How many electrons can the first shell hold?
Quick Answer
The first electron shell can hold 2 electrons. Once it is full, the atom is especially stable.
The Full Story
The first shell of an atom can hold a maximum of 2 electrons. This is why hydrogen, with one electron, is one electron short of stability, while helium has a full first shell and is chemically very unreactive. The idea comes from quantum mechanics, where electrons occupy energy levels rather than simple planetary-style paths. Shell capacities help explain the structure of the periodic table and why elements in the same group behave similarly. The first shell is the smallest and simplest example of electron arrangement in atoms.
Key Facts
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