Explain the different types of spectral series.

When an electron in an excited state falls back to a lower energy state, it emits photon of particular energy which is equal to the difference in energies of two states. Rydberg formula gives a relation between energy difference between various energy levels and the wavelength of the photons. ν = R Z 2 1 n 1 2 - 1 n 2 2 where R is the Rydberg constant, Z is the atomic number and n 1 and n 2 are the principal quantum numbers of the orbit. The spectral lines are formed as a result of electronic transition from one energy level to another. For a hydrogen atom, these lines are divided into five series: (i) Lyman series: Lyman series is obtained when an electron jumps to the first orbit from any other outer orbit. The wavelengths of Lyman series lies in the ultraviolet region of the spectrum. (ii) Balmer series: Balmer series is obtained when an electron jumps to the second orbit from any other outer orbit. The wavelengths of Balmer series lies in the visible region of the spectrum. (iii) Paschen series: Paschen series is obtained when an electron jumps to the third orbit from any other outer orbit. The wavelengths of Paschen series lies in the infrared region of the spectrum. (iv) Brackett series: Brackett series is obtained when an electron jumps to the fourth orbit from any other outer orbit. The wavelengths of Brackett series lies in the infrared region of the spectrum. (v) Pfund series: This series is obtained when an electron jumps to the fifth orbit from any other outer orbit. The wavelengths of Pfund series lies in the infrared region of the spectrum.

A difference of 2 . 3 eV separates two energy levels in an atom. What is the frequency of radiation emitted when the atom makes a transition from the upper level to the lower level?

The Separation of two energy levels in an atom, E = 2 . 3 eV = 2 . 3 × 1 . 6 × 10 - 19 = 3 . 68 × 10 - 19 J The relation between energy and frequency is given by, E = h v Where, Planck’s constant h = 6 . 62 × 10 - 34 Js , and, ν is the frequency of radiation. ∴ ν = E ⁄ h = 3 . 68 × 10 - 19 6 . 62 × 10 - 34 = 5 . 55 × 10 14 Hz The radiation frequency is 5 . 6 × 10 14 Hz . Here, the symbols have their usual meaning.

E M B I B E

Physics Crash Course (Based on Revised Syllabus-2023)>Chapter 12 - Atoms>Exercise>Q 34

MEDIUM

12th Karnataka Board

IMPORTANT

Earn 100

Give a brief account of Thomson model of atom. What are its limitations?

Important Questions on Atoms

HARD

12th Karnataka Board

IMPORTANT

Physics Crash Course (Based on Revised Syllabus-2023)>Chapter 12 - Atoms>Exercise>Q 3

Write two limitations of Bohr's atomic model.

HARD

12th Karnataka Board

IMPORTANT

Physics Crash Course (Based on Revised Syllabus-2023)>Chapter 12 - Atoms>Exercise>Q 4

Use Bohr's postulate for permitted orbits to prove that the circumstances of the nth permitted orbit for the electron can contain exactly n wavelengths of the de Broglie wavelength associated with the electron in that orbit.

HARD

12th Karnataka Board

IMPORTANT

Physics Crash Course (Based on Revised Syllabus-2023)>Chapter 12 - Atoms>Exercise>Q 35

Discuss different atomic models and compare their merits and demerits.

EASY

12th Karnataka Board

IMPORTANT

Physics Crash Course (Based on Revised Syllabus-2023)>Chapter 12 - Atoms>Exercise>Q 39

What states of matter are responsible for the emission of band spectrum?

HARD

12th Karnataka Board

IMPORTANT

Physics Crash Course (Based on Revised Syllabus-2023)>Chapter 12 - Atoms>Exercise>Q 40

The ground state energy of hydrogen atom is $- 13.6 eV .$ If an electron makes a transition from an energy level $- 0.85 eV$ to $- 1.51 eV,$ calculate the wavelength of the spectral line emitted. To which series of hydrogen spectrum does this wavelength belong?