Atoms and nuclear energy — GCSE Physics practice questions

Question 1

An α-particle is a helium nucleus. It is made of 2 protons and 2 neutrons.

What is the relative charge of an α-particle?

Accepted Answer

C: +2. A proton has a relative charge of +1 and a neutron has no charge. The α-particle has 2 protons and 2 neutrons and no electrons, so its relative charge is 2 × (+1) + 2 × 0 = +2.

Question 2

A student uses a tablet simulation of α-particles fired at a very thin sheet of platinum. The screen zooms in on two platinum nuclei and shows the paths of five α-particles, numbered 1 to 5.

Which row gives a correct conclusion from each set of paths?

Accepted Answer

A: most of the atom is empty space · the nucleus is positive and has a large mass. Paths 1, 3 and 5 pass well away from the nuclei and hardly change direction, so most of the space inside the atom is empty. Path 2 heads almost straight at a nucleus and is turned back: the nucleus must repel the positive α-particle, so it is positive, and it must be much more massive than the α-particle.

Question 3

One way in which a uranium-235 nucleus can split is shown by the equation

23592U + 10n → 14055Cs + X + 2 10n

Which symbol represents nucleus X?

Accepted Answer

C: ⁹⁴₃₇Rb. Nucleon numbers: 235 + 1 = 236 on the left, so X has 236 − 140 − 2 = 94. Proton numbers: 92 + 0 = 92, so X has 92 − 55 = 37, which is rubidium. X is ⁹⁴₃₇Rb.

	paths 1, 3 and 5 show that	path 2 shows that
A	most of the atom is empty space	the nucleus is positive and has a large mass
B	the nucleus is positive and has a large mass	most of the atom is empty space
C	most of the atom is empty space	the α-particle bounced off an electron
D	the atom contains electrons	the nucleus contains neutrons