641.

Atomic number of an element is equal to the number of :

• protons

• neutrons

• electrons

• protons + neutrons

Radioactive isotope of hydrogen is :

• Uranium

• Deuterium

• Tritium

• None

Electronk configuration of hydride ion is :

• 1s^o

• 1s¹

• 1s²

• 1s¹2s¹

The de Broglie wavelength associated with a ball of mass 1kg having kinetic energy 0.5 J is

• 6.626 $\times$ 10^-34 m.

• 13.20 $\times$ 10^-34 m.

• 10.38 $\times$ 10^-21m.

• 6.626 $\times$10^-34$\stackrel{°}{\mathrm{A}}$.

Wave nature of electrons was demonstrated by :

• Schrodinger

• De-Broglie

• Davisson and Garmer

• Heisenberg

${}_{92}{}^{238}\mathrm{U}$ emits 8 α-particles and 6 β-particles. The neutron/proton ratio in the product nucleus is

• 60/41

• 61/40

• 62/41

• 61/42

The isoelectronic pair is

• Cl₂O, ICl₂^-

• ICl₂^-, ClO₂

• IF₂⁺, I₃^-

• ClO₂^-, ClF₂⁺

α-Particles can be detected using

• thin aluminium sheet

• barium sulphate

• zinc sulphide screen

• gold foil

The most probable radius (in pm) for finding the electron in He⁺ is

• 0.0

• 52.9

• 26.5

• 105.8

How many neutrons are there in nucleus 'X', if it gives ₇N¹⁴ after two successive $\mathrm{\beta }$ - particle emissions ?

• 7

• 10

• 14

• 09