Question

Match the names of the Scientists given in column A with their contributions towards the understanding of the atomic structure as given in column B (A) – (B) (a) Ernest Rutherford – (i) Indivisibility of atoms (b) J.J.Thomson – (ii) Stationary orbits (c) Dalton – (iii) Concept of the nucleus (d) Neils Bohr – (iv) Discovery of electrons (e) James Chadwick -(v) Atomic number (f) E. Goldstein – (vi) Neutron (g) Mosley – (vii) Canal rays

Column 1	Column 2
A) Ernest Rutherford	1) Indivisibilty of atoms
B) J.J thomson	2) Stationary orbits
C) Dalton	3) Concept of Nucleus
D) Neils Bohr	4) Discovery of electrons
E) James Chadwick	5) Atomic number
F) E. Goldstein	6) Neutron
G) Mosley	7) Canal rays

Answer 1

A. Ernest Rutherford- 3. Concept of Nucleus

1. Ernest Rutherford found that the atom is nearly empty space with all of its mass concentrated at the nucleus.
2. The Nucleus is positively charged and surrounded by negatively charged electrons.

B. J.J Thomson- 4.Discovery of Electrons

1. J.J Thomson experiments with cathode ray tubes showed that all atom is made up of tiny negatively charged particles called as Electrons.
2. He proposed plum pudding model in which negatively charged particles is embedded over positive charged soup.

C. Dalton- 1. Indivisibility of Atom

1. Dalton proposed that matter is made up of tiny indivisible particles called as Atoms.
2. He imagined atom as a Solid, massy, hard and impenetrable movable particles.

D. Neils Bohr- 2.Stationary orbits

1. Bohr proposed that electrons do not radiate energy as they orbit the nucleus, but exist in states of constant energy called stationary states.
2. Stationary states means electrons are at fixed distance from Nucleus.

E. James Chadwick- 6.Neutron

1. Chadwick measured how the new radiation impacted the atoms of various gases.
2. He found that new radiation not consists of gamma rays, but the uncharged particles with the same mass as that of proton, these particles were Neutrons.

F. E.Goldstein- 7. Canal Rays

1. When an electron is removed from hydrogen atom a proton remains, Goldstein observed that rays travelling in the opposite direction of cathode rays in a cathode ray tube.
2. He demonstrated that these were positively charged particles called as Canal rays.

G. Mosley- 5. Atomic Number

1. In 1913, Mosley observe and measure the X-ray spectra of various chemical elements discovered from crystals.
2. He concluded that atomic number is the number of positive charges in the nucleus.