Match the following:

$A$. Chadwick	$1$. Cathode rays
$B$. Rutherford	$2$. $X$-ray spectra
$C$. Moseley	$3$. Discovery of neutrons
$D$. $J$. $J$. Thomson	$4$. Nuclear atom model

Which particle leaves no track in a Wilson cloud chamber?

Cathode rays are

Fill in the blanks:
$(i)$ For the discovery of neutrons,$\alpha$-particles were bombarded on a thin sheet of ......... .
$(ii)$ For the $\alpha$-particle scattering experiment,Rutherford used a gold foil of thickness ......... .
$(iii)$ The radius of an atom is approximately ......... and the radius of the nucleus is ......... .
$(iv)$ The entire positive charge of an atom is concentrated in a very small region,which is called ......... .

What are cathode rays?

Which of the following particles cannot be accelerated by an electric or magnetic field?