Key idea
Valence electrons
Valence electrons are the electrons most directly involved in bonding and chemical reactivity, although the exact boundary between valence and core can depend on context.
Valence electrons
The key idea
Valence electrons are the electrons most directly involved in bonding and chemical reactivity, although the exact boundary between valence and core can depend on context.
Why it matters
For main-group elements they provide a simple route to periodic similarities; transition metals require more care.
A picture to remember
Key idea
Valence electrons
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Guided example
Valence electrons
Valence electrons are the electrons most directly involved in bonding and chemical reactivity, although the exact boundary between valence and core can depend on context.
Put it into practice
Valence electrons
Choose a concrete case linked to Valence electrons. Write down the known information, what you are trying to find, and the units. Then state the rule, model or trend you will use. If a calculation is involved, keep the units visible at every line; if it is conceptual, state what changes and what remains fixed.
Check your answer
A strong answer contains four things: the starting situation, the variable that changes, the direction or numerical result, and one check. The check can be a unit, an order of magnitude, a limiting case or a comparison with a familiar example.