Question

Analyse the following figure showing transitions of electrons in the hydrogen atom.

a) Name the series (a), (b), (c), (d) and (e). 

b) Mention the region of the spectrum in which each series belongs to. 

c) Explain how they are obtained.

d) Calculate the wave length of the first line of series (b).

[R_H = 109677 cm^-1]

Answer 1

(a) = Lyman series, 

(b) = Balmer series, 

(c) = Paschen series, 

(d) = Brackett series, 

(e) = Pfund series 

(b) Lyman series – UV region 

Balmer series – Visible region 

Paschen series – Infrared region 

Brackett series – Infrared region 

Pfund series – Infrared region

(c) In hydrogen atom there is one electron which is present in first orbit in ground state. When energy is supplied this electron may be excited to some higher energy level. Since in a sample of hydrogen there are large number of atoms, the electrons in different atoms absorb different amounts of energies and are excited to different higher energy levels. Now, from excited states, the electron may return to ground state in one or more jumps. These different downward jumps are associated with different amounts of energies and hence result in the emission of radiations of different wavelengths which appear as different lines in the hydrogen spectrum. Series – Obtained when electron jumps from any of the higher energy levels to 

Lyman series – 1^st energy level 

Balmer series – 2^nd energy level 

Paschen series – 3^rd energy level

Brackett series – 4^th energy level 

Pfund series – 5^th energy level

(d) n₁ = 2, n₂ = 3, R_H = 109677 cm^-1