worksheet on structure of an atom class 9

Rutherford’s alpha (α) particles scattering experiment resulted in the discovery of:

(a) electrons (b) protons (c) the nucleus in the atom (d) atomic mass

Which of the following are true for an element?

(I) Atomic number = number of protons + number of electrons

(II) Mass number = number of protons + number of neutrons

(III) Atomic number = number of protons + number of neutrons

(IV) Atomic number = number of protons

Options: (a) (I) and (II)

(b) (I) and (III)

(c) (II) and (III)

(d) (II) and (IV)

If an atom of an element has 11 protons and 12 neutrons, what will be the valency?

(a) 2 (b) 3 (c) 1 (d) 4

Which isotope is used in the treatment of goitre?

(a) Uranium-235 (b) Iodine-131 (c) Cobalt-60

. Rutherford’s α-particle scattering experiment showed that:

(I) Electrons have negative charge.

(II) The mass and positive charge of the atom is concentrated in the nucleus

. (III) Neutron exists in the nucleus.

(IV) Most of the space in atom is empty

. Which one of the elements does NOT show electrovalency?

(a) Sodium (b) Oxygen (c) Chlorine (d) Carbon

Which subatomic particle is responsible for the chemical properties of an element?”

(a) Proton (b) Electron (c) Neutron (d) Nucleus

. Octet electrons mean:

(a) two electrons in the outermost shell