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Atomic Orbitals

Orbitals are mathematically derived regions of space with different probabilities of finding an electron.  There are four different kinds of orbitals, denoted s, p, d, and f each with a different shape. Of the four, the s and p orbitals are the most important to organic and biological chemistry.

s Orbitals

An s orbital is spherical with the nucleus at its center.

Action
  • Successively click on the 1s, 2s, and then 3s radio buttons.  What do you notice about the size of the s orbitals?
  • The probability of finding an electron in an s orbital looks like a sphere having the nucleus as its center.  In two dimensions it looks like a circle.
  • We can say that s-orbitals are "spherically symmetric" having the probability of finding the electron at a given distance equal in all the directions.
  • The size of the s orbital increases with the row or shell number (i.e. principal quantum number (n)).   Thus, 4s > 3s> 2s > 1s.

p Orbitals

A p orbital is dumbbell-shaped.

Action
  • Click on one of the 2p orbitals buttons.  Notice the dumbbell shape?

This implies that the electrons are located above and below the atom for each of the three p orbitals.

d Orbitals

Four of the d orbitals are cloverleaf-shaped. The fifth d orbital is shaped like an elongated dumbbell with a doughnut around its middle.  The d orbitals are important in transition metal and organometallic chemistry.

Take Note
  • Orbitals represent a volume of space within which an electron would have a certain probability of being based on particular energy states and atoms
  • s orbitals are centered around the nucleus and therefore the electrons in them are closer to the nucleus.
  • s orbitals are lower in energy (more stable) than p orbitals in the same row.
  • p orbitals have two lobes that project away from the nucleus.  Electrons in p orbitals spend more time further away from the nucleus than s electrons.