Final answer:
The atomic symbol for helium is He, with helium-4's nuclear symbol being 4He2, indicating 2 protons and 2 neutrons in the nucleus.
Step-by-step explanation:
The atomic symbol for helium is He. The atomic symbol combines the chemical symbol with the atomic number and the mass number. For helium, the most common isotope has an atomic number of 2 and a mass number of 4, indicating that there are two protons and two neutrons in the nucleus. The nuclear symbol for helium-4 is written with the mass number as a superscript to the top left of the symbol (4), and the atomic number as a subscript to the bottom left of the symbol (2). Therefore, the full representation of the nuclear symbol for helium is written as 4He2. When discussing alpha-particles, the same symbol can be used because they are essentially helium nuclei.