# Topic: Atomic Structure

2

Q:

The Bohr orbit radius for the hy drogen atom (n - 1) is
approximately 0.530Å . The radius for the first excited
state (n - 2) orbit is

(a) :  0.13Å
(b) :  1.06Å
(c) :  4.77Å
(d) :   2.12Å

Q:

The energy of an electron in the first Bohr orbit of
H atom is 13.6eV . The possible energy v alue(s) of the
excited state(s) for electrons in Bohr orbits to hy drogen
is(are)

(a) :  3.4eV
(b) :  4.2eV
(c) :  6.8eV
(d) :  6.8eV

Q:

Which of the following atoms and ions are isoelectronic i.e. hav e the same number of electrons with the neon atom

(a) :  F
(b) :  Oxy gen atom
(c) :  Mg
(d) :   N

Explanation:

F-have the same number of electrons with the neon atom.

Q:

In a Bohr's model of atom when an electron jumps from n - 1 to n - 3 , how much energy will be emitted or absorbed

(a) :  2.15 ×10^-11 erg
(b) :   0.1911× 10^-10 erg
(c) :   2.389× 10^-12 erg
(d) :  0.239× 10^-10 erg

Q:

The series limit for Balmer series of H-spectra is

(a) :  3800
(b) :   4200
(c) :   3646
(d) :   4000

Explanation:

The last line in any series is called series limit. Series limit for
Balmer series is 3646 Å.

Q:

Which of the following has maximum number of unpaired
electron (atomic number of Fe 26)

(a) :  Fe
(b) :  Fe (II)
(c) :  Fe (III)
(d) :  Fe (IV)

Explanation:

Q: (a) :  A
(b) :  B
(c) :  C
(d) :  D

Q: (a) :  A
(b) :  B
(c) :  C
(d) :  D

Q:

The ratio of the energy of a photon of 2000Å wavelength radiation to that of 4000Å radiation is

(a) :  1 /4
(b) :  4
(c) :   1 /2
(d) :  2