Chemistry : Structure of Atom

The electrons identified by quantum numbers n and l:
(a) n = 4, l = 1 (b) n = 4, l = 0 (c) n = 3, l = 2 (d) n = 3 , l = 1
Can be placed in order of increasing energy as

• (c) < (d) < (b) < (a) 

• (d) < (b) < (c) < (a)

• (b) < (d) < (a) < (c)

• (b) < (d) < (a) < (c)

A gas absorbs a photon of 355 nm and emits at two wavelengths. If one of the emission is at 680 nm, the other is at

• 1035 nm

• 325 nm

• 743 nm 

• 743 nm 

The ionization energy of He+ is 19.6 x 10–18 J atom^–1. The energy of the first stationary state (n = 1) of Li²⁺ is

• 4.41 x 10^-16 J atom^–1

• -4.41 x 10^-17 J atom^–1

• -2.2 x 10^-15 J atom^–1.

• -2.2 x 10^-15 J atom^–1.

The radius of the second Bohr orbit for the hydrogen atom is :
(Plank's const. h = 6.6262 × 10^–34 Js ; mass of electron = 9.1091 × 10–31 kg ; charge of electron
e = 1.60210 × 10^–19 C ; permittivity of vacuum
∈0 = 8.854185 × 10^–12 kg^–1 m^–3 A2)

• 1.65Å

• 4.76Å

• 0.529Å

• 0.529Å

Calculate the wavelength (in nanometer) associated with a proton moving at 1.0 × 10³ ms^–1
(Mass of proton = 1.67 × 10^–27 kg and h = 6.63 ×10^–34Js)

• 0.032 nm

• 0.40 nm

• 2.5 nm

• 2.5 nm

In an atom, an electron is moving with a speed of 600m/s with an accuracy of 0.005%. Certainty with which the position of the electron can be located is ( h = 6.6 x10^-34 kgm2s^-1 mass of electron, em= 9.1 x10^-31kg)

• 1.52 x 10^-4m

• 5.10 x 10^-3m

• 1.92 x 10^-3m

• 1.92 x 10^-3m

The ionization enthalpy of a hydrogen atom is 1.312 × 10⁶Jmol⁻¹. The energy required to excite the electron in the atom from n = 1 to n = 2 is 

• 8.51 × 10⁵ Jmol−1

• 6.56 × 10⁵ Jmol⁻¹

• 7.56 × 10⁵ Jmol⁻¹

• 7.56 × 10⁵ Jmol⁻¹

Which of the following sets of quantum numbers represents the highest energy of an atom?

• n = 3, l = 1, m = 1, s = +½

• n = 3, l = 2, m = 1, s = +½

• n = 4, l = 0, m = 0, s = +½

• n = 4, l = 0, m = 0, s = +½

According to Bohr’s theory, the angular momentum of an electron in 5th orbit is

• 25h/ π

• 1.0h/π

• 10/π

• 10/π

Uncertainty in the position of an electron (mass = 9.1 × 10^–31 kg) moving with a velocity 300 ms–1, accurate upto 0.001%, will be

• 19.2 × 10^–2 m

• 5.76 × 10^–2 m

• 1.92 × 10^–2 m

• 1.92 × 10^–2 m