Write formulas for ionic compounds formed between (a) \(\mathrm{Al}\) and \(\mathrm{Br},\) (b) \(\mathrm{Rb}\) and \(\mathrm{I},\) (c) \(\mathrm{Sr}\) and \(\mathrm{S}\), (d) \(\mathrm{Mg}\) and \(\mathrm{N}\), (e) Ga and \(\mathrm{O},\) and \((\mathbf{f}) \mathrm{Sr}\) and \(\mathrm{F}\)

When it comes to writing formulas for ionic compounds, the foundation lies in understanding ionic charges. Atoms can gain or lose electrons to form ions, which are charged particles. Metals often lose electrons, forming positively charged ions, while non-metals tend to gain electrons, becoming negatively charged ions.

Each type of atom has a characteristic ion charge that can be predicted based on its position on the periodic table. For example, group 1 elements like Rubidium (Rb) lose one electron to form a +1 charge, whereas group 17 elements like Bromine (Br) and Iodine (I) gain one electron and thus, have a -1 charge. Recognizing these patterns is key to writing chemical formulas for ionic compounds effectively.

Chemical formulas are like recipes that specify which ions and how many of each type are needed to form a compound. The formula is a shorthand representation using the elements' symbols from the periodic table and numerical subscripts to indicate the quantity of atoms.

For instance, in the formation of a compound between Magnesium (Mg) and Nitrogen (N), the formula Mg₃N₂ reflects the need for three Mg ions each with a +2 charge to balance out the -3 charge of two N ions. This ensures the overall neutrality of the compound. Understanding how to interpret and write these formulas is crucial for grasping the composition of different ionic compounds.

Ions combine based on one simple rule: the compound must be electrically neutral. In other words, the positive and negative charges must balance out. To achieve this, ions come together in ratios that offset their charges.

For example, Aluminum (Al) has a +3 charge, while Bromine (Br) has a -1 charge. Three Bromide ions, each with a -1 charge, are needed to balance out the single Aluminum ion's +3 charge. This combining of ions, known as ion pairing, is the second step in creating ionic compounds. The end goal is to reach a state where the total positive charge equals the total negative charge, resulting in a stable, neutral compound.

The art of crafting the correct formula for an ionic compound relies on balancing ionic charges. The principle is to multiply the ions' charges to determine the lowest ratio of atoms that balances the overall charge to zero.

For instance, Strontium (Sr) has a +2 ion, while Sulfur (S) has a -2 ion. The charges are equal and opposite, so they balance each other with a one-to-one ratio, forming SrS. However, when Strontium (Sr) pairs with Fluorine (F), which has a -1 charge, two Fluorine ions are required to counterbalance the +2 charge from one Strontium ion, resulting in SrF₂. Mastering this process of balancing charges is essential to write the formula for any ionic compound correctly.