and an example for valency electron.
For example: oxygen
The electronic configuration of oxygen is 1s2
. There are two core electrons that are in the atomic orbital 1s. There are six valence electrons that are in the atomic orbitals 2s and 2p.
Electrons in atoms are distributed in layers. The more electrons an atom has, the more layers there are.
As you pile up electron layers, the electrons that are closer to the atom nucleus are buried under the successive layers --> they can't react anymore to form bonds. They are core electrons.
Valence electrons are the one on top of the pile, which are accessible to form bonds and molecules...
What about these?
Cs, Fr: Valence 3, should be 1..
F: 1, Cl: 5, should be 7..
Some of this doesn't make sense..
Where did you get those numbers from? Some of them are wrong. And it looks like they refer to the number of unpaired electrons, and not to the number of valence electrons.
Cs and Fr have only 1 valence electron each. They can easily give it away to form Cs+
, which have electronic configurations similar to related noble gases. Cs+
are more inert.
F and Cl have 7 valence electrons. They are just missing 1 electrons to fulfil their orbitals and form F-
Oxygen has 6 valence electrons. It has 2 unpaired electrons which are available to form 2 bonds.
Nitrogen has 5 valence electrons. It has 3 unpaired electrons ready to form 3 bonds.