Chalcogens- On the Periodic Table

Core Concepts

In this tutorial you will learn about the Chalcogens family on the periodic table, as well as their unique characteristics.

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Chalcogens on the Periodic Table

Chalcogens are elements that belong to group 16 on the periodic table. There are five elements that can be classified as chalcogens: oxygen, sulfur, selenium, tellurium, and polonium. Some scientists consider livermorium to be a member of the chalcogens as well. It is sometimes common for oxygen to be excluded from the chalcogen family. This is because oxygen’s characteristics differ a bit among the other elements in the family.

Each element in the chalcogen family have 6 electrons in the valence shell. These family of elements derived their name from the greek word “chalcos”, which means ore-forming, since each of these elements are found in copper ores and in sulfides and oxides in the Earth’s crust. Most of the chalcogens have more than one allotrope, the existence of a chemical element in two or more forms. For example sulfur has over 20 allotropes and oxygen is known to have about 9.

simple periodic table with atomic number

Electron Configuration for Chalcogens

Generally the electron configuration for chalcogens is ns²np⁴. The electron configuration for livermorium, which is not displayed in the chart, is [Rn]5f¹⁴6d¹⁰7s²7p.

Chalcogen	Electron Configuration
Polonium (Po)	[Xe]4f¹⁴5d¹⁰6s²6p⁴
Sulfur (S)	[Ne]3s²3p⁴
Selenium (Se)	[Ar]3d¹⁰4s²4p⁴
Tellurium (Te)	[Kr]4d¹⁰5s²5p⁴
Oxygen (O)	[He]2s²2p⁴

*Note that “n” denotes the value of the principal quantum number.

Atomic and Ionic Radius of the Group 16 Elements

Both the atomic and ionic radius of the elements in the chalcogen family are smaller than those of the group preceding them, group 15. This is because of the increased effective nuclear charge, the greater attraction of the electrons to the nucleus of the atom decrease radius size. As expected, based on atomic and ionic radius trends on the periodic table, the radius of the chalcogens increase when we move down a group. So, the chalcogen with the smallest atomic radius and ionic radius is oxygen. The chalcogen with the largest atomic and ionic radius is polonium.

Melting and Boiling Points

Since there is an increase in atomic size and masses when we move down a group on the periodic table, the melting and boiling points of these elements will have a direct correlation. This is because as we move down a group the magnitude of van der waals forces also increases. So, oxygen is known to have the lowest melting and boiling point.

Ionization Energies

When the radius or size of an atom increases, the ionization energy decreases. This is because the greater the distance the electrons in the valence shell are from the nucleus the less forces of attraction the nucleus has on these electrons. So, elements smaller in size will often have higher ionization energies than elements with larger size. Because of this the ionization energy’s of the chalcogens decrease as we move down in the group. Oxygen is known to have the highest ionization energy among the family. It might also be important to note that as we move across a period on the periodic table ionization energy increases. Therefore, oxygen has a higher ionization energy than an element like lithium.

Reactions Between the Group 16 Elements

When the chalcogens react with dihydrogen (H₂), they will usually form hydrides with the formula H₂X. X denotes any of the chalcogens: oxygen, sulfur, selenium, tellurium, or polonium.

X (chalcogen) + H₂ (dihydrogen) → H₂X (hydride of the chalcogen)

Characteristics of Group 16

Oxygen

Configuration: 1s²2s²2p⁴
Oxygen works to from rust through oxidation, and is well known to react with other atoms.
Oxygen is the least dense out of all of the chalcogens with a density of 0.00143 g/cm³.
At room temperature oxygen is in a gaseous state and it is colorless, odorless, and tasteless.
It reaches its boiling point around -297.31 degrees F.

Polonium

Polonium is the largest of all the chalcogens with 2, 8, 18, 32, 18, and 6 electrons in the shells.
Its configuration is 1s²2s²p⁶3s²p⁶d¹⁰4s²p⁶d¹⁰f¹⁴5s²p⁶d¹⁰6s²p⁴.
Polonium has the highest density, with a density of 9.196 g/cm³.
Polonium is an exception to the rule of boiling point increasing with atomic weight, as its boiling point is lower than tellurium at 1764 degrees F.
33 different isotopes of this element can be found on Earth.

Tellurium

The electron configuration for tellurium is 1s²2s²p⁶3s²p⁶d¹⁰4s²p⁶d¹⁰5s²p⁴.
Tellurium has the highest boiling point out of all of the chalcogens at 1810 degrees F.
It is naturally found as a silver mettaloid when it is in its crystalline form.

Selenium

Selenium’s electron configuration is 1s²2s²p⁶3s²p⁶d¹⁰4s²p⁴.
Although selenium is a non-metal, it can conduct electricity.
Selenium’s boiling point is also very high at 1265 degrees F.
It is naturally found as a reddish powder, but when it is processed it turns black.
Selenium is photo-conductive, making it electrically charged when it is exposed to light.

Sulfur

The electron configuration of sulfur is 1s²2s²p⁶3s²p⁴.
Sulfur has a large range of oxidation states ranging from -2 to +6.
This element is found in trace amounts in the Earth’s crust and the human body.
Sulfur is a yellow solid, and produces a rotten smell when it gets burned.