a. Determine whether each of the following compounds is likely to exist as a molecule, or as an ionic compound: i. Hydrogen fluoride; HF ii. Silicon tetrachloride; \(\mathrm{SiCl}_{4}\) iii. Elemental sulfur as \(\mathrm{S} 8\) iv. Disodium dioxide; \(\mathrm{Na}_{2} \mathrm{O}\) v. \(\mathrm{PF}_{3}\) vi. \(\mathrm{Be}_{3} \mathrm{~N}_{2}\) vii. AlP viii. CBr4

In chemistry, understanding the nature of a compound starts with understanding its chemical bonding, the strong attractive force that holds atoms together within a molecule or crystal structure. Two primary types of bonding are ionic and covalent.

Ionic bonding occurs when there is a complete transfer of electrons from one atom to another, typically between a metal and a nonmetal. This transfer creates ions, with the metal becoming positively charged (cation) and the nonmetal becoming negatively charged (anion). The opposite charges attract, resulting in an ionic bond and forming an ionic compound.

In contrast, covalent bonding happens when two nonmetals share electrons. There's usually a balance in electronegativity or a moderate difference between the atoms allowing them to share electrons rather than transferring them, thus binding the atoms together to form a molecule or a covalent compound. Some compounds, like water, have small differences in electronegativity between the atoms, which leads to a polar covalent bond.

The periodic table of elements is a systematic arrangement of the chemical elements, ordered by their atomic numbers, electron configurations, and recurring chemical properties. Elements are generally categorized as metals, nonmetals, and metalloids (also known as semimetals).

• Metals are typically found on the left side and in the center of the periodic table. They are generally shiny, conductive, and capable of forming cations by losing electrons.
• Nonmetals are found on the right side (excluding the noble gases) and are varied in appearance. They tend to gain electrons to form anions and are not as conductive as metals.
• Metalloids are found along the zigzag line that divides metals and nonmetals. They exhibit properties intermediate between those of metals and nonmetals and can behave as either under different conditions.

By knowing the location and properties of these elements, you can predict the type of bonding they will likely engage in when they form compounds.

Electronegativity is the measure of an atom's ability to attract and hold onto electrons when it forms a chemical bond. This concept is crucial for determining the type of bond two atoms will form. An electronegativity difference often dictates whether a bond will be ionic, polar covalent, or nonpolar covalent.

In general, the greater the difference in electronegativity between two atoms, the more ionic the bond is. For example, metals having lower electronegativities than nonmetals, often leading to the formation of ionic compounds. Small differences result in polar covalent bonds, while atoms with similar electronegativities (typically nonmetals) result in nonpolar covalent bonds.

With the Step by Step Solution explaining molecular and ionic compounds using electronegativity differences, students can better predict and understand compound formation. The examples from the original exercise illustrate how to apply electronegativity to decide whether a compound is ionic or molecular.