The nucleus of a hydrogen atom can be represented by this symbol: 1 H (i) Complete this sentence by putting a cross (X) in the box next to your answer - Edexcel - GCSE Physics - Question 6 - 2014 - Paper 1

The symbols for deuterium (( {}^{2}{1}D )) and tritium (( {}^{3}{1}T )) indicate that both are isotopes of hydrogen because they have the same atomic number (1), meaning they have the same number of protons. However, they differ in their mass numbers; deuterium has one neutron along with the proton, while tritium has two neutrons. This variation in neutron number while maintaining the same number of protons confirms that they are indeed isotopes.

A helium nucleus has a positive charge due to the presence of two protons, as represented by the charge of +2. In contrast, a neutron carries no charge, meaning it is electrically neutral. Therefore, the helium nucleus is positively charged, while the neutron has zero charge.