Chem – Orbitals


What are orbitals?

VIDEO Explanation of orbitals.

If you look deeper into the paths that the electrons take around the nucleus of an atom you actually begin to see that some of the shapes are not circular or spherical like the Bohr model suggests. Therefore, the Bohr model we have been working with so far is not the complete story of how electrons travel around the nucleus. Because Bohr studied the hydrogen atom and because the most common paths that the electrons take in a hydrogen atom are spherical, it is understandable that he missed the other more oddly shaped electron paths. Although Bohr’s work was groundbreaking and brilliant, we now have a better picture of the electron paths around the atom. Instead of calling them shells we now refer to the paths that the electrons take as orbitals. The first type of orbital is the S orbital. S stands for spherical and these are the orbitals that Bohr discovered. However, the other orbitals tend to be dumbbell shaped. Those orbitals include the P, D, and F. The F orbitals also have some strange doughnut shaped orbitals. It is not very important to know the shapes of the different orbitals, but it is good to know that they have different shapes.


The two most important aspects of the orbitals are to be able to spot the orbitals on the periodic table and to know how many electrons are in each orbital set. Because of the organization of the periodic table, you can also find where the different orbitals are. The periodic table orbitals is a good link to view as you read this these next sentences. There is also an alternative way to look at the orbitals on the periodic table with this link (shifted). The first set of orbitals is the S orbitals. The S orbitals are the first two columns of the periodic table that start with Hydrogen and Lithium. Helium is also part of the S orbitals even though it is on the right side of the periodic table. This means that the last electron in hydrogen and helium travels around the atom in an S orbital shape. If we count through the rows of the periodic table we notice that each row contains only two elements in the S orbitals. That means the S orbitals can carry a maximum of 2 electrons.


The next orbitals are the P orbitals. The P orbitals start on the second row of the periodic table with boron and carbon. The P orbitals continue all the way to the element neon in the second row of the periodic table. If we count across that row from boron to neon we find that each P orbital set contains a maximum of 6 electrons. All elements below the columns that start with boron, carbon, nitrogen, oxygen, fluorine, and neon are considered to have their last electron in the P orbitals. D orbitals roughly follow the transition metals. On the fourth row of the periodic table the D orbitals start with scandium and end with zinc. If we count across from scandium to zinc, we discover that the D orbitals contain a maximum of 10 electrons. The D orbitals are all those columns between and including scandium and zinc. The final orbitals shown on the periodic table are the F orbitals. The F orbitals are the separated elements down at the bottom of the periodic table. The top row of the F orbitals begins with Lanthanum and ends with Ytterbium. The F orbitals are also the next row below cerium and lutetium. If we count across from cerium to lutetium, we learn that the F orbitals contain a maximum of 14 electrons.


You should have a basic understanding of how the first few orbitals fit together into a picture. VIDEO to show you how to draw the first few orbitals.


Examples: The last electron of each element is in what type of orbital? Use the periodic table orbitals link as you are analyzing these examples.  If you need to, use the The periodic table orbitals.

Element Orbital Type
C p
Sr s
U f
Ni d
Sn p


PRACTICE PROBLEMS: The last electron of each element is in what type of orbital?  Try using a regular periodic table to solve these.  Try NOT to use the The periodic table orbitals.

Element Orbital Type
Fe d
He s
Al p
Pu f
Xe p
K s
Hg d


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