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The Element Sulfur: Structure and Chemical Properties

The element Sulfur contains 16 protons in its nucleus and therefore has 16 electrons in its neutral state. Sulfur can be found in its pure form in nature and also occurs in a wide variety of states where it is combined with a range of different metals. Sulfur has many important applications. It is used in the vulcanization of rubber and also in production of Sulfuric Acid. This chemical is central to many important industries including the production of fertilizers.

Sulfur is also present in oil deposits and when it is burned it produces sulfur dioxide which can lead to acid rain.

Isotopes Of The Element Sulfur

Unlike lighter elements Sulfur has four naturally occurring and stable isotopes. These are 32- 33- 34- and 36-Sulfur which contain 16, 17, 8 and 20 neutrons respectively. The full range of isotopes is from 26-Sulfur to 49-Sulfur, but all except the four stated above are radioactive and have short half lives.

Of the stable isotopes the most common is 32-Sulfur, and it is this isotope that is shown in the Bohr diagram to the right. Over 95% of any Sulfur sample will be made of 32-Sulfur atoms. The next most common is 34-Sulfur with a little over 4% representation. The other two isotopes make up the rest.

Electron Structure Of The Element Sulfur

sulfur facts Sulfur's 16 electrons give us the electron details of 1s2 2s2 2p6 3s2 3p4 for an outer shell electron count of 6. These 6 electrons are arranged in the four quarters around the atom to give the electron dot diagram shown to the left. The placement of the electrons in relative energy positions is shown below. Because of this Sulfur requires two additional electrons to obtain a full outer shell. It can either share these through covalent bonds with other elements or it can absorb two free electrons to become the negatively charged ion S2-.

best sulfur products

Sulfur has the same electron dot structure as oxygen and it behaves in a similar fashion. For example, rotten egg gas is H2S, the same as H2O but using a Sulfur atom instead of Oxygen.

sulfur dioxide structure

It is worth noting that H2O and H2S are not chemically identical. Though Sulfur and Oxygen behave in the same way, Oxygen's outer shell is much closer to the nucleus than is Sulfur's. This accounts for the differences in electronegativity values of the elements; Oxygen is 3.5 whereas Sulfur rates a poor (by comparison) value of 2.5. This also means that when Sulfur is sharing electrons, it pulls those electrons toward it less than Oxygen does which affects the chemical properties of the compounds. The technical way to say this is that oxygen forms polar covalent bonds whereas Sulfur tends to form non-polar covalent bonds.

Allotropes Of The Element Sulfur

Sulfur occurs in several naturally occurring allotropes, or structures, and many more again have been produced artificially. Typically Sulfur atoms are formed into rings with each atom bonded to two others covalently. This arrangement satisfies all Sulfur atoms involved as they all obtain the stable full outer shell of 8 electrons.

The most common sulfur ring is S8, with 8 atoms joined together. Below is a picture of it in 2D, then a 3D representation that takes into account the real life shaping of molecules using the vsepr theory. Naturally occurring Sulfur is mainly S8, but also has small amounts of S7 and S6 in it.

sulfur molecule

This image also serves to show the value of the 2-D representations of molecules. The left side diagram is far simpler to understand and to identify the bonding in. The right hand version of the Sulfur ring is the actual structure.

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