Learning Outcomes
By the end of this lesson, students will be able to:
i. Define and explain ions, molecular ions, formula units, and free radicals.
ii. Identify each of these chemical species.
iii. Develop a basic understanding of the properties and behavior of ions, molecular ions, formula units, and free radicals.
Introduction
The world around us is made up of matter, which is anything that has mass and occupies space. Matter can exist in three states: solid, liquid, and gas. All matter is composed of tiny particles called atoms. Atoms are the smallest units of matter that can participate in chemical reactions.
Atoms can combine with each other to form molecules. A molecule is a group of two or more atoms that are held together by chemical bonds. Molecules can be either neutral or charged. Neutral molecules have the same number of protons and electrons, so they have no net charge. Charged molecules, called ions, have a different number of protons and electrons, so they have a net positive or negative charge.
There are two types of ions: cations and anions. Cations are positively charged ions, and anions are negatively charged ions. Cations are formed when an atom loses one or more electrons, while anions are formed when an atom gains one or more electrons.
Atoms can also combine with each other to form molecular ions. A molecular ion is a group of atoms that is held together by chemical bonds and has a net charge. Molecular ions can be either cations or anions.
In addition to ions and molecular ions, there are two other important chemical species: formula units and free radicals. A formula unit is a group of atoms that are written together in a way that shows their relative numbers and charges. Formula units are not always molecules, and they can be either neutral or charged.
Free radicals are highly reactive atoms or molecules that have unpaired electrons. Unpaired electrons are electrons that are not shared with any other atom. Free radicals are often unstable and can react with other molecules to form new compounds.
i. Ions: Ions are atoms or groups of atoms that have lost or gained electrons, resulting in a net positive or negative charge. Cations are positively charged ions, while anions are negatively charged ions.
ii. Molecular Ions: Molecular ions are polyatomic ions that have a net charge. They are formed when a group of atoms loses or gains electrons.
iii. Formula Units: Formula units are the simplest representation of a compound, showing the relative numbers and charges of the atoms present. They may not represent actual molecules and can be neutral or charged.
iv. Free Radicals: Free radicals are atoms or molecules with unpaired electrons, making them highly reactive. They are often intermediates in chemical reactions.
Examples
Ions: Sodium ion (Na+), chloride ion (Cl-), magnesium ion (Mg2+), sulfate ion (SO42-)
Molecular Ions: Ammonium ion (NH4+), hydroxide ion (OH-), cyanide ion (CN-)
Formula Units: NaCl (sodium chloride), CaCO3 (calcium carbonate), H2O (water)
Free Radicals: Hydrogen radical (H•), oxygen radical (O•), hydroxyl radical (OH•)
Chemical species, including ions, molecular ions, formula units, and free radicals, are essential components of matter and play a crucial role in various chemical processes. Understanding their properties and behavior is fundamental to comprehending the intricate world of chemistry.
