Valence electrons and main groups – basic principles
How it works
Valence electrons are the electrons on the outermost occupied shell of an atom. The number of valence electrons largely determines the chemical properties of an element, especially how it forms bonds. In the periodic table, the main groups are arranged so that elements in one main group in the main-group elements have the same number of valence electrons. The main-group number in the main groups 1–8 usually corresponds to the number of valence electrons; an important exception is helium in the 8. main group, which has only 2 valence electrons. Noble gases have a full outer shell and are therefore particularly unreactive.
For main-group elements, the main-group number usually indicates the number of valence electrons. Elements of the same main group have the same number of valence electrons and similar chemical properties. Exception: helium is in the 8. main group, but has only 2 valence electrons.
An example
How many valence electrons does an oxygen atom have?
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50 Exercises
To the learning unit →Own explanation and own practice exercises by AmyMath. Subject reference framework: Chemistry. The topic assignment may vary by federal state.