7. there is 17 electrons, 2 in the first shell, 8 in the second and 7 in the third
There is one electron in sodium's valance shell.
1
14
There are two electrons in the valance shell of helium. Since this is the first shell, it is filled by two electrons.
Eight - it has a full outer shell of electrons.
1
3 valance electrons,13 electrons,13 protons,14 neutrons
Protons won't be found in an electron shell. They are concentrated in the nucleus.
There are 9 protons in the element fluorine.
All atoms are more stable when their outer most electron shell (valance shell also refered to as a valance orbital but it is slightly different) is full of electrons. Non metals generally have almost full valance shells and it takes less energy to gain a few electrons to reach the stable full outer shell than to lose many electrons to form a stable full outer shell. Take F as an example - it has 7 electrosn in its outermost shell and this shell can fit 8. It will accept 1 electron more easily than losing 7.
Hydrogen has one shell with only 1 electron on the valance shell.
There are three valance electrons. These are the electrons in the outer shell if it is not full.