Barrons SAT Subject Test Chemistry, 13th Edition

Noble

Gas

Electron Distribution

Electrons in Valence Energy

Level

Helium

1 s^2

2

Neon

1 s^2 2 s^2 2 p^6

8

Argon

1 s^2 2 s^2 2 p^6 3 s^2 3 p^6

8

Krypton

1 s^2 2 s^2 2 p^6 3 s^2 3 p^6 3 d^10 4 s^2 4 p^6

8

Xenon

1 s^2 2 s^2 2 p^6 3 s^2 3 p^6 3 d^10 4 s^2 4 p^6 4 d^10 5 s^2 5 p^6

8

Radon

1 s^2 2 s^2 2 p^6 3 s^2 3 p^6 3 d^10 4 s^2 4 p^6 4 d^10 4 f^14 5 s^2 5 p^6 5 d^10 6 s^2

6 p^6

8

TIP

Notice the recurrence of the octet (8) of electrons in noble gases.

The distinguishing factor in these very stable configurations is the
arrangement of two s electrons and six p electrons in the valence energy level in
five of the six atoms. (Note that helium, He, has only a single s valence energy
level, which is filled with two electrons, making He a very stable atom.) This
arrangement is called a stable octet. All other elements, other than the noble
gases, have one to seven electrons in their outer energy levels. These elements are
reactive to varying degrees. When they do react to form chemical bonds, usually
the electrons shift in such a way that stable octets form. In other words, in bond
formation, atoms usually attain the stable electron structure of one of the noble
gases. The type of bond formed is directly related to whether this structure is
achieved by gaining, losing, or sharing electrons.

TYPES OF BONDS

Ionic Bonds

When the electronegativity values of two kinds of atoms differ by 1.7 or more
(especially differences greater than 1.7), the more electronegative atom will
borrow the electrons it needs to fill its energy level, and the other atom will lend
electrons until it, too, has a complete energy level. Because of this exchange, the
borrower becomes negatively charged and is called an anion; the lender becomes