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MCAT Chemistry Question

What is the azimuthal quantum number (l) for the orbital to which a fluorine atom gains an electron to form an F- ion?

A.    0

B.    1

C.    2

D.    3

Click for Explanation

The azimuthal quantum number (also known as the orbital quantum number or angular momentum quantum number), l, designates the subshell of an atom and gives the “shape” of an orbital. The number also indicates the number of angular nodes, or regions of zero probability, within the orbital.

The orbital shapes commonly referred to as s, p, d, and f, correspond to azimuthal quantum numbers of 0, 1, 2, and 3, respectively.

The electron configuration for elemental fluorine is 1s22s22p5. When fluorine gains an electron to become F, the electron adds to the p orbital. P orbitals are dumbbell shaped with one angular node and correspond to an azimuthal quantum number of 1, making B the correct answer.

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