![]() In the 2nd energy level, we have a p subshell in addition to the s subshell. This specific type of orbital is called the s orbital, and we have 1 s orbital for every s subshell. In the 1st energy level, we have 1 subshell, which basically means we have 1 type of orbital. Each orbital then has 2 electrons, which are said to have different and opposite spins. Finally, within each subshell there are individual orbitals referencing a specific region of space around the atom's nucleus. We can organize these electrons into different subshells based upon the shape of the region they occupy. The pattern that we observe results in 3 classifications as follows (there are other considerations that you will learn about later as well).Ī Shell / Energy Level is a region or set of regions that have the same energy.Īlthough we cannot predict the exact location of the electrons at any time, we can map out the regions of space that they occupy. This pattern continues, but it starts to get more complicated with the inclusion of the d subshell and the transition metal elements beginning after calcium.Īs electrons are added to the space around the atom's nucleus they are arranged in a way as to minimize repulsions. The second electron shell is composed of an s and p subshell which has 4 orbitals altogether which is why period 2 element's valence shell holds 8 electrons. The first shell only has an s subshell which means it only has 1 orbital which is why period 1 elements valence shell only holds 2 electrons. An individual orbital can hold a maximum of 2 electrons.Įach electron shell has a certain amount of subshells (and therefore orbitals and therefore electrons it can hold). s subshells have 1 orbital, p has 3, d has 5, and f has 7. These subshells are themselves composed of orbitals which are the specific orbits of the electrons and each subshell has a certain number of orbitals. And we use the letters s, p, d, and f for subshells. The subshells which compose electron shells describe the general shape of electron's orbit around the nucleus. Electron shells are divided into subshells, which are further divided into orbitals. This is a decent starting point, but later you learn in chemistry that the placement of electrons is more complicated than this. ![]() And so if I'm understanding it correctly. Elements in period 2 (building on the previous 2 electrons) need 8 more electrons to fill the second electron shell which is their valence shell. So elements in period 1 (hydrogen and helium) need 2 electrons to fill their valence shell. Elements in each column have the same valence shell electron configurations, and the elements have some similar chemical properties.So you're 2,8,8,2 rule looks like it shows the maximum amount of valence electrons elements can have in a period up to atomic number 20 (calcium). The same concept applies to the other columns of the periodic table. The organization of electrons in atoms explains not only the shape of the periodic table, but also the fact that elements in the same column of the periodic table have similar chemistry. Because much of the chemistry of an element is influenced by valence electrons, we would expect that these elements would have similar chemistry- and they do. They all have a similar electron configuration in their valence shells: a single s electron. Their electron configurations (abbreviated for the larger atoms) are as follows, with the valence shell electron configuration highlighted: Electrons, electron configurations, and the valence shell electron configuration highlighted. For example, take the elements in the first column of the periodic table: H, Li, Na, K, Rb, and Cs. If we look at just the valence shell’s electron configuration, we find that in each column, the valence shell’s electron configuration is the same. (The inner electrons are called core electrons.) The valence electrons largely control the chemistry of an atom. The electrons in the highest-numbered shell, plus any electrons in the last unfilled subshell, are called valence electrons the highest-numbered shell is called the valence shell. ![]() The periodic table is separated into blocks depending on which subshell is being filled for the atoms that belong in that section.
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