Sizes of Atomic Orbitals

Concepts

The size of a given orbital is primarily determined by the principal quantum number (n). The electrons in an atom can be viewed as residing in shells, the size of which is established by the principal quantum number.

n Shell radius
(angstroms)
Nbr. Electrons
1 K 1.4 2
2 L 4.8 8
3 M 10.3 18
4 N 17.8 32

The third column of this table lists the radius of the isosurface for the corresponding s orbital containing 90% of the electron density.

As the size of the shell grows, the total number of electrons that can reside in the shell also increases.



Exercise

Answer the following questions by examining various orbitals in the display shown below.

1. Observe the sizes of the orbitals for a series of values of n and the same value of l. How does the size of the orbital vary as n increases?

2. Observe the sizes of the orbitals for a series of values of l and the same value of n. How does the size of the orbital vary as l increases?

3. Suppose an atom contains electrons in the K, L, M, and N shells. If another atom approaches, with which shell will interaction first occur? (In other words, which shell in the first atom extends furtherest from the nucleus?)

4. Is it acceptable to ignore f orbitals in modeling chemical bonding, even if electrons reside in these orbitals? Why or why not?

5. If an atom contains electrons in the K and L shells, is it necessary to consider the K shell electrons when modeling chemical bonding? Why or why not?







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