Problem 61 - Chemistry The Molecular Science

Question

Write the correct formula for each compound. (a) Bromine trichloride (b) Xenon trioxide (c) Diphosphorus tetrafluoride (d) Oxygen difluoride

Step-by-Step Solution

Answer

(a) BrCl₃, (b) XeO₃, (c) P₂F₄, (d) OF₂.

Step 1: Understanding nomenclature rules

Before we start, it's crucial to understand the systematic nomenclature and the prefixes used for naming compounds. The elements involved often use Greek prefixes like mono-, di-, tri-, tetra-, etc., indicating the number of atoms present. For binary compounds, the element with the more positive character is named first, followed by the second element with an -ide suffix.

Step 2: Analyzing Bromine trichloride

In bromine trichloride, the prefix 'tri-' signifies three atoms of chlorine ( Cl ) bonded with one atom of bromine ( Br ). The formula will be BrCl 3 .

Step 3: Analyzing Xenon trioxide

For xenon trioxide, the term 'tri-' indicates three oxygen ( O ) atoms combined with one xenon ( Xe ) atom. The formula is represented as XeO 3 .

Step 4: Analyzing Diphosphorus tetrafluoride

For diphosphorus tetrafluoride, 'di-' means two phosphorus ( P ) atoms and 'tetra-' indicates four fluorine ( F ) atoms. Therefore, the formula is P 2 F 4 .

Step 5: Analyzing Oxygen difluoride

Oxygen difluoride contains one oxygen ( O ) atom paired with two fluorine ( F ) atoms. The prefix 'di-' indicates the presence of two fluorine atoms. Thus, the molecular formula is OF 2 .

Key Concepts

Binary Compounds

Binary compounds are one of the simplest forms of chemical compounds. They consist of two different elements. These elements can be metals, non-metals, or metalloids. Each compound has its own unique properties and characteristics based on the elements involved.
Understanding binary compounds is essential in chemistry, as they form the basis for more complex molecules. Generally, when writing the formula for a binary compound:

• The element with a more positive character is named first. This is often a metal or the least electronegative element.
• The second element is named with an 'ide' suffix, such as chloride for chlorine or fluoride for fluorine.

Take, for example, Bromine trichloride (BrCl₃). Bromine, being less electronegative than chlorine, comes first, followed by chlorine with a tri- prefix because three chlorine atoms are present. Mastering binary compounds is a stepping stone to understanding more complex chemical nomenclature.

Greek Prefixes

In chemical nomenclature, Greek prefixes are a critical component used to indicate the number of atoms of each element in a compound. This becomes incredibly useful when dealing with compounds that are not ionic.
Here are some common Greek prefixes:

• Mono- for one atom
• Di- for two atoms
• Tri- for three atoms
• Tetra- for four atoms
• Penta- for five atoms
• Hexa- for six atoms

These prefixes help provide clarity, especially when a particular element can form more than one compound with another element. For example, in Diphosphorus tetrafluoride (P₂F₄), 'di-' indicates two phosphorus atoms and 'tetra-' indicates four fluorine atoms. This systematic method of naming ensures there is no confusion about the number of each type of atom present in a molecule.

Molecular Formulas

A molecular formula conveys crucial information about the atoms in a molecule. It represents the actual number and type of atoms in a compound, providing insight into its composition.
For example:

• The formula for Bromine trichloride is BrCl₃. This indicates one bromine atom attached to three chlorine atoms.
• The formula XeO₃ represents one xenon atom bonded to three oxygen atoms in Xenon trioxide.
• OF₂ indicates a molecule of Oxygen difluoride with one oxygen atom and two fluorine atoms.

The molecular formula is an integral part of chemical communication as it reveals not only the types of elements involved but also their proportion in the compound. Understanding molecular formulas is foundational in predicting the behavior and interaction of compounds.

Systematic Naming Rules

Chemical nomenclature follows a specific set of rules that enable chemists to name compounds systematically. This precision helps prevent ambiguity and ensures consistency in how compounds are referred to globally.

• For binary compounds, start with the element with a more "positive" character or lower electronegativity.
• Use Greek prefixes to denote the number of atoms, but do not use 'mono-' for the first element.
• The second element gets the 'ide' suffix, indicating it's a compound. Examples include chloride, oxide, and fluoride.

Systematic naming aims to eliminate confusion by standardizing how compounds are named across the globe. For instance, taking Diphosphorus tetrafluoride, we see 'di-' denotes two phosphorus atoms and 'tetra-' shows four fluorine atoms. Being consistent with these rules ensures that chemical names are unambiguous and readily understood by anyone familiar with the nomenclature system.