FSc Pre-Medical Chemistry Syllabus

Who discovered the electron and by what experiment?

J. J. Thomson discovered the electron through experiments on the discharge of electricity through gases (cathode rays in a discharge tube).

What is the charge and mass of an electron?

Charge = −1.602 × 10⁻¹⁹ C; mass = 9.11 × 10⁻³¹ kg (≈ 0.000549 amu).

Who discovered the proton and through which rays?

E. Goldstein discovered the proton through positive (canal) rays produced in a discharge tube.

What is the charge and mass of a proton?

Charge = +1.602 × 10⁻¹⁹ C; mass = 1.6726 × 10⁻²⁷ kg (≈ 1.0073 amu).

Who discovered the neutron and in what year?

James Chadwick discovered the neutron in 1932, by bombarding beryllium with alpha particles.

What were the main conclusions of Rutherford's gold-foil (alpha scattering) experiment?

The atom is mostly empty space; it has a small, dense, positively charged nucleus at the centre; and electrons revolve around this nucleus.

What is the charge-to-mass ratio (e/m) of the electron?

1.7588 × 10¹¹ coulombs per kilogram, determined by J. J. Thomson.

State the main postulate of Bohr's atomic model regarding electron orbits.

Electrons revolve around the nucleus only in certain fixed, circular orbits (stationary states) of definite energy, without radiating energy.

According to Bohr, what is the condition for the angular momentum of an electron?

Angular momentum is quantized: mvr = nh/2π, where n is a positive integer (1, 2, 3...) and h is Planck's constant.

How does an electron emit or absorb energy in Bohr's model?

Energy is absorbed when an electron jumps to a higher orbit and emitted (as a photon) when it falls to a lower orbit; ΔE = E₂ − E₁ = hν.

What is the radius of the first Bohr orbit of hydrogen?

0.529 Å (0.529 × 10⁻¹⁰ m), known as the Bohr radius.

State two main defects of Bohr's atomic model.

It could not explain the spectra of multi-electron atoms or the splitting of spectral lines (Zeeman and Stark effects), and it violated Heisenberg's uncertainty principle by fixing both position and momentum.

What does the principal quantum number (n) describe?

It describes the main energy level (shell) and the size and energy of the orbital; n = 1, 2, 3, ... (K, L, M, N...).

What does the azimuthal (angular momentum) quantum number (l) describe?

It describes the subshell and the shape of the orbital; l ranges from 0 to (n−1), where l = 0,1,2,3 correspond to s, p, d, f.

What does the magnetic quantum number (m) describe, and what values can it take?

It describes the orientation of orbitals in space; m ranges from −l to +l including zero (2l+1 values).

What does the spin quantum number (s) describe?

It describes the direction of spin of an electron about its own axis; it can be +1/2 or −1/2.

How many orbitals and electrons can the s, p, d, and f subshells hold?

s: 1 orbital, 2 electrons; p: 3 orbitals, 6 electrons; d: 5 orbitals, 10 electrons; f: 7 orbitals, 14 electrons.

What is the shape of s and p orbitals?

An s orbital is spherical; a p orbital is dumb-bell shaped (with two lobes).

State the Aufbau principle.

Electrons fill orbitals in order of increasing energy, occupying the lowest-energy available orbital first before higher ones.

State the (n + l) rule for orbital energy.

Orbitals fill in order of increasing (n + l); if two orbitals have the same (n + l) value, the one with lower n is filled first (e.g. 4s before 3d).

State the Pauli exclusion principle.

No two electrons in an atom can have the same set of all four quantum numbers; an orbital holds at most two electrons with opposite spins.

State Hund's rule of maximum multiplicity.

Electrons occupy degenerate (equal-energy) orbitals singly with parallel spins first, before any orbital is doubly occupied.

Write the electronic configuration of chromium (Z = 24).

1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵ 4s¹ — a half-filled 3d gives extra stability rather than 3d⁴ 4s².

State Boyle's law.

At constant temperature, the volume of a fixed mass of gas is inversely proportional to its pressure: V ∝ 1/P, or PV = constant.

State Charles's law.

At constant pressure, the volume of a fixed mass of gas is directly proportional to its absolute (Kelvin) temperature: V ∝ T, or V/T = constant.

State Avogadro's law.

Equal volumes of all gases, under the same conditions of temperature and pressure, contain an equal number of molecules.

State Dalton's law of partial pressures.

The total pressure of a mixture of non-reacting gases equals the sum of the partial pressures of the individual gases: P_total = P₁ + P₂ + P₃ + ...

Write the ideal gas equation and define each term.

PV = nRT, where P = pressure, V = volume, n = number of moles, R = general gas constant, and T = absolute temperature.

What is the value of the general gas constant R in SI units?

R = 8.314 J K⁻¹ mol⁻¹ (also 0.0821 dm³·atm·K⁻¹·mol⁻¹).

State the key postulates of the kinetic molecular theory of gases.

Gas molecules are tiny particles in constant random motion; their actual volume is negligible compared to total volume; there are no attractive/repulsive forces between them; collisions are perfectly elastic; and average kinetic energy is directly proportional to absolute temperature.

Under what conditions do real gases deviate most from ideal behaviour, and why?

At high pressure and low temperature, because molecules are close together so their finite volume and intermolecular attractive forces become significant, violating the ideal-gas assumptions; van der Waals introduced correction terms for this.