Why are the symbols ⁷⁹₃₅Br,  and ⁷⁹Br are considered acceptable, whereas  ³⁵₇₉Br and ³⁵Br are not acceptable representations of bromine?

Which of the following gives the atomic numbers of the elements having outermost electronic configurations 3s¹ and 2p⁵, respectively?

Calculate the number of electrons corresponding to a charge of 2.5 × 10⁻¹⁶ C.

How many carbon atoms of diameter 0.15 nm can be placed side by side to form a straight line of length 20 cm?$\mathrm{}$

What is the number of zinc atoms present in a linear arrangement of length 1.6 cm, given that the diameter of a zinc atom is 2.6 Å?

Find the radius of each carbon atom if 2 × 10⁸ identical carbon atoms arranged side by side form a straight line of length 2.4 cm.

1. 7.0 × 10^–11 m

2. 5.0 × 10^–11 m

3. 8.0 × 10^–11 m

4. 6.0 × 10^–11 m

The wavelength of yellow light emitted by a sodium lamp is 580 nm. Calculate its frequency and wave number, respectively.

1. 517 × 10¹⁴ s^–1 , 172 × 10⁶ m^–1

2. 6.17 × 10¹⁴ s^–1 , 1.72 × 10⁶ m^–1

3. 4.17 × 10¹⁴ s^–1 , 2.72 × 10⁶ m^–1

4. 5.17 × 10¹⁴ s^–1 , 1.72 × 10⁶ m^–1

Calculate the wave number of light having a time period of 2.0 × 10⁻¹⁰ s. 

1. 16.66 m^–1

2. 1.66 m^–1

3. 32.34 m^–1

4. 12.34 m^–1