Answer: Option B. -> Positively charged particles are concentrated at the centre of the atom
:
B

When alpha particles are sent through a thin metal foil only one out of ten thousand rebounded. Rutherford concluded that positively charged particles are concentrated at the centre of the atom. At the time of the experiment, the atom was thought to be analogous to plum pudding (as proposed by J.J. Thomson), with the negative charges (the plums) found throughout a positive sphere (the pudding). If the plum pudding model were correct, the positive "pudding", being more spread out than in the current model of a concentrated nucleus, would not be able to exert such large Coulombic forces, and the alpha particles should only be deflected by small angles as they pass through.

Answer: Option A. -> Gold
:
A
In the alpha-ray experiment, Rutherford preferred gold over other metals because it is the most malleable metal. The gold sheet used by Rutherford was about 1000 atoms thick.

Answer: Option C. -> 2, 8, 1
:
C

Atomic number of sodium is 11. Thus, it contains 11 protons.
For a neutral atom, the number of  protons is equal to the number of electrons. Hence, for sodium atom, the number of electrons = 11.
The maximum no. of electrons that can be accommodated in a shell is given by $2\times n^2$, where n represents the no. of shell.
Hence, no. of electrons in 
K shell = ($2\times 1^2$) = 2 electrons
L shell = ($2\times 2^2$) = 8 electrons 
Now only one electron is remaining. Thus, M shell accomodates 1 electron.

Hence, electronic configuration of sodium atom is 2, 8, 1.

Answer: Option C. -> Neutral
:
C
An atom has always an equal number of electrons (negatively charged particles) and protons (positively charged particles), because of which there is no charge on the atom. Neutrons being neutral does not affect the charge of an atom.

Answer: Option C. -> John Dalton
:
A, B, and D
John Dalton has only proposed the atomic theory of atoms. He said that atoms are indivisible. Through the other models, we can understand that atoms have particles inside it and can be divisible. So, his theory was proved wrong.
J.J. Thomson proposed the plum pudding model of an atom which has electrons randomly placed in an atom resembling a spherical christmas pudding.
Rutherford introduced an atomic model with positively charged nucleus and electrons revolving around it in circular path.
Niels Bohr put forward the concept of discrete orbits in which electrons are allowed to revolve around. 

Answer: Option B. -> False
:
B
The radioactivity has medical and industrial applications as well. An isotope of uranium is used as a fuel in nuclear reactors. An isotope of cobalt is used in the treatment of cancer. Hence the given statement is false.

Answer: Option C. -> E.Rutherford
:
C

E. Rutherford is regarded as the father of nuclear physics.

Answer: Option B. -> False
:
B
Niels Bohr put forward that electrons while revolving in discrete orbits do not radiate energy as long as they are in discrete energy shells. This is how he explained the stability of atoms which Thomson and Rutherford failed to prove. 

Answer: Option B. -> Alpha particles are positively charged species.
:
B and C
Alpha particles are identical to helium nucleus. When electrons are removed from helium atom, only two protons are left in its nucleus which makes it positively charged. In Rutherford's experiment, the alpha particles are repelled by the nucleus. This shows that alpha particles are positively charged.

Answer: Option B. -> They are electrically neutral.
:
B
Gamma rays are electromagnetic radiations. They are electrically neutral in nature. They have no mass.