Give the full symbol for the atom or ion that has eight protons and eight neutrons in its nucleus, and ten electrons outside the nucleus. Also give the name of the group this element is located in.

Understanding the atomic number is crucial for identifying elements and their properties. The atomic number, represented by the symbol 'Z', is the number of protons found in the nucleus of an atom. It defines the element's identity, as each element has a unique atomic number. In our exercise, the atomic number is 8, which corresponds to oxygen. Since the number of protons determines the atomic number, it is the same for both neutral atoms and ions of that element. Remember, while an ion may gain or lose electrons, the number of protons (and thus the atomic number) remains unchanged.

The periodic table is a tabular arrangement of all known elements, ordered by increasing atomic number. It is a powerful tool for predicting the properties of elements and how they interact with each other. Elements with similar physical and chemical properties are grouped together in columns known as 'element groups'. Oxygen, with an atomic number of 8, is found in the p-block of the periodic table, which consists of groups 13 to 18. The table also shows periods (rows), which indicate elements with the same number of electron shells. By using the periodic table, we can locate oxygen in Group 16, which tells us about its reactivity and other chemical behavior.

The atomic mass number, denoted as 'A', is the total number of protons and neutrons in an atom's nucleus. Unlike the atomic number, the mass number can vary, resulting in different isotopes of an element. However, this mass number does not change an element's fundamental identity; rather, it affects isotopic mass and stability. In the given exercise, we have an oxygen ion with 8 protons and 8 neutrons, making the atomic mass number 16. When describing an ion or isotope, the atomic mass number is placed as a superscript before the element symbol, while the atomic number is placed as a subscript before it. So, for the oxygen ion in our example, the notation is \(O^{16}_{8}\), which conveys vital information about its nuclear composition.

Element groups, also known as families, are columns within the periodic table that gather elements with similar properties and trends in chemical behavior. For instance, oxygen is in Group 16, which is also known as the Chalcogens. Members of this group have six valence electrons, which significantly influences their tendency to form compounds by gaining or sharing two additional electrons to achieve a stable octet configuration. Group 16 elements are diverse, including nonmetals (like oxygen), metalloids, and metals. Learning about an element's group can provide insights into its reactivity, common oxidation states, and the types of chemical bonds it can form.