Answer:
Barium.
Explanation:
Each chemical element is characterized by the number of protons in its nucleus, which is called the atomic number Z. But in the nucleus of each element it is also possible to find neutrons, whose number can vary. The atomic mass (A) is obtained by adding the number of protons and neutrons in a given nucleus.
The same chemical element can be made up of different atoms, that is, their atomic numbers are the same, but the number of neutrons is different. These atoms are called isotopes of the element. Isotopes means "same place", that is, since all the isotopes of an element have the same atomic number, they occupy the same place in the Periodic Table. So if a neutron is added to an atom, it becomes an isotope of that chemical element.
The isotopes of an element have the same chemical properties, but differ somewhat in their physical properties.
Barium has an atomic number of 56 (number of protons). Also, the mass number of this barium isotope is 130 (56 protons + 76 neutrons). Finally, since it has 54 electrons, two negatively charged electrons less than the number of positively charged protons, this isotope is a cation with oxidation number +2.
