AP Inter 2nd Year Physics Notes Chapter 13 Atoms

Students can go through AP Inter 2nd Year Physics Notes 13th Lesson Atoms will help students in revising the entire concepts quickly.

AP Inter 2nd Year Physics Notes 13th Lesson Atoms

→ J-J-Thomson proposed a structure for the atom.

→ Rutherford and then Niel Bohr modified the structure of atom proposed by Thomson.

→ Rutherford α – particle scattering experiment established the existence of nucleus.

→ The distance of closest approach, gives an estimate of the size of the nucleus.

→ Rutherford’s atom model could not explain the stability of the atom and the line spectrum of atoms.

→ Bohr suggested a new model of atoms to account for the stability of the atom and emission of line spectra by the atoms.

→ Bohr postulated that the electrons can revolve only in certain non-radiating orbits for which mvr = \(\frac{\mathrm{nh}}{2 \pi}\)

→ Non-radiating orbits are called stationary orbits.

→ Stationary orbits of electrons are not equally spaced.

→ The radius of first orbit of hydrogen atom is called Bohr’s radius.

→ The total energy of an electron in an orbit is equal to the negative of the K.E in that orbit.

→ Ionisatom potential for a given element is fixed but for different elements, Ionisation potentials are different.

→ Ionisation potential of H-atom = 13.6 V.

→ Impact parameter of the α – particle is defined as the -⊥^r distance of the velocity vector of the α – particle from the centre of the nucleus, when it is far away from the atom.

→ Wave number is the number of complete waves in unit length.

→ Ground states is defined as the energy state of electron corresponding to n = 1.

→ The energy states of electrons corresponding*to n = 2, 3…. are called excited states.

→ Excitation energy required, so as to raise an electron from its ground state to an excited state.

→ Ionisation is the process of knocking an electron out of the atom.

→ Ionisation energy is defined as the energy required to knock an electron completely out of the atom.

Formulae

→ Distance of closest approach
r₀ = \(\frac{1}{4 \pi \varepsilon_0} \times \frac{Z e^2}{\frac{1}{2} m v^2}\)

→ Impact parameter
b = \(\frac{1}{4 \pi \varepsilon_0} \times \frac{Z e^2 \cot \theta / 2}{\frac{1}{2} m v^2}\)

→ Bohr’s quantisation condition mvr = \(\frac{\mathrm{nh}}{2 \pi}\)

→ Bohr’s frequency conditon hv = E_i – E_f

→ Radius of Bohr’s n^th orbit is
r_n = 4πε₀ \(\frac{n^2 h^2}{4 \pi^2 m e^2}\)

→ Speed of an electron revolving n^th orbit is given by υ_n = \(\frac{1}{4 \pi \varepsilon_0} \frac{2 \pi \mathrm{e}^2}{\mathrm{nh}}\)

→ Rydberg constant
R_H = \(\left(\frac{1}{4 \pi \varepsilon_0}\right)^2 \frac{2 \pi^2 \mathrm{me}^4}{\mathrm{ch}^3}\)

→ Energy of electron in n^th orbit,
E_n = \(-\left(\frac{1}{4 \pi \varepsilon_0}\right)^2 \frac{2 \pi^2 \mathrm{me}^4}{\mathrm{n}^2 \mathrm{~h}^2}\)

→ Energy of radiation emitted
E = \(\left(\frac{1}{4 \pi \varepsilon_0}\right)^2 \frac{2 \pi^2 \mathrm{me}^4}{\mathrm{~h}^2} \frac{1}{\mathrm{n}_{\mathrm{f}}^2}-\frac{1}{\mathrm{n}_{\mathrm{i}}^2}\)

→ Ionisation potential = \(\frac{\text { Ionisation energy }}{\mathrm{e}}\)