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 mass $=$ number of protons $=$ number of neutrons
(iv) Atomic number $=$ number of protons $=$ number of electrons

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Important Questions on Structure Of The Atom

MEDIUM

9th CBSE

IMPORTANT

NCERT Exemplar Science - Class 9>Chapter 4 - Structure Of The Atom>Multiple Choice Questions>Q 7

In the Thomson's model of atom, which of the following statements are correct?
(i) The mass of the atom is assumed to be uniformly distributed over the atom.
(ii) The positive charge is assumed to be uniformly distributed over the atom.
(iii) The electrons are uniformly distributed in the positively charged sphere.
(iv) The electrons attract each other to stabilise the atom.

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9th CBSE

IMPORTANT

NCERT Exemplar Science - Class 9>Chapter 4 - Structure Of The Atom>Multiple Choice Questions>Q 8

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 of the above statements are correct?

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9th CBSE

IMPORTANT

NCERT Exemplar Science - Class 9>Chapter 4 - Structure Of The Atom>Multiple Choice Questions>Q 9

The ion of an element has