Atoms form ions by gaining or losing electrons to achieve a full outer electron shell like noble gases. Ions then bond to form ionic compounds between metals and nonmetals like NaCl. Covalent bonds form when atoms share electrons to achieve full outer shells, like in H2O. Polyatomic ions, which are ions of two or more bonded atoms, can also participate in ionic bonding, such as Ca(OH)2 which contains hydroxide ions bonding to calcium ions. The number of each type of atom in a compound is shown by subscripts based on the ions formed.

1. Atoms

2. Vocabulary
● Ion
● Valence Electrons
● Electron Orbitals
● Neutral Atom
● Chemical Bond
● Ionic Bond
● Covalent Bond
● Polar Covalent Bond
● Nonpolar Covalent Bond
● Polyatomic Ion
● Electronegativity
● Molecule
● Double Bond
● Triple Bond

3. Chemical Bonds

7. All elements want to have a complete set of valence electrons; elements will react until they
have a complete set. A complete set consists of eight electrons, this explains why Noble gases do
not react. Helium is a Noble gas, even though its outer shell only has two electrons. Helium outer
shell only accepts two electrons, therefore its set of valence electrons is complete; it will not react.

8. ***Pg 58 & 59

10. IONS

11. Ions
Atoms may lose or gain electrons in order to have a complete outer shell.
When an element loses an electron(-), it becomes positively charged. This is
because it now has more protons (+) than electrons (-).
Conversely, when an element gains an electron(-), it becomes negatively
charged. This is because it now has more electrons (-) than protons (+) .

12. Valence Electrons & Ions
The number of electrons lost, or
gained, depends on the valence
electrons of the element. (The
outer shell)
Sodium has one valence electron(outer
shell), and the shell beneath has eight. If it
loses the one valence electron, the shell
underneath becomes the outer shell with
eight electrons.
The same concept applies to Magnesium.
The difference is that Magnesium has two
valence electrons.

13. Natural Ions
Atoms may lose or gain electrons in order to have a complete outer shell.
When an element loses an electron(-), it becomes positively charged. This is
because it now has more protons (+) than electrons (-). (METALS)
Conversely, when an element gains an electron(-), it becomes negatively charged.
This is because it now has more electrons (-) than protons (+) . (NONMETALS)

14. Valence Electrons & Natural Ions
Atoms may lose or gain electrons in order to have a complete outer shell.
In summary, the ion that an atom forms depends on its valence electrons
*(Identifiable by the atoms group number).

15. Chemical Bonds: Ionic

16. ●Metal + Nonmetal
○Na + Cl NaCl (Chemical Change? Pure Substance?)
■ Sodium (*Metal) losses an electron and become a cation Na+
■ Calcium (Nonmetal) gains an election and becomes an anion Cl-
■ These changes allow both Na and Cl to have 8 electrons in
their outermost shells
Ionic Bonds

18. Draw Lewis Dot Structure
CaF2 :
BeF2
Natural Ions Be, F ?
Draw the Lewis Dot Structure of the
following Ionic Bonds:

19. The subscripts following each element’s symbol represent how many
atoms of that element are present in the molecule formed.
Subscripts
In the molecule BeF2 , there is one
Beryllium atom and two Fluorine atoms.
You can determine the subscripts by
exchanging them with the superscripts of
the natural ions of the elements involved.
Natural Ions Chemical Formula
Be2+ F1- BeF2

20. A polyatomic ion is an ion formed with two or more atoms.
When a covalent bond (Two or more Nonmetals) forms, and the
resulting number of electrons and protons is not equal, an ion with two or
more atoms is formed.
Polyatomic Ions
(OH)- (CN)-
(NH4)+

21. Polyatomic Ions
Polyatomic
Ion
Hydroxide
Protons (+) 6 (O) + 1 (H) = 7+
Electrons (-) 6(O) + 1 (H) + 1 (?) = 8-
Charge 1-
Once polyatomic ions have formed, they “act” as one atom and form ionic bonds with metals.
**Ionic bonds with polyatomic ions work the same way as ionic bonds between metals and
nonmetals.

22. Polyatomic Ions
Polyatomic
Ion
Cyanide
Protons (+) 4 (C ) + 1 (N) = 5+
Electrons (-) 4 (C ) + 5 (N) + 1 (?) = 10-
Charge 3-
Once polyatomic ions have formed, they “act” as one atom and form ionic bonds with metals.
**Ionic bonds with polyatomic ions work the same way as ionic bonds between metals and
nonmetals.

23. Polyatomic Ions
Polyatomic
Ion
Ammonium
Protons (+) 5(N) + 4 (H) = 9+
Electrons (-) 5(N) + 3 (H) = 8-
Charge 1+
Once polyatomic ions have formed, they “act” as one atom and form ionic bonds with metals.
**Ionic bonds with polyatomic ions work the same way as ionic bonds between metals and
nonmetals.

24. **Like “regular” ionic bonds, the number of atoms present and the
combination in ionic bonds with polyatomic ions depends on the type of
ion each atom and polyatomic molecule forms.

25. K(NO3)
Ionic Bonds with Polyatomic Ions
K+
(NO3)-
I
O
N
S

26. Ca(OH)2
Ionic Bonds with Polyatomic Ions
Ca2+
(OH)-
I
O
N
S

27. (NH4)2(CO3)
Ionic Bonds with Polyatomic Ions
(NH4)+
(CO3)2-
I
O
N
S

28. The subscripts following each element’s symbol represent how many
atoms of that element are present in the molecule formed.
Subscripts (Ionic Bonds with Polyatomic Ions)
In the molecule Ca(OH)2, there is one
Calcium atom and two Hydroxide
molecules.
You can determine the subscripts by
exchanging them with the superscripts of
the ions of the atoms and molecules
involved.
Ions Chemical Formula
Ca2+ (OH)-1 Ca(OH)2

29. When two neutral nonmetals share electrons they form a covalent bond.
**NOT Ions
Covalent Bonds
In covalent bonds, atoms do not lose nor gain electrons; they
share them in order to complete their valence electrons.

30. CH4 HCl
NH3
Methane has four Hydrogen atoms, Hydrochloric acid has one, and Ammonia
has three. Why??
Elements rarely exist on their own; they normally have reacted with another
element, sometimes with an identical atom. Only Noble Gases exist
unbonded to another element. Why??

34. The subscripts following each element’s symbol represent how many
atoms of that element are present in the molecule formed.
Subscripts
In the molecule H2O, there are two
Hydrogen atoms and one Oxygen atom.
You can determine the subscripts by
exchanging them with the superscripts of
the natural ions of the elements involved.
Natural Ions Chemical Formula
H1+ O-2 H2O

36. Glencoe Chemistry: Matter and Change. New York, NY: Glencoe/McGraw-Hill, 2002.
Bibliography