Which statement is incorrect about electrons ?

1. Electron is a negatively charged particle.
2. Its mass is equal to the mass of neutron.
3. It is a constituent of cathode rays.
4. It is a basic constituent of all atoms.

Two atoms are said to be isobars if they have the same:

1. number of neutrons but different number of electrons.
2. number of electrons but different number of neutrons.
3. atomic number but different mass numbers.
4. sum of protons and neutrons but the number of protons is different.

Postulates of modern atomic theory are:

P — Atoms of an elements may not be alike.

Q — Atoms of elements combine in small whole numbers to form molecules.

R — Atoms can neither be created nor destroyed.

1. Only P
2. Only Q
3. Only R
4. Both P and Q

An atom is electrically neutral because :

P — Electrons, protons and neutrons are equal in number.

Q — Protons are equal to neutrons.

R — Protons are equal to electrons.

1. Only P
2. Only Q
3. Only R
4. Both Q and R