141.

Neutrons are found in atoms of all elements except in

• chlorine

• oxygen

• argon

• hydrogen

The atomic weight of an element is 39. The number of neutrons in its nucleus is one more than the number of protons. The number of protons, neutrons and electrons-respectively in its atoms would be

• 19, 20, 19

• 19, 19, 20

• 20, 19, 19

• 20, 19, 20

The energy and radius of electron present in second orbit of He⁺ respectively are

• -109 × 10^-18J, 105.8 pm

• -872 × 10^-18 J, 211.6 pm

• -4.36 × 10^-18 J, 52.9 pm

• -2.18 × 10^-18 J, 105.8 pm

Assertion (A): Na⁺ and Mg²⁺ ions are isoelectronic but the ionic radius of Na⁺ is greater than that of Mg²⁺.

Reason (R): The effective nuclear charge of Na⁺ ion is less than that of Mg²⁺ ion.

• Both (A) and (R) are correct but (R) is not the correct explanation of (A)

• Both (A) and (R) are correct and (R) is correct explanation of (A).

• (A) is not correct but (R) is correct.

• (A) is correct but (R) is not correct.

The work functions of Ag, Mg, K and Na respectively in eV are 4.3, 3.7, 2.25, 2.30. When an electromagnetic radiation of wavelength of 300 nm is allowed to fall on these metal surface, the number of metals from which the electrons are ejected is (1eV = 1.6022 × 10^-19 J).

• 4

• 3

• 2

• 5

For n = 3 energy level, the number of possible orbitals (all kinds) are

• 1

• 3

• 4

• 9

In 1 mole of NaCl the proton are

• 6 moles

• 11 moles

• 17 moles

• 28 moles

The values for all the quantum numbers for 15^th electron of chlorine are

• n = 3; l = 1; m = 0; s = -$\frac{1}{2}$

• n = 4; l = 2; m = 0; s = + $\frac{1}{2}$

• n = 3; l = 1; m = +1; s = +$\frac{1}{2}$

• n = 2; l = 0; m = 0; s = +$\frac{1}{2}$

For which of the following species, Bohr theory does not apply?

• H

• He⁺

• H⁺

• Li²⁺

Which of the following is incorrect for radial distribution curve?

• n = 2; l = 0; Node = 1

• n = 3; l = 0; Node = 2

• n = 2; l = 1; Node = 0

• n = 3; l = 2; Node = 1