| Themes > Science > Chemistry > General Chemistry > Atomic Structure > Electronic Structures of Atoms > Atomic Structure Index > Ions |
The Electrons of an atom exist in a cloud around the nucleus. In a neutral atom there are as many electrons as there are protons. Adding or subtracting an electron creates an ion of that atom. This is denoted by placing a trailing superscript with the charge on the atomic symbol. For example, an atom of lithium that lost an electron would have a +1 charge and a symbol Li+ An ion with a positive charge is known as a cation, one with a negative charge is known as an anion. Example: How many electrons does the Al+3 ion have? Solution: A neutral atom has the same number of protons as electrons. Looking in the periodic table, aluminum has 13 protons and thus 13 electrons as a neutral atom. Since it has a +3 charge, this means 3 electrons are missing, so Al+3 has 10 electrons. |
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