Which species has 48 electrons

Isotopes have the same atomic number, but different mass numbers. Isotopes can either be radioactive or non-radioactive. For example, 14 C is used in radiocarbon dating to determine the age of historical objects and 99 Tc is used in medical imaging. Most hydrogen atoms consist of just one proton and one electron, but some also have one or two neutrons.

Neutrons also reside in the nucleus. In most stable nuclei, the number of neutrons approximately equals the number of protons.

As the number of protons in the nucleus increases, so does the number of neutrons. The neutrons seem to play some kind of role in stabilizing the nucleus. While a chlorine atom always has 17 protons, it can have any number of neutrons. Two atoms with the same number of protons and different number of neutrons are called isotopes. Two naturally occurring stable isotopes exist for chloride. One has 18 neutrons and the other has 20 neutrons. The two different kinds of atom are called isotopes of copper.

The neutron has a mass very similar to that of the proton, so the two isotopes differ in mass. The sum of the numbers of neutrons and protons for a particular isotope is called the mass number. The two isotopes are written, and where the mass number and atomic number precede the chemical symbol as a superscript and subscript, respectively Figure 5. The mass number of any isotope is equal to the relative atomic mass of its atom, rounded to the nearest whole number.

Thus, the relative atomic mass of natural copper But although copper contains two different isotopes, each isotope has the same atomic number, and therefore a virtually identical chemistry. As you work through this course you will need various resources to help you complete some of the activities.

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