What are the three fundamental subatomic particles?

Atoms are composed of three main subatomic particles:

1. Electron (e^-) 

2. Proton (p⁺) 

3. Neutron (n^o) 

Who discovered the electron and how?

How did J.J. Thomson determine the charge-to-mass ratio of an electron?

J.J. Thomson used electric and magnetic fields in a  Cathode Ray Tube experiment to determine e/m ratio:

e/m = 1.7588820 × 10¹¹ C/kg
This means the electron has a very small mass compared to its charge.

Who determined the charge of an electron and how?

Who discovered protons and neutrons?

Proton (p⁺): Ernest Rutherford (1919) through Gold Foil Experiment.

Neutron (n^o): James Chadwick (1932) by bombarding beryllium with alpha particles.

What is Thomson’s "Plum Pudding" model?

Proposed by J.J. Thomson (1898), the atom was seen as a positively charged sphere with embedded electrons, like ‘plums in pudding’.
It failed to explain atomic structure and was later disproved by Rutherford’s experiment.

What was Rutherford’s Gold Foil Experiment and its conclusions?

Rutherford bombarded a thin gold foil with alpha particles (He²⁺ ions). He concluded:

• Atom has a dense, positive nucleus.
• Electrons revolve in orbits around the nucleus.
• The model could not explain atomic stability (why electrons don’t fall into the nucleus).

How did Bohr’s atomic model improve Rutherford’s model?

Niels Bohr (1913) proposed that:

• Electrons orbit the nucleus in fixed energy levels (orbits).
• Electrons absorb or emit energy when jumping between energy levels.
• Electrons do not spiral into the nucleus because their energy is quantized.
• Bohr’s model explained hydrogen spectra but failed for larger atoms.

What is the speed of light equation?

c = λv
Where:

• c = speed of light (3.0 × 10⁸ m/s)
• λ (lambda) = wavelength (m)
• ν (nu) = frequency (Hz)

What is Planck’s Quantum Theory?

Max Planck (1900) proposed that energy is quantized:

E = hv
Where:

• E = Energy of photon
• h = Planck’s constant (6.626 × 10^-34 J·s)
• ν = Frequency of radiation

What is Einstein’s photoelectric equation?

Albert Einstein explained the Photoelectric Effect using quantum theory:

KE = hv - hv_o 
Where:

• KE = Kinetic energy of ejected electron
• hν = Energy of incident photon
• hν_o = Work function (minimum energy required to eject electrons)

What are the four quantum numbers?

1. Principal Quantum Number (n): Energy level (n = 1, 2, 3, ...)

2. Azimuthal Quantum Number (l): Shape of orbital (s = 0, p = 1, d = 2, f = 3)

3. Magnetic Quantum Number (m₁): Orientation of orbital (-l to +l)

4. Spin Quantum Number (m_S): Electron spin (+1/2 or -1/2)

What is Heisenberg’s Uncertainty Principle?

It is impossible to know both position and momentum of an electron simultaneously:

Δx.Δp ≥ h/4π
Where:

• Δx = uncertainty in position
• Δp = uncertainty in momentum

What is the Bohr radius equation?

r_n = n² × 52.9 pm

• n = energy level
• Bohr radius = 52.9 pm (for n = 1)

What is the Rydberg equation for hydrogen spectrum?

Where:

• R_H = Rydberg constant (1.097 × 10⁷ m^-1)
• n₁, n₂ = initial and final energy levels