the number of protons in the nucleus of an atom is called the....

atomic number

That's correct! The number of protons in the nucleus of an atom is called the atomic number. The atomic number uniquely identifies each element on the periodic table. To find the atomic number of an atom, you can refer to the element's position on the periodic table or search for it in any reliable source such as a chemistry textbook or website. The atomic number is usually displayed as a whole number above or before the element's symbol. For example, the atomic number of hydrogen is 1, while the atomic number of carbon is 6.