Write Lewis dot symbols for the following ions: (a) \(\mathrm{Li}^{+},(\mathrm{b}) \mathrm{Cl}^{-},(\mathrm{c}) \mathrm{S}^{2-},(\mathrm{d}) \mathrm{Sr}^{2+}\) (e) \(\mathrm{N}^{3+}\).

Valence electrons play a pivotal role in chemical bonding and reactions. They are the outermost electrons of an atom and are vital in determining how an element will react with others. For instance, lithium (Li) has one valence electron, which makes it highly reactive as it tends to lose that one electron to achieve a stable electronic configuration similar to the noble gases.

In the case of our exercise, understanding valence electrons is the first step in drawing Lewis dot symbols for ions. The Lewis dot symbols represent an atom’s valence electrons as dots around the element’s symbol. By referring to the periodic table, we can quickly identify that chlorine (Cl) has seven valence electrons, sulphur (S) six, strontium (Sr) two, and nitrogen (N) five. These electrons play a crucial role in the formation of ions. When these atoms gain or lose electrons, it is the valence electrons that are exchanged.

The concept of ionic charge is essential when dealing with ions, which are atoms or molecules that have gained or lost electrons and thus have a net electrical charge. Cations are positively charged ions, which occur when an atom loses electrons; anions are negatively charged ions, which form when an atom gains electrons.

Using lithium as an example from our exercise, when it loses one valence electron, it becomes \(\mathrm{Li}^+\), a cation with a single positive charge. Conversely, chlorine gains an electron to become \(\mathrm{Cl}^-\), an anion with a single negative charge. The ionic charge affects how these atoms interact with each other and dictates the way we represent them with Lewis dot symbols. It’s fundamental to understand that the aim of an ion is often to reach a stable electronic configuration, which is typically achieved by having eight valence electrons - reflecting the noble gas structure, an occurrence known as the octet rule.

The periodic table is not merely a display of chemical elements, but it’s a comprehensive tool that reveals a wealth of information about the properties of these elements, including their valence electrons and tendencies to form certain ionic charges. It's organized in such a way that elements with similar properties are in the same columns, also known as groups.

The number of valence electrons for an element can usually be deduced from its group number in the periodic table. For example, lithium is in the first group, hence it has one valence electron, while chlorine is in the seventh group, hinting towards its seven valence electrons. Learning to navigate the periodic table allows for predictions about how atoms will interact and the types of ions they will form, making it an indispensable tool for understanding exercises like the Lewis dot symbols for ions.