1. Chapter 19
Chemical Bonds
Lesson 1

2. Chemical Bond
Strong attractive force between atoms or ions in a molecule or compound.
Formed by:
transferring e- (losing or gaining)
sharing e-

3. Properties Compounds formed Sodium chloride
Properties aren’t anything like those of the individual elements.
Sodium chloride
a compound made from the elements sodium and chlorine.

4. Chemical Formulas chemical formula H2O
elements that make up a compound and the exact number of atoms of each element in a unit of the compound
H2O
contains the symbols H for the element hydrogen and O for the element oxygen.

5. Formulas Subscript means “written below”
tells how many atoms of that element are in a unit of the compound.
no subscript the unit contains only one atom of that element

6. Atomic Stability electric forces noble gases
oppositely charged electrons and protons hold atoms and molecules together
the forces that cause compounds to form.
noble gases
unusually stable.
Compounds rarely form
they are almost always less stable than the original atoms.

7. Ne Stability Octet Rule
most atoms form bonds in order to have 8 valence e- (This is important)
full outer energy level
like the Noble Gases!
Stability is the driving force behind bond formation! Ne

8. The Unique Noble Gases Electron dot diagrams
show only the electrons in the outer energy level of an atom.
Notice that eight dots surround Kr, Ne, Xe, Ar, and Rn, and two dots surround He

9. Energy Levels and Other Elements
Hydrogen
contains one electron in its lone energy level.
has a single dot next to its symbol.
outer energy level is not full.
It is more stable when it is
part of a compound.

10. Energy Levels and Other Elements
Helium
outer energy level contains two electrons.
already has a full outer energy level by itself and is chemically stable.
rarely forms compounds but, by itself, the element is a commonly used gas.

11. Energy Levels and Other Elements
Groups 13 through 17,
Each falls short of having a stable energy level.

12. Energy Levels and Other Elements
Each group contains too few electrons for a stable level of eight electrons.

13. Outer Levels —Getting Their Fill
How does hydrogen, or any other element, trying to become stable, gain or lose its outer electrons?
combining with other atoms that also have partially complete outer energy levels.
As a result, each achieves stability.

14. Stability
Transferring e-
Sharing e-

15. Outer Levels —Getting Their Fill
electron dot diagram
chlorine now has a stable outer energy level.
Sodium had only one electron in its outer energy level
lost to combine with chlorine in sodium chloride.

16. Stability Is Reached
Look back to the next, outermost energy level of sodium.

17. Stability Is Reached atoms chemical bond gain, lose, or share electron
an attraction forms between the atoms, pulling them together to form a compound.
chemical bond
is the force that holds atoms together in a compound.

18. Lesson Check
How many hydrogen atoms are present in one molecule of ammonium acetate,
NH C H O 7
An ion is a positively or negatively charged atom; an ionic bond occurs when oppositely charged ions attract each other and an equal exchange of electrons takes place. 4 2 3