The Periodic Table

The periodic table was created by Dmitri Mendeleev in 1869. Find out about this classification system and its history on this expedition.

This story was created for the Google Expeditions project by Vida Systems, now available on Google Arts & Culture

The Modern Periodic TableOriginal Source: Royal Society for Chemistry (UK)

It was created to help categorize the known elements, ordering them by their atomic weight. The table also suggested that there were elements yet to be discovered by science. To date, scientists have discovered or created 118 different elements. 

The Periodic Table

The periodic table was created by Dmitri Mendeleev in 1869. It was created to help categorize the known elements, ordering them by their atomic weight. The table also suggested that there were elements yet to be discovered by science.

To date, scientists have discovered or created 118 different elements. 


An element is a substance made up of only one type of atom. Many elements mix together to form other substances. For example, 1 oxygen atom bonds with 2 hydrogen atoms to make water. 

Table Numbers

Each element is assigned a number on the periodic table. The number represents the number of protons that atom contains. While hydrogen has 1 proton, copper has 29 protons and gold has 79 protons.

Atomic Weight

The periodic table also contains information about how heavy each element is. The atomic weight is calculated by combining the number of protons and neutrons in the nucleus of the atom.


Each element gets an alphabetic symbol. Many symbols make sense, for example, O is the chemical symbol for oxygen, however some are based on Latin names. The name for gold in Latin is Aurum and its chemical symbol today is Au. 

Where Did They Come From?

The first 5 elements were created during the Big Bang. Heavier elements needed to be made in stars where the huge pressure and high temperatures caused nuclear fusion, forcing lighter elements to fuse together and create new elements. 

Man–made Elements

Scientists started creating new elements in 1939. They do this by colliding existing elements at high speeds. It sounds simple but it’s actually incredibly difficult and uses vast amounts of energy. So far, scientists have created 26 new elements. 

Noble Gases

When scientists classified elements based on the number of protons present, they discovered that elements with a similar number of protons displayed similar properties. The periodic table can be divided into sections based on the properties of the elements. 

Noble gases is 1 way to classify elements. There are 6 noble gases in the universe. They are odorless, colorless, nonflammable, and tasteless. As the atomic number of a noble gas element increases, the abundance of the element decreases.

Helium (He)

Less dense than air, helium has 2 protons. Unlike many of the noble gases, helium cannot be found in the Earth’s atmosphere. Instead it is found under the ground with natural gas. Because it is nonflammable, helium is used to pressurize rocket fuel.

Neon (Ne)

Neon has 10 protons. In 1910 George Claude discovered that when electricity is passed through neon, it gives off a bright red glow. Soon neon lamps were seen in advertising all over the world.

Argon (Ar)

Argon has 18 protons and is used for specialty welding and semiconductor wafer production as well as in light bulbs. An unreactive gas is needed so that the filament inside the light bulb doesn’t burn away.

Krypton (Kr)

Krypton, with 36 protons, is used in very bright lights such as fluorescent bulbs and photography flashbulbs. It allows the filament inside the bulb to reach very high temperatures without burning away. 

Xenon (Xe)

Xenon has 54 protons. Being one of the heaviest noble gases, xenon is used when extremely bright light is needed, such as in lighthouses. Like argon and krypton, it is an unreactive gas that prevents the filament in the bulb from burning away.

Radon (Rn)

Radon is a noble gas that has 86 protons. This radioactive gas releases radiation energy which damages living tissue. Radon occurs naturally in the air and is believed to have helped with evolution, creating occasional mutations in genes.

Hydrogen and Halogens

Hydrogen stands alone on the periodic table, belonging to no group. Halogens, which means salt forming, are a group of elements that form salts when combined with metals. Many of these elements are deadly to humans when in the gas state.

Hydrogen (H)

With a single proton, hydrogen is the universe’s most abundant element, and is essential for life on Earth. Being 14 times lighter than air, hydrogen was used to float airships. After the 1937 Hindenburg disaster, in which the hydrogen caught fire, helium replaced hydrogen.  

Fluorine (F)

Fluorine has 9 protons. Fluorine reacts violently with almost everything, and is so reactive that it earned the nickname “the tiger of chemistry.” Working with fluorine is extremely dangerous and it has caused many accidental explosions and blindings in the laboratory. 

Chlorine (Cl)

When added to water, chlorine and its 17 protons form an acid which kills bacteria as well as many viruses. When chemically bonded to sodium, chlorine forms common table salt. 

Bromine (Br)

With 35 protons, bromine was used in making film as it reacts to light, creating the images that appear in photographs. Bromine is flame–retardant and small amounts are sometimes added to carpets, clothing, and paints.

Iodine (I)

Iodine has 53 protons. Dark purple in color when in its solid form, iodine forms a violet colored gas at its boiling point. When chemically bonded to potassium, iodine is an effective wound disinfectant.

Astatine (At)

Highly radioactive astatine has 85 protons. Berta Karlik was the first person to find Astatine in nature, an extremely difficult feat as it is estimated that only 25 grams of naturally occurring astatine exist on Earth at any one time.

Alkali and Alkaline Earth Metals

Alkali and alkaline earth metals make up the 2 left–hand columns on the periodic table. As the name suggests, these elements are present as metals in their pure form. Alkali metals are metals that are generally unstable, particularly in the presence of water. 

Alkaline earth metals are usually more stable. 

Beryllium (Be)

Beryllium is an alkaline earth metal with 4 protons. It is vital to the aerospace industry as not only is it one of the lightest metals, it also has a high melting point, perfect for constructing spacecraft. 

Strontium (Sr)

The alkaline earth metal strontium has 38 protons. Strontium flakes are added to fireworks and flares to give them a red color. When combined with iron, it can make a magnet.

Calcium (Ca)

Calcium is an alkaline earth metal with 20 protons. One of the most abundant elements found on Earth, it is vital to life on Earth. Calcium is also found in bones, teeth, and shells. 

Potassium (K)

Alkali metal potassium has 19 protons. An abundant element on Earth, it is mainly used for fertilizers. It is essential to life, however potassium is not found in its pure form on Earth because it reacts violently with water. 

Lithium (Li)

Lithium is an alkali metal with 3 protons. Around 30% of all lithium used for industry is used to produce batteries. While excellent at storing energy, it is highly reactive, so it is important to dispose of lithium batteries safely. 

Transition Metals and Metalloids

Transition metals are soft metals that bond readily with other elements. This is due to the electrons present in the 2 outermost shells within the atom. The transition metal group also has the only 3 elements that can create a magnetic field: iron, cobalt, and nickel. 

Not quite metals but also not quite nonmetals, metalloids share properties belonging to both groups. 

Iridium (Ir)

Iridium is a transition metal with 77 protons. It is an excellent metal element to use in spark plugs as it is a noncorroding, hard metal. It also primarily functions as a hardening agent for platinum.

Iron (Fe)

Iron is a transition metal with 26 protons. It is the most common element on Earth (measured by mass) as much of it is located in the Earth’s core. Iron is one of three metals that can be magnetised. 

Vanadium (V)

Vanadium is a transition metal that has 23 protons. It is often added to steel and used in springs due to its excellent shock absorbing properties. A small amount can also increase strength, toughness, and heat resistance.

Molybdenum (Mo)

Transition metal molybdenum has 42 protons. Molybdenum is added to steel to form stainless steel, a metal resistant to corrosion. Other uses include the manufacture of missile and aircraft parts.

Indium (In)

Indium is a metalloid with 49 protons. Indium has only been used commercially for the last 20 years. It is used to coat the surface of LCD screens to conduct electricity away from the front panel.

Bismuth (Bi)

Metalloid bismuth has 83 protons. Bismuth, like other metalloids, has a low melting point, making it ideal for use in heat detecting fire sprinklers. When heat melts the bismuth, it releases a valve that allows water to gush out. 


Nonmetals are usually brittle elements in their solid state. They are good insulators of both heat and electricity, but poor conductors. 

Nonmetals are some of the most plentiful elements in the universe, and they are found in the Earth's crust and atmosphere, as well as in the human body. 

Carbon (C)

Carbon is a nonmetal element with 6 protons. Carbon can form both 1 of the softest natural materials, graphite, and the hardest, diamond. The sixth most abundant element in the universe, it is also found in all forms of life on Earth. 

Phosphorus (P)

Nonmetal element phosphorus has 15 protons. It was discovered in 1669 by Hennig Brand, who tried to isolate a urine compound in order to turn metal into gold. It is found both in the red tip of matches and the strip on the matchbox.

Sulfur (S)

Sulfur is a nonmetal element with 16 protons. Well–known because of its rotten egg smell, it is found naturally around hot springs and volcanoes. Sulfur is used commercially as fuel for flares, in batteries, and as a cleaning agent.

Nitrogen (N)

A nonmetal element with 7 protons, nitrogen in its gas form makes up around 78% of Earth’s air and is nonreactive. In liquid state, nitrogen can be used as a cryogenic, freezing tissue upon contact, as well as for creating smoky effects.

Oxygen (O)

Oxygen is a nonmetal element that has 8 protons. Although it is the gas which humans and other life forms breathe, it’s the most reactive of the nonmetal elements. When oxygen forms a bond with hydrogen, it forms another essential ingredient for life, water. 

Arsenic (As)

Arsenic is a nonmetal element with 33 protons. Renowned throughout history as a deadly poison that causes organ failure, arsenic is both tasteless and odorless, making it easy to add to food. The age of arsenic poisoning ended in 1836 with a detection test. 

Rare Earth Metals (Lanthanides) and Actinide Metals

Unlike what the name suggests, rare earth metals are relatively common. However, these metals bond and diffuse with other minerals very easily, making them difficult to isolate. All actinide metals are radioactive.

Many of the elements in the actinide metal group are also man–made. 

Terbium (Tb)

Terbium is a rare earth metal with 65 protons. A soft metal, terbium is so soft that it can be cut with a knife. As an oxide, terbium is used in fluorescent lights. 

Holmium (Ho)

A rare earth metal with 67 protons, holmium is used in delicate laser surgeries. It has unusual magnetic properties, and when combined with other elements, it gives red or yellow coloring to glass and cubic zirconia.

Praseodymium (Pr)

Praseodymium is a rare earth metal that has 59 protons. It can be used to give industrial glasses a protective, yellow colored coat. It’s also used to make the permanent magnets found in electric motors and generators.

Americium (Am)

Americium is an actinide metal with 95 protons. Created in 1945 by American scientists, it is highly radioactive. A very small amount is used in smoke detectors, as the element reacts to smoke present in the air.

Plutonium (Pu)

Actinide metal plutonium has 94 protons. Plutonium is known as the element, along with uranium, that creates the nuclear bomb. Highly radioactive, it is used to create energy in nuclear power plants. 

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