Protons.
The atomic number of an atom is equivalent to the number of protons in its nucleus.
Atomic number is the equivalent of the number of protons in an atomic nucleus.
The atomic number is an integer, equivalent to number of protons in the atomic nucleus.
The atomic number in a given element is equivalent to the number of protons in the element.
In a neutral atom the atomic number is the equivalent to number of electrons and protons.
The atomic number of an element is equivalent to the number of protons in its nucleus. In the case of iridium-174, the atomic number of iridium (Ir) is 77.
Either the number of protons or the number of electrons in a neutral atom is equivalent to its atomic number.
Electrons or atomic number. The atomic number is the number of protons as well as the principle quantum number.
The atomic number is equivalent to the number of protons; the number of neutrons is different for each isotope.
The number of protons is equivalent to the Atomic Number.
The atomic number of an element is based on the number of protons in its nucleus because it is equivalent to its charge number.
The atomic number is equivalent to the number of protons in the nucleus. See the Periodic Table of elements at the link below.