- The charge on
a monoatomic anion depends on the group for the atom. Nonmetal elements
have greater attractions for electrons and tend to gain electrons
to form anions. The charge on the ion is written as a superscript
after the element symbol. For example chlorine gains one electron
to form chloride, Cl1-. Sulfur gains two electrons to form
sulfide, S2-.
-
- You can predict
the negative charge on an anion by looking at the group number for
the atom. The charge for representative
elements is typically equal to the group number minus eight.
-
- Example:
Fluorine,
F, is in group 7A. The negative charge is 7 - 8 = -1. The symbol is
F1- with the charge written as a superscript.
-
- Example:
Oxygen,
O, is in group 6A. The negative charge is 6 - 8 = -2. The symbol is
O2- with the charge written as a superscript.
|
- The charge on
a monoatomic cation like sodium ion, Na1+, depends on the group for the atom, Group 1A for sodium.
-
- Metal elements
have weaker attractions for electrons than the nonmetals. Atoms of
metals can be stripped of electrons to form cations. You can predict
the positive charge on cations using the group number for representative elements.
-
- Example:
-
-
Sodium, Na, is in group 1A. It loses one electron to form the sodium
ion, Na1+.
-
The charge is written after the symbol as a
superscript.
-
- Example:
- Barium, Ba, is in group 2A. Barium loses two electrons to form the
calcium ion, Ba2+.
-
- Example:
- Aluminum, Al, is in group 3A. Aluminum loses three electrons to form the aluminum ion, Al3+.
|
Exercise: What
charge do you predict for magnesium, Mg, in group 2A? |
Exercise: Which
of the following would you predict to form a cation with a
charge of +1? |
Revised
by Dr. Walt Volland
July 8, 2013 All rights reserved.