Hydrogen has 1 electron in the first shell (so one valence electron).

The following is a list of total electrons, electrons by shell, and valence electrons for the first 10 elements. You might imagine that, if two atoms bumped into each other, it would be the outer electrons that would interact first. It is only the electrons in the outer-most shell, called the VALENCE shell, that tend to react (be gained, lost, or shared). Notice that there are eight elements in the second row of the periodic table. This means that the second shell can hold a maximum of eight electrons (2+6=8). The 2 s subshell holds a maximum of 2 electrons, and the 2 p subshell holds a maximum of 6 electrons. The second shell has two subshells (labeled 2 s and 2 p). Notice that lithium is the first element in the second row of the periodic table. Therefore the lithium (Li), which has three total electrons, will have two electrons in the first shell and one electron in the second shell. This is why there are two elements in the first row of the periodic table (H & He).īecause the first shell can only hold a maximum of 2 electrons, the third electron must go into the second shell. This first shell has only one subshell (labeled 1s) and can hold a maximum of 2 electrons. The first shell, closest to the nucleus and with the lowest-energy electrons, is shell 1. We use numbers to indicate which shell an electron is in. It is the arrangement of electrons into shells that has the most effect on chemical properties, so we will focus on mainly on shells here. Any s subshell can hold up to 2 electrons p supshell up to 6 electrons d subshell up to 10 and f subshell up to 14. Different subshells hold a different maximum number of electrons.Thus, the first shell has only an s subshell, the second shell has an s and a p subshell, the third shell has s, p, and d subshells, and so forth. The subshells of each shell are labeled, in order, with the letters s, p, d, and f. The first shell has only one subshell, the second shell has two subshells, the third shell has three subshells, and so on. Shells are further divided into subsets of electrons called subshells.Shells do not have specific, fixed distances from the nucleus, but an electron in a higher-energy shell will spend more time farther from the nucleus than does an electron in a lower-energy shell. Generally the higher the energy of a shell, the farther it is (on average) from the nucleus. Electrons are organized according to their energies into sets called shells.We say that the energies of the electrons are quantized.

Electrons in atoms can have only certain specific energies.It makes the following statements about electrons in atoms: The modern theory of electron behavior is called quantum mechanics. Do they move around the nucleus at random, or do they exist in some ordered arrangement?

To describe how electrons are grouped within atoms.Īlthough we have discussed the general arrangement of subatomic particles in atoms, we have said little about how electrons occupy the space about the nucleus.

Valence of carbon periodic table