Understanding Fundamental Chemistry Terms

Fundamental Chemistry Concepts

Mixtures: Homogeneous vs. Heterogeneous

Homogeneous means it has a uniform appearance; at first glance, there are no distinct components. A heterogeneous mixture consists of several substances that are visibly separate.

Understanding Solutions

A solution is a homogeneous mixture, consisting of two or more pure substances present in varying amounts. These components can be separated by physical processes.

Solution Components: Solvent and Solute

Normally, the substance found in the largest quantity is called the solvent. The other substances are called solutes.

Solution Concentration: Concentrated/Diluted

A solution is concentrated when it contains a large amount of solute. A solution is dilute when it contains a small amount of solute.

Pure Substances Defined

A pure substance is one that cannot be decomposed into other substances by any physical process of separation.

Elements

An element is a pure substance that cannot be broken down into simpler substances.

Metals and Nonmetals

Metals tend to be solid due to their high melting and boiling points. They can often be formed into wire and sheet metal, and they are good conductors. Nonmetals are usually gases or liquids due to their relatively low melting and boiling points. They do not conduct heat or electricity well.

Atomic Structure

The Atom

The atom consists of a central region called the nucleus, which contains protons and neutrons. Around the nucleus is a cloud of electrons. In a neutral atom, the number of protons equals the number of electrons; thus, atoms are electrically neutral.

Ions Explained

Concept of an Ion

An atom is neutral when it has an equal number of positive (protons) and negative (electrons) charges. If an atom loses some electrons, it develops a net positive charge. If it gains electrons, the net charge becomes negative. In both cases, it becomes an ion. An ion is an atom or group of atoms that is electrically charged.

Cations and Anions

There are two types of ions: A cation (or positive ion) is formed when an atom or group of atoms loses one or more electrons. An anion (or negative ion) is formed when an atom or group of atoms gains one or more electrons.

Isotopes Explained

Concept of an Isotope

Isotopes are atoms of the same element that have the same atomic number (Z, the number of protons in the nucleus) but different mass numbers (A, the sum of the number of neutrons and protons in the nucleus). Therefore, isotopes of an element differ in the number of neutrons.

Element Mass

Calculating Element Mass

The mass of most elements is not an integer because it is calculated as a weighted average of the masses of its naturally occurring isotopes. This average takes into account the relative abundance (percent) of each isotope.