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Noble gases

The noble gases stand in group 18. They have a full outer shell and hardly react, because it costs a lot of energy to break up such a shell. Argon has atomic number 18. In the shell model it is filled as 2, 8 and 8, and the outer shell is full with 8 electrons. Other atoms often react so that they get as many electrons as the nearest noble gas. That is why sodium gives away one electron and chlorine takes up one.

2+8+8=182 + 8 + 8 = 18electrons in argon

Symbols

ArArargon, atomic number 18
group18group 18noble gases

Example

Argon has 18 electrons in a neutral atom.

2+8+8=182 + 8 + 8 = 18, and the outer shell has 8.

Helium is a noble gas too, but it has only the innermost shell, with 2 electrons.
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← Electron shells · Ionic bonding →

Part of Chemistry 1: Atoms and the periodic table.