There is a total of 8 electrons that are needed to fill outer shell of most atoms. An atom is the smallest unit of matter.
8
the electrons on their outer shell, all atoms want to gain a full valence shell.
there are four electrons on the outer shell of carbon..
Only two electrons.
These are the valence electrons.
It depends, most atoms need 8 total valence electrons in their outer shell (some need 2). So subtract the number they have (determined by the group that the element is in) from 8 and that is how many they need to fill their outer shell!
Valence Electrons
Only valence electrons.
The most stable electron configuration for any atom is to have a complete outer shell. For the smallest atoms, that can be no electrons at all (for H+) since no shell is equivalent to a complete shell, or just two electrons in the outer shell, such as for a helium atom, but for most elements that means 8 electrons in the outer shell. We then have atoms which have five or more electrons in their outer shell and therefore need three or less to complete their shell, and they tend to gain electrons because it is easier to gain three than it is to lose five. Similarly, there are atoms with three or fewer electrons in their outer shell, and they tend to lose electrons because it is easier to lose three than it is to gain five. In the middle we have an atom such as carbon, with four electrons it its outer shell; it can gain or lose electrons with equal ease.
The number of electrons in the outer shell are called Valence electrons and are important in determining how the atom reacts chemically with other atoms.
Atoms often form ions by losing or gaining enough electrons to end up with a full outer shell. How many electrons are in a full outer shell for most atoms? Don't know? How about Googling full outer shell?
It depends on the number of electrons in the outer valence shell in the atom