Question

Write chemical formulas for compounds containing: (a) three iron atoms for every four oxygen atoms (b) one phosphorus atom for every three chlorine atoms (c) one phosphorus atom for every five chlorine atoms (d) two silver atoms for every oxygen atom

Short answer

The chemical formulas are (a) Fe3O4, (b) PCl3, (c) PCl5, (d) Ag2O.

Step-by-step solution

Determine the Chemical Symbols

Identify the chemical symbols for the elements involved. For part (a), iron is Fe and oxygen is O. For parts (b) and (c), phosphorus is P and chlorine is Cl. For part (d), silver is Ag and oxygen is O.

Create the Chemical Formula for (a)

Since there are three iron atoms for every four oxygen atoms, we represent this ratio with the subscripts in the chemical formula. The formula becomes Fe3O4.

Create the Chemical Formula for (b)

As there is one phosphorus atom for every three chlorine atoms, the chemical formula is PCl3.

Create the Chemical Formula for (c)

Given there is one phosphorus atom for every five chlorine atoms, the chemical formula is PCl5.

Create the Chemical Formula for (d)

With two silver atoms for every oxygen atom, the chemical formula is Ag2O.

Key concepts

Chemical Symbols

The language of chemistry is rich with symbols, each denoting a specific element from the periodic table. Chemical symbols are shorthand representations of chemical elements. For example, the symbol 'H' stands for hydrogen and 'O' represents oxygen. These symbols are universally recognized and allow chemists to communicate formulas and reactions without ambiguity.

Understanding chemical symbols is the first step toward writing chemical formulas. They are comprised of one or two letters, with the first letter always capitalized and the second letter, if present, in lowercase. For instance, 'Fe' represents iron, 'Cl' for chlorine, and 'Ag' denotes silver. These elemental abbreviations are derived from either their English names or their Latin names—such as 'Fe' for ferrum (iron) and 'Ag' for argentum (silver).

Subscripts in Chemistry

Subscripts play a crucial role in chemical formulas, indicating the number of atoms of a given element within a compound. These numbers are written as small figures below the line of text. For example, in the chemical formula for water, H2O, the '2' is a subscript that tells us there are two hydrogen atoms for every one oxygen atom.

When writing chemical formulas, if more than one atom of a particular element is present, a subscript is used to convey this quantity. If only one atom is present, the subscript one is typically omitted for simplicity. It's vital to treat subscripts with precision, as changing the subscript would alter the compound’s composition and potentially its properties. In our exercise example, for the compound containing three iron atoms for every four oxygen atoms, the chemical formula is represented as Fe3O4—thus illustrating the specific ratio of atoms.

Compound Composition

Compound composition refers to the specific elements and the number of each atom that make up a chemical compound. This information is encapsulated in the chemical formula of the compound. The formula not only indicates the kinds of atoms present but also the precise ratio in which the atoms combine to form the compound.

For instance, in PCl5, the composition is one phosphorus atom to five chlorine atoms. Similarly, Ag2O denotes a compound with two silver atoms for every oxygen atom. Compound composition is foundational for understanding the properties of the substance, predicting the outcomes of chemical reactions, and creating new compounds through synthesis. Properly interpreting and writing these formulas allow chemists and students alike to grasp the intricate balance of elements that constitute the diverse array of chemical compounds found in nature and used in various applications.