Chemical Names & Formulas: Which Pair Is Correct?

Hey there, chemistry enthusiasts! Today, we're diving into the fascinating world of chemical nomenclature and formulas. It's like learning a new language, but instead of words, we're dealing with elements and compounds. The big question we're tackling is: Which chemical name is correctly paired with its chemical formula? Let's break down the options and figure it out together.

Decoding Chemical Names and Formulas

Before we jump into the specific choices, let's brush up on some key concepts. Understanding these fundamentals will make identifying the correct pair a breeze. So, let’s start with chemical nomenclature. Chemical nomenclature is essentially the system we use to name chemical compounds. It's super important because it allows chemists worldwide to communicate clearly and avoid confusion. Think of it as the universal language of chemistry. Just imagine the chaos if everyone used different names for the same substance!

Now, let’s talk about chemical formulas. A chemical formula is a shorthand way of representing a molecule or compound. It tells us which elements are present and in what proportions. For example, the familiar water molecule is written as $H _2 O$, indicating two hydrogen atoms and one oxygen atom. Chemical formulas can be simple, like $NaCl$ (sodium chloride, or table salt), or more complex, like $C _6 H _{12} O _6$ (glucose, a type of sugar). Mastering the art of reading and interpreting chemical formulas is a cornerstone of chemistry. You’ll see them everywhere, from textbooks to lab experiments to everyday product labels. Being able to quickly decipher a formula gives you a peek into the compound's composition and behavior.

Understanding Oxidation States and Roman Numerals

One crucial aspect of chemical nomenclature involves oxidation states. An oxidation state, also known as an oxidation number, is a measure of the degree of oxidation of an atom in a chemical compound. It's basically a way of keeping track of how many electrons an atom has gained or lost compared to its neutral state. Oxidation states are often indicated using Roman numerals in the names of ionic compounds, especially those involving transition metals. Transition metals are elements that can exhibit multiple oxidation states, which means they can form different ions with varying charges. Iron, for example, can exist as $Fe ^{2+}$ (iron(II)) or $Fe ^{3+}$ (iron(III)).

The Roman numeral tells us the charge on the metal cation. So, iron(II) indicates an iron ion with a +2 charge, while iron(III) signifies a +3 charge. Why is this important? Because the charge of the metal ion directly affects the chemical formula of the compound it forms. The overall compound must be electrically neutral, meaning the positive and negative charges must balance out. For example, iron(II) oxide has the formula $FeO$ because the +2 charge of the $Fe ^{2+}$ ion is balanced by the -2 charge of the $O ^{2-}$ ion. On the other hand, iron(III) oxide has the formula $Fe _2 O _3$ because two $Fe ^{3+}$ ions (total charge +6) are needed to balance the charge of three $O ^{2-}$ ions (total charge -6). Without Roman numerals, we wouldn't be able to distinguish between these two different iron oxides, which have different properties and applications.

Ionic Compounds and Balancing Charges

Ionic compounds are formed through the electrostatic attraction between positively charged ions (cations) and negatively charged ions (anions). These ions are created when atoms gain or lose electrons to achieve a stable electron configuration, typically resembling that of a noble gas. When naming ionic compounds, we generally follow a simple set of rules. The cation (metal) is named first, followed by the anion (nonmetal). For monatomic anions (ions formed from a single atom), we change the ending of the element name to "-ide." For example, chlorine becomes chloride ($Cl ^-$), oxygen becomes oxide ($O ^{2-}$), and nitrogen becomes nitride ($N ^{3-}$).

One of the most critical steps in writing the formula of an ionic compound is balancing the charges. As we mentioned earlier, the overall compound must be electrically neutral. This means the total positive charge from the cations must equal the total negative charge from the anions. To achieve this balance, we often need to use subscripts in the chemical formula. Subscripts indicate the number of each type of ion present in the compound. Let's illustrate this with an example. Suppose we want to write the formula for aluminum oxide. Aluminum (Al) typically forms a +3 ion ($Al ^{3+}$), while oxygen (O) forms a -2 ion ($O ^{2-}$). To balance the charges, we need two aluminum ions (+3 each, total +6) and three oxide ions (-2 each, total -6). Therefore, the correct formula for aluminum oxide is $Al _2 O _3$. Mastering the art of balancing charges is essential for accurately representing ionic compounds.

Analyzing the Options

Now that we've reviewed the basics, let's tackle the multiple-choice options. We'll carefully examine each pair to determine if the chemical name and formula match up correctly.

A. tin(IV) bromide, $SnBr _4$

• Tin (Sn) is a metal that can exhibit multiple oxidation states. The (IV) indicates that tin has a +4 charge in this compound ($Sn ^{4+}$).
• Bromide (Br) is a halogen that typically forms a -1 ion ($Br ^-$).
• To balance the +4 charge of tin, we need four bromide ions (4 x -1 = -4). Therefore, the formula $SnBr _4$ correctly represents tin(IV) bromide.

This option looks promising! Let's keep it in mind as we evaluate the others.

B. iron(II) oxide, $Fe _2 O _3$

• Iron (Fe), as we discussed earlier, is a transition metal that can form both +2 and +3 ions. The (II) indicates a +2 charge ($Fe ^{2+}$).
• Oxide (O) is oxygen, which typically forms a -2 ion ($O ^{2-}$).
• To balance the charges, we would need one $Fe ^{2+}$ and one $O ^{2-}$, resulting in the formula $FeO$. The given formula, $Fe _2 O _3$, actually represents iron(III) oxide.

This option is incorrect. The formula doesn't match the name.

C. potassium chloride, $K _2 Cl _2$

• Potassium (K) is an alkali metal that always forms a +1 ion ($K ^+$).
• Chloride (Cl) is chlorine, which forms a -1 ion ($Cl ^-$).
• To balance the charges, we need one potassium ion and one chloride ion, resulting in the formula $KCl$. The given formula, $K _2 Cl _2$, is incorrect.

This option is also incorrect.

D. aluminum fluorate, $AlF _3$

• Aluminum (Al) typically forms a +3 ion ($Al ^{3+}$).
• Fluoride (F) is fluorine, which forms a -1 ion ($F ^-$).
• To balance the +3 charge of aluminum, we need three fluoride ions (3 x -1 = -3). The formula $AlF _3$ correctly represents aluminum fluoride.

However, the name is slightly off. The correct name should be aluminum fluoride, not aluminum fluorate. The "-ate" suffix usually indicates the presence of oxygen in a polyatomic anion (like sulfate, $SO _4 ^{2-}$). Fluoride is a simple monatomic anion.

While the formula is correct, the name makes this option incorrect.

The Verdict

After carefully analyzing each option, it's clear that the correct answer is:

A. tin(IV) bromide, $SnBr _4$

Both the name and the formula accurately represent the compound. The other options either had mismatched names and formulas or a slight error in the name itself.

Key Takeaways

This exercise highlights the importance of understanding chemical nomenclature, oxidation states, and balancing charges. By mastering these concepts, you'll be well-equipped to tackle a wide range of chemistry problems. Remember, chemistry is like a puzzle, and each piece (element, ion, formula) needs to fit together correctly. Keep practicing, and you'll become a chemical equation-solving pro in no time!

To deepen your understanding of chemical nomenclature and practice naming compounds, explore resources like the International Union of Pure and Applied Chemistry (IUPAC) website. IUPAC is the authority on chemical nomenclature, and their website provides comprehensive guidelines and information.