The amount of electrons. Electrons fill according to occupying the lowest energy state, and also by not spin pairing until each suborbital of same energy has one electron in each. Beware when entering the d orbitals, i.e. Cr and Cu, they will prefer to fill 4s1,3d5 and 4s1,3d10 respectively as this is more satisfying in being the lowest energy state.
it depends on the number of electrons.
If all the electron orbitals are filled then the atom is inert. It will not chemically react with anything. If an atom has empty spaces in the outer orbit, it will react with other elements. Electrons from other elements can share positions in the outer orbits.
The energy levels of an atom hold electrons.
You appear to mean silicon. Please see the link.
valence electrons
An atom has multiple energy levels. When an atom has more electrons than it can fit into an energy level, then it puts them into the next higher energy level.
the one that is completely filled
What is the neutral atom that has its first two energy levels filled, has 5 electrons in its third energy level, and has no other electrons? Enter the name of the element, not the abbreviation.
Neon has the 1s2, 2s2, and 2p6 levels filled.
1s2 2s2 2p6 3s2 3p3
The first 3 energy levels are filled, the 4s and 4p and 4d sublevels are filled, and the 5s and 5p sublevels are also filled. So only the first three energy levels are completely filled. The fourth and fifth energy levels are partly filled. The electron configuration is 1s22s22p63s23p63d104s24p64d105s25p6 or [Kr]4d105s25p6.
Sodium
If all the electron orbitals are filled then the atom is inert. It will not chemically react with anything. If an atom has empty spaces in the outer orbit, it will react with other elements. Electrons from other elements can share positions in the outer orbits.
The energy levels of an atom hold electrons.
You appear to mean silicon. Please see the link.
The Third
Phosphorus, I think. Please see the link.
energy