Here students can locate TS Inter 1st Year Chemistry Notes 1st Lesson Atomic Structure to prepare for their exam.

## TS Inter 1st Year Chemistry Notes 1st Lesson Atomic Structure

→ The radiation which is made up of electrical and magnetic fields acting mutually perpendicular to each other is called Electro-magnetic radiation.

→ The number of waves that pass a point in the path of propagation of wave per second is called frequency. It is denoted by υ.

→ The number of waves present in a distance of 1 cm is called wave number. It is the reciprocal of wavelength (i.e.,) υ̅ = 1/λ.

→ According to Planck’s quantum theory emission or absorption of energy takes place in the form of small packets called Quanta. The energy of each quantum of radiation is given by E = hυ.

→ According to Einstein, both emission and absorption of radiation takes place in the form of photons. A photon is a wave particle which has no mass but has energy. The energy of a photon is given by E = hυ.

→ The emission spectrum of hydrogen consists of Lyman series, Balmer series, Paschen series, Bracket series and Pfund series.

→ According to Bohr, electrons revolve around the nucleus in certain definite circular paths, called orbits or energy levels or shells. They are denoted by the letter n.

→ Principal quantum number describes the size of the orbit and energy of the electron.

→ Azimuthal quantum number denotes the shape of the orbital.

→ Magnetic quantum number denotes the special orientation of the orbital.

→ Spin quantum number describes the direction of rotation of the revolving electron.

Its value is + 1/2 for a clockwise electron and – 1/2 for an electron revolving in the anti-clockwise direction.

→ Wave nature of electron was proposed by de Broglie.

→ According to Heisenberg’s uncertainty principle, it is not possible to determine the position and the velocity of a moving particle like electron, simultaneously and accurately.

→ Ψ is known as wave function and Ψ^{2} is known as probability function.

→ Orbital is the space around the nucleus where the probability of finding the electron is maximum.

→ Orbitals of equal energy are called degenerate orbitals.

→ Arrangement of electrons in space around the nucleus in an atom is known as electronic configuration.

→ According to Pauli’s exclusion principle, an orbital can hold a maximum of two electrons only and a shell can hold a maximum of 2n electrons.

→ Atoms or ions with paired up electron spins * are diamagnetic and with unpaired electron spins are paramagnetic.

→ Atoms or ions with the same electronic configuration are said to be iso-electronic.

→ The wave number u of the spectral lines is given by Rydberg expression,

υ̅ = \(\frac{1}{\lambda}\) = R_{H}\(\left(\frac{1}{n_1^2}-\frac{1}{n_2^2}\right)\)

→ Value of Rydberg constant

(R_{H}) = 109,677 cm^{-1}.

→ Energy of photon, E = hυ.

→ Energy of a photoelectron,

E = hυ = hυ_{0} + K.E,

where υ_{0} = threshold frequency.

→ Mass of an electron, m = 9.1 × 10^{-28} g.

→ Charge of an electron, e =-4.802 × 10^{-10} e.s.u.

→ Radius of nth orbit

(r_{n}) = 0.529 × 10^{-8} n^{2}cm.

→ Radius of Bohr’s orbit

(r) = 0.529 × 10^{-8} cm = 0.529 Å.

→ Energy of electron in the nth orbit,

(E_{n}) = \(-\frac{13.6}{n^2}\)eV

→ Value of Rydberg constant (R) = \(\frac{2 \pi^2 \mathrm{me}^4}{\mathrm{ch}^3}\)

→ de Broglie wavelength, λ = \(\frac{\mathrm{h}}{\mathrm{mV}}\).