Using the periodic table to guide you, predict the chemical formula and name of the compound formed by the following elements: \((\mathbf{a})\) Ga and \(\mathrm{F},(\mathbf{b})\) Li and \(\mathrm{H},(\mathbf{c})\) Al and \(\mathrm{I},(\mathbf{d}) \mathrm{K}\) and \(\mathrm{S}\)

Understanding valency is essential for predicting how elements will bond together. Valency refers to the combining capacity of an element, indicating the number of electrons an atom is willing to gain, lose, or share to achieve a full outer shell, resembling that of the noble gases. In chemical bonding, elements tend to achieve stability by acquiring the electronic configuration of the nearest noble gas, leading to the formation of ionic or covalent bonds.

For example, in the pairing of Gallium (Ga) and Fluorine (F), Gallium with a valency of +3 will 'seek' three Fluorine atoms each with a valency of -1 to balance its charge and achieve chemical stability. This creates ionic bonds and results in the formation of Gallium Fluoride (GaF₃). Valency dictates the ratio in which different atoms combine, hence plays a pivotal role in predicting the formula of compounds formed through chemical bonding.

The periodic table groups are like neighborhoods that categorize elements based on their chemical properties, which are determined by the element's electron configuration. Groups, also known as families, run vertically down the periodic table and are numbered from 1 to 18. Elements within the same group typically have the same valency.

For example, Lithium (Li) belongs to Group 1, which contains alkali metals known for having a valency of +1. This characteristic is crucial when predicting the formation of ionic compounds. Knowing that Hydrogen (when it acts like a halogen with alkali metals) has a valency of -1, it's clear that Lithium and Hydrogen will combine in a 1:1 ratio, leading to the formation of Lithium Hydride (LiH). Familiarity with periodic table groups aids immensely in understanding how elements will behave during compound formation.

The naming of chemical compounds, also known as nomenclature, follows specific rules that allow scientists to communicate formulae in a standardized way. For ionic compounds, the cation (positive ion) is named first, followed by the anion (negative ion), with the latter often ending in '-ide.'

Thus, the compound with the formula AlI₃ is named Aluminum Iodide; 'Aluminum' reflects the cation Al³⁺ and 'Iodide' is derived from the anion I^-. In more complex scenarios involving polyatomic ions, other suffixes like '-ate' or '-ite' may be used. Learning these rules simplifies the process of converting chemical formulas into their corresponding names, a critical skill in the study of chemistry.

Ionic compounds are formed when metals transfer electrons to non-metals, creating ions that attract each other due to their opposite charges. This process often occurs between metals from the left side of the periodic table and non-metals from the right side, excluding noble gases.

Looking at Potassium (K) and Sulfur (S), Potassium, an alkali metal, loses one electron to form K⁺, while Sulfur, a non-metal, gains two electrons to form S^2-. To neutralize these charges, two Potassium ions will bond with one Sulfur ion, resulting in the ionic compound K₂S, known as Potassium Sulfide. Recognizing the propensity for certain groups to lose or gain electrons can greatly assist in the prediction of ionic compounds and their ratios.