What Are the First 20 Elements?

Hydrogen is the first element on the periodic table. It's also the most abundant element in the universe. Science Picture Co / Getty Images

One common chemistry assignment is to name or even memorize the first 20 elements and their symbols. The elements are ordered in the periodic table according to increasing atomic number. This is also the number of protons in each atom.

These are the first 20 elements, listed in order:

1 - H - Hydrogen
2 - He - Helium
3 - Li - Lithium
4 - Be - Beryllium
5 - B - Boron
6 - C - Carbon
7 - N - Nitrogen
8 - O - Oxygen
9 - F - Fluorine
10 - Ne - Neon
11 - Na - Sodium
12 - Mg - Magnesium
13 - Al - Aluminum
14 - Si - Silicon
15 - P - Phosphorus
16 - S - Sulfur
17 - Cl - Chlorine
18 - Ar - Argon
19 - K - Potassium
20 - Ca - Calcium

Using Element Symbols and Numbers

The number of the element is its atomic number, which is the number of protons in each atom of that element. The element symbol is a one- or two-letter abbreviation of the element's name (although sometimes it refers to an old name, like K is for kalium). The element name can tell you something about its properties. Elements with names ending with -gen are nonmetals that are gases in pure form at room temperature. Elements that have names ending with -ine belong to a group of elements called halogens. Halogens are extremely reactive and readily form compounds. Element names ending with -on are noble gases, which are inert or nonreactive gases at room temperature. Most element names end with -ium. These elements are metals, which are usually hard, shiny, and conductive.

What you cannot tell from an element name or symbol is how many neutrons or electrons an atom possesses.

To know the number of neutrons, you need to know the isotope of the element. This is indicated using numbers (superscripts, subscripts, or following the symbol) to give the total number of protons and neutrons. For example, carbon-14 has 14 protons and neutrons. Since you know all atoms of carbon have 6 protons, the number of neutrons is 14 - 6 = 8.

Ions are atoms that have different numbers of protons and electrons. Ions are indicated using a superscript after the element symbol that states whether the charge on the atom is positive (more protons) or negative (more electrons) and the quantity of the charge. For example, Ca2+ is the symbol for a calcium ion that has a positive 2 charge. Since the atomic number of calcium is 20 and the charge is positive, this means the ion has 20 - 2 or 18 electrons.

What Is a Chemical Element?

In order to be an element, a substance has to at least have protons, since these particles define the type of element. Most elements consist of atoms, which contain a nucleus of protons and neutrons surrounded by a cloud or shell of electrons. Elements are considered the basic building blocks of matter because they are the simplest form of matter that cannot be divided using any chemical means.

Learn More

Knowing the first 20 elements is a good way  to start learning about elements and the periodic table. From here, suggestions for the next step are to review the full element list and learn how to memorize the first 20 elements. Once you feel comfortable with the elements, test yourself by taking the 20 element symbol quiz.

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Helmenstine, Anne Marie, Ph.D. "What Are the First 20 Elements?" ThoughtCo, Aug. 3, 2017, thoughtco.com/what-are-the-first-20-elements-608820. Helmenstine, Anne Marie, Ph.D. (2017, August 3). What Are the First 20 Elements? Retrieved from https://www.thoughtco.com/what-are-the-first-20-elements-608820 Helmenstine, Anne Marie, Ph.D. "What Are the First 20 Elements?" ThoughtCo. https://www.thoughtco.com/what-are-the-first-20-elements-608820 (accessed March 21, 2018).