Question

State reasons for E. Rutherford to choose α - particle for scattering, and a gold foil as a target in his α - ray scattering experiment. Explain.

Points : 10 ☺

Answer 1

he selected gold foil because he wanted as thin as layer possible ....a particles r doubled charged helium ions..since theu have mass of 4u  the fast moving a particles have a considerable amount of energy....he expected that a aparticles would be deflected by the subatomic particles in the gold atom....since..the a particles were uch heavier than the protons he did not expect to see large deflections...in his experiment he saw that most of the fast moving a particles passed straight through the gold foil...some a particles were deflected....n some appeared to rebound....to study the size of the nucleus as bcoz an electron will be deflected by all of the electrons in the gold foil as well as the nucleus whereas an alpha particle plows through thethe electrons n only deflected by nucleus 

Answer 2

Rutherford scattering experiment :- Rutherford use alpha particle in scattering experiment due to

1) alpha particles are unstable particle posses speeds of the order of 10^7 m/sec and they travel several centimeters through air ,or on the order of 0.1mm through solid matter , before they are brought to rest by collisions.

2) alpha particles are also heavy massive particle , penetrating without any obstacles freely .

NOTE :- alpha particle is positive He nuclei .
e.g. He+2

why use gold foil in this experiment ?

ans :- we know, gold is a metal which is generally stable reaction with any acid ( only acqua razia is fit for reaction of gold )
and it's high tensile property , we easily convert minimum width e.g 0.1 mm .
for this reason Rutherford preferred gold foils. ,i think.