The valence electrons are the electrons found in the last energy level, that is, those that are farthest away from the nucleus of the atom. They are very important because these electrons are the ones that allow chemical bonds, either because they are transferred to another atom or they are shared.
The Lewis structure shows the valence electrons represented by dots or crosses. In this example, they are represented by dots.
We see that the atom Al, aluminum, has three dots. Therefore, it has three valence electrons.
The Bohr model gives us more information about the atom, it is a way of representing how the electrons are distributed around the nucleus. We can see in this model all the energy levels.
The energy levels are represented by circles around the nucleus, the dots on the circles represent the electrons. And the farthest circle is the last energy level. The dots on this circle will be the valence electrons.
If we count the dots in the farthest circle we see that there are 6, this means that this element has 6 valence electrons.
So the answer will be:
3 valence electrons in Lewis dot structure
6 valence electrons in the Bohr model