Chemistry Of The Chromium Atom

Each Chromium atom has 24 protons in the nucleus and therefore 24 electrons orbiting it when the atom is in its neutral state. Chromium is best known from chromed bumper bars on old cars and Harley Davidson motorcycles.

Aside from it's pure state, Chromium can be found in a startling variety of forms and colors. Some of these have traditionally been used as pigments for paint, with the classic "school bus yellow" being a well known example. Chromium is also important in biological functions and is connected to maintaining healthy blood sugar levels and metabolism of fats in people.

Isotopes of Chromium

There are twenty five known isotopes of Chromium, ranging from 18 to 43 neutrons in the nucleus. Of these there are three non-radioactive types. These are 52-, 53- and 54-Chromium that have 28, 29 and 30 neutrons respectively. The most common is 52-Chromium which makes up about 84% of Chromium atoms.

Electron Arrangement

Chromium is in the d-block of the Periodic Table. This means it has a full outer subshell of two electrons, but has an incompletely filled d-subshell sitting just underneath that filled s-subshell.

Following the standard rules for subshell filling, we end up with the following electron configuration: 1s2 2s2 2p6 3s2 3p6 3d4 4s2.

It's that partially filled subshell that allows Chromium to make such a wide range of colored compounds when it joins with other elements. These are due to its large number of possible oxidation states.

If we look at Chromium's electron arrangement in picture form, it looks like this:

States Of The Chromium Atom

Chromium is never found as an elemental metal in nature. It can be found in any oxidation state from +1 through to +6. These states allow it to form a vast array of compounds. Of these states +3 is the most stable and therefore the most commonly found. Next in stability is the +6 state. Chromium in its +6 state can form some very toxic compounds.

Some examples of various oxidation states for Chromium combined with Oxygen:

+2 state: CrO
+3 state: Cr2O3
+4 state: CrO2
+6 state: Cr2O72- Dichromate ion

Fun Facts For Chromium

The density of Chromium is 7.2 grams per cubic centimeter.

Chromium is so toxic in its +6 oxidation state (also called Chromium VI) that half a teaspoon of one of these compounds could be fatal. Read more about Chromium VI compounds on this Government data sheet.

Chromium Picolinate (a +3 state) is touted as a dietary supplement that will help you lose weight. In reality there is no conclusive proof that this works, though reported side effects of taking this supplement are reduced carbohydrate cravings and improved fat metabolism. Tread with caution though, as taking too much Chromium can have very severe and negative impacts on your health.

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