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Before there were chemists, there were alchemists, who sought to make a living off turning cheaper metals into gold. While alchemy formed the foundations of modern chemistry and its various branches, it was always a doomed subject. As we know now, gold is an element, or specific type of atom, defined by proton count. Elements are the fundamental substances that make up matter. One type cannot become another through chemical changes.

Each element is defined by the number of protons it has. The periodic table starts with hydrogen, which has one proton, and continues. The atomic number, or number of protons, is written above the abbreviation of the name.

Protons are located in the nucleus of the atom, which is not altered during chemical reactions. Because of this, one type of element cannot chemically become another type.

Instead, multiple atoms can form chemical bonds by sharing or giving away their electrons, creating compounds, or chemicals made of multiple elements. These have different properties than the single atoms do.

An element is the simplest form of matter that consists of atoms of the same type and cannot be broken down chemically. There are over 90 different types that occur in nature, and more that have been synthesized in a lab.

The type of element is determined by the number of protons it has, but the number of electrons or neutrons can vary. When an atom of the element has a different number of neutrons, it is called an isotope. When the atom has a different number of electrons, it is called an ion. If there are more electrons than protons, it is a negative ion, and if there are more protons than electrons, it's a positive ion. If the number of protons and electrons are equal, there is no charge!

Elements can come in different phases or states, such as solid, liquid, or gas depending on the temperature. They can also vary depending on how tightly packed they are. For example, carbon can make coal, graphite, or even diamond depending on how tightly they are packed!

When two or more elements combine, they make a chemical compound. An example is water, with the molecular formula ${H_2O}$, which is made of hydrogen and oxygen. When two or more substances mix together but are not chemically combined, they make a mixture. An example is when you put cream or sugar in your coffee. The substances are mixed together to make a solution, but they don't merge together chemically. Plus, with mixtures, you can separate the individual substances.

Elements cannot be broken down into simpler substances. Atoms that have the same number of protons are said to be the same type of element. They can vary in number of neutrons and electrons, but in order to be the same type they must have the same number of protons. There are currently 118 known types, and they are organized into the periodic table.

Since elements are defined by protons, every atom that has 20 protons is calcium, and every atom of calcium has 20 protons. The number of protons is also indicated by the atomic number.

Differences in the number of neutrons are called isotopes. That is to say, if an atom with 1 proton and 1 neutron is hydrogen, and so is an atom with 1 proton and 2 neutrons. These two atoms are isotopes of each other since they are both hydrogen, but have a different number of neutrons.

Differences in the number of electrons electrons are called ions. For example, a sulfur atom should have 16 electrons, but if it has 17 electrons, it is called a sulfur ion.

(Video) Difference Between Atoms and Elements

by Wayne Breslyn

In this video, Dr. B describes the difference between elements and atoms. He also talks about protons, neutrons, and electrons in an atom and how they make isotopes.

The interactive application he uses can be found on the PhET website.