helium has 2 protons and 2 neutrons. so its atomic number is 4
Helium
4 is the mass number of helium (mass number = number of protons + number of neutrons)
Most helium has a mass number of 4. The rare 3He isotope has a mass number of 3. The mass number is the integer total of protons and neutrons for a given isotope. For example radioactive carbon-14 has a mass number of 14, while carbon-12 (the most common stable form) has a mass number of 12.
The isotopic notation for helium-4 is ^4He. This notation denotes the element's atomic number and mass number, which for helium-4 are 2 (atomic number) and 4 (mass number) respectively.
Helium-4.
4He or He4. 4 stands for the mass number of Helium Mass number = number of protons + number of neutrons Since the atomic number or number of protons in helium is 2, the number of neutrons in He-4 is also 2.
Helium's atomic number is 2 and its atomic mass is 4
helium = 4 molar mass
Helium is a non metal element. Atomic mass number of it is 4.
If you think to tritium (hydrogen-3) the mass number is 3.If you think to helium-4 the mass number is 4.
Helium is number 2 on the Periodic Table, and the number of its mass is 4. So, therefore it has 2 protons, 2 neutrons, and 2 electrons !
Helium is lighter than air because of atomic mass. Helium is element number two, whereas oxygen is element number 8. Oxygen has an atomic mass of 16, and helium has a mass of 4, so helium is 4 times lighter than air. (Atomic mass is the total mass of protons, neutrons, and electrons in a single atom.)