Ar-40


 * Argon **

Argon's element symbol is Ar. It's one of the six noble gasses shown on the periodic table. Argon is a noble gas because the oxidation number, or the number of electrons the element has to give up before bonding to something else, is 0. This prevents the noble gas from forming compounds. All noble gasses have the maximum number of electrons in their outer shell, causing them to be very stable elements. The atomic number of argon is 18, and the atomic mass is 40. The density of argon is 1.784g/ cm3, causing argon to sink it water. Argon is most commonly used for lighting and light bulbs (refer to Figures 1 and 2). It was discovered in 1894 by Sir William Ramsay. Because of it's location on the periodic table, argon has 18 protons, 22 neutrons. Three shells surround the nucleus of argon, 2 electrons in the first shell, 8 in the second shell, and 8 more electrons in the third shell (refer to Figure 3).

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