What is the symbol of an ion with 16 protons, 18 neutrons, and 18 electrons? What is the symbol for an ion that has 16 protons, 16 neutrons, and 18 electrons?

Understanding the atomic number is crucial to identifying any element in the periodic table. It is denoted usually by the letter 'Z' and represents the total number of protons in the nucleus of an atom. Each element has a unique atomic number which defines its chemical properties. For example, the sulfur atom in the exercise has an atomic number of 16, meaning it contains 16 protons.

Having a fixed atomic number, elements can be systematically organized in the periodic table, which is a handy tool showing elements in order of increasing atomic numbers. This atomic number is essential in determining the type of ion that forms when atoms gain or lose electrons during chemical reactions.

The mass number, denoted as 'A', plays a crucial part when discussing isotopes and determining the mass of an atom. Mass number is the sum of the protons and neutrons in an atom's nucleus. Unlike the atomic number, the mass number is not fixed for a given element, as elements can have different numbers of neutrons.

In our exercise, two sulfur ions are presented - one with a mass number of 34 and the other with 32. This variance arises due to the different number of neutrons present (18 and 16 respectively) added to the constant number of protons for sulfur (16). By indicating the mass number in the ion notation, as shown in the provided solutions (\(S^{34}_{16} {2-}\) and \(S^{32}_{16} {2-}\)), we clarify which isotope of sulfur we are referring to.

An atom becomes an ion when it gains or loses electrons, resulting in a net charge – known as the ion charge. This charge is often indicated as a superscript next to the element's symbol in ion notation. If an ion has more electrons than protons, it gets a negative charge (an anion), and if it has fewer electrons, the charge is positive (a cation).

The sulfur ions in our exercise have 18 electrons compared to 16 protons, thus carrying a charge of -2, indicating an excess of two electrons. This extra negative charge is represented as '2-' in the ion notation, \(S^{34}_{16} {}^2-\) and \(S^{32}_{16} {}^2-\), signifying that the sulfur ion is an anion.

Isotopes are variants of a particular chemical element that have the same number of protons (and hence the same atomic number) but a different number of neutrons, resulting in different mass numbers. All isotopes of an element share similar chemical properties because they have the same number of electrons in a neutral state.

The exercise presented two different isotopes of sulfur, both with 16 protons but varying neutron counts. This highlights the concept that while isotopes have different physical properties (e.g., mass), they are chemically indistinguishable. Isotopes are essential for various applications in medicine, such as radioactive tracing, and in research, such as dating of archaeological samples.