neutrons undeflected.
7. Electrons and protons are electromagnetic in nature.
8. Neutron is more massive than proton.
Remember
- Electron: Negative, light
- Proton: Positive, heavy
- Neutron: Neutral, slightly heavier than proton
- Electron mass:9.1095 × 10-31 kg
- Proton mass:1.6727 × 10-27 kg
- Neutron mass:1.6750 × 10-27 kg
Common Mistakes
1. Confusing mass of proton and neutron: Neutron is slightly more massive.
2. Forgetting the charge of electron:-1
3. Thinking neutrons are deflected in electric field: They are neutral and undeflected.
4. Mixing up the deflection directions: Electrons → positive pole; Protons → negative pole.
Quick Revision
Electron: negative, light, discovered by J.J. Thomson.
Proton: positive, heavy, 1836 times heavier than electron.
Neutron: neutral, slightly more massive than proton.
Electrons deflected towards positive pole.
Protons deflected towards negative pole.
Neutrons undeflected.
60-Second Revision
Electron: Negative, light
Proton: Positive, heavy
Neutron: Neutral, slightly heavier than proton
Electron mass:9.1095 × 10-31 kg
Proton mass:1.6727 × 10-27 kg
Neutron mass:1.6750 × 10-27 kg
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