PS-2.5 Predict the charge that a representative element will acquire according to the arrangement of electrons in its outer energy level.
Key Concepts: ion
By definition, an ion is an electrically charged atom or group of atoms. Ions that carry a positive charge are called cations, and atoms that carry a negative charge are referred to as anions. In the ground state ( lowest energy state,) atoms have the same number of electrons as protons. This equality of + and - charge mean that under natural conditions, atoms are electrically neutral. However, if an atom does not have the same number of electrons as protons, then the atom will carry a + or - electrical charge, and it will be an ion. Under certain conditions atoms can gain or lose valence electrons to become either a negative or positive ion. If an atom gains valence electrons it will be a negatively charged ion, or anion, because it will have more -Electrons than +Protons. If an atom loses valence electrons it will become a positively charged ion, or cation, because it will have fewer -Electrons than +Protons. Even though atoms can become electrically charged, they are still atoms of the same element. A Lithium atom with a net charge of +1 is still a Lithium atom. A Fluorine atom with a net charge -1 is still an atom of the element Fluorine.
A Boron atom becomes a 3+ cation. A Fluorine atom becomes a 1- anion.
The chart below shows common electrical trends on the periodic table.
ELECTRON TENDENCY AND ION CHARGE
ELECTRON DOT DIAGRAM
Atoms lose 1 valence electron to become 1+ ions
Atoms lose 2 valence electrons to become 2+ ions
Alkali Earth Metals
The Transition Metals in groups 3 through 12 are not shown here.
Most can lose 1,2,or 3 valence electrons to become 1+, 2+, or 3+ ions respectively.
Atoms lose 3 valence electrons to become 3+ ions
Atoms can lose or gain 4 valence electrons to become 4+ or 4-ions
4+ OR 4-
Atoms gain 3 valence electrons to become 3- ions
Atoms gain 2 valence electrons to become 2- ions
Atoms gain 1 valence electron to become 1- ions
Atoms are stable with 8 valence electrons...Except for Helium. It is stable with a filled first level containing 2 valence electrons. These elements are stable. Their valence level is filled.
Watch the video lesson on electron configurations: Part 1 part 2 part 3