The number of protons is identical.
Different Isotopes of the same element will each exhibit the same Chemical Characteristics.
The same numbers of protons and of electrons; the difference between isotopes is in the number of neutrons.
Two different neutral isotopes of the same element have the same number of protons in their nucleus, which determines the element's identity. The isotopes differ in the number of neutrons they have, which leads to variations in atomic mass but not in chemical properties.
They have the same number of protons and electrons.
The number of protons and electrons is the same.
They have the same numbers of electrons and protons.
The proton and electron number are equal for all isotopes of the same specific element.
The atomic number is the same for all isotopes.
They have the same number of protons in the nucleus and same number of electrons surrounding the nucleus.
They have the same number of protons in the nucleus and same number of electrons surrounding the nucleus.
You have not told us what element "this" element is.
The isotopes 252Cf and 251Cf.