Untitled - Kelly Walsh High School

110 CHEMISTRY FOR THE UTTERLY CONFUSED
Schrödinger’s equation required the use of quantum numbers to describe each
electron within an atom corresponding to the orbital size, shape, and orientation
in space. Later it was found that one needed a quantum number associated
with the electron spin.
DeBroglie, in the mid 1920s, proposed the idea that particles could be treated
as waves by the relationship, h/mv. This equation related the mass (m) and
velocity (v) of a particle to its wavelength () by using Planck’s constant (h).
7-4 Quantum Numbers and Orbitals
Quick Tip
The first quantum number is the principle quantum number (n) that describes
the size of the orbital and relative distance from the nucleus. The possible values
of n are positive integers (1, 2, 3, 4, and so on). The smaller the value of n,
the lower the energy, and the closer the orbital is to the nucleus. We sometimes
refer to the principle quantum number as designating the shell the electron is
occupying.
Each shell contains one or more subshells, each with one or more orbitals. The
second quantum number is the angular momentum quantum number (l) that
describes the shape of the orbitals. Its value is related to the principle quantum
number and has allowed values of 0 to (n1). For example, if n 4, then the
possible values of l would be 0, 1, 2, and 3 ( 41).
• If l 0, then the orbital is called an s-orbital and has a spherical shape with
the nucleus at the center of the sphere. The greater the value of n, the larger
the sphere.
• If l 1, then the orbital is called a p-orbital with two lobes of high electron
density on either side of the nucleus, for an hourglass or dumbbell shape.
• If l 2, then the orbital is a d-orbital with a variety of shapes.
• If l 3, then the orbital is an f-orbital with more complex shapes.
Check your textbook for pictures of some or all of the orbitals.