The number of protons it has.
The number of protons in an atom of an element is equal to the number of electrons in that atom which is equal to that element's atomic number.
An isotope shares the atomic number with its element atom. How does it differ from the element atom?
The Atomic Number of an element is the same as the number of protons in the nucleus of an atom of that element and/or the number of electrons a in neutral atom of that element.
In an atom, the number of protons is the same number as the atomic number.
It is equal to the no. of electrons in the atom. It is called the atomic number.
Each element has a unique number of protons. If another atom has the same number of protons as that element, it is the same element.
The atomic number is an indication of the number of PROTONS in the nucleus of the atom of an element.
the number of protons
Each atom of an element has the same number of protons which is unique for that particular element ( = atom number in the periodic system)
The atomic number is the number of protons in the nucleus of an atom of an element. An element that is in its neutral state has the same number of protons and electrons, thus the atomic number can also be used to tell the number of electrons in a non-ionic atom of that element.
Mass Number
Because an atom of element has the same number of electrons as of protons and the number of protons in an atom is the same as the atomic number of the atom, the answer to this is whichever element has the highest atomic number yet synthesized.