1. Physical Science
Ch. 19

2. Section 1
Stability in Bonding

3. Compounds
Two or more elements combining to make a substance
Compounds have different properties than the elements that make them up

4. Chemical Formula Subscript
composed of symbols and subscripts indicating the number of atoms of an element in a compound.
Subscript
Means “written below”

5. Atoms form compounds when the compound is more stable than the separate atoms.
Noble gases
Elements in far right column
Are more chemically stable than other elements because they have a complete outer energy level.

6. Stable Compounds Chemical bond
Elements that do not have full outer energy levels are more stable in compounds.
Atoms can lose, gain, or share electrons to get a stable outer energy level.
Chemical bond
the force that holds atoms together in a compound.

7. Section 2
Types of Bonds

8. Forming a bond Chemical Bonds
When two elements come together by either transferring or sharing electrons
When elements lose or gain electrons
The result of bonding is a net charge of zero

9. Ion
A charged particle because it has more or fewer electrons than protons.
Cation
Positively charged ion
When an atom loses an electron
Anion
Negatively charged ion
When an atom gains an electron

10. Molecules Covalent bond
Neutral particles formed as a result of sharing electrons.
Covalent bond
the force of attraction between atoms sharing electrons.

11. Ionic bond Chemical Bonding
the force of attraction between opposite charges of the ions
Chemical Bonding
Result is a neutral compound.
Sum of the charges is zero.

12. Atoms can form double or triple bonds depending on whether they share two or three pairs of electrons
Saturated
all single bonds
Unsaturated
Not all single bonds
Must contain at least one double or triple bond

13. Polar molecule Nonpolar molecule Opposite ends have opposite charges
electrons are shared equally.

14. Ionic Compounds Covalent Compounds With ions (cations and anions)
Between metal and non-metal
Transfer of electrons
Covalent Compounds
With molecules
Between two non-metals
Sharing of electrons

15. Writing Formulas and Naming Compounds
Section 3
Writing Formulas and Naming Compounds

16. Chemists use symbols from the periodic table to write formulas for compounds.
Binary compound
composed of two elements
Oxidation number
how many electrons an atom has gained, lost, or shared to become stable
The apparent charge on an element

17. When writing formulas, remember that the compound is neutral.
To write formulas
Use oxidation numbers
Least common multiples
When writing formulas, remember that the compound is neutral.
A formula must have the correct number of positive and negative ions so the charges balance
The formula must have a neutral charge

18. Writing Binary Compounds
Write down first element & it’s oxidation number
Write down second element & it’s oxidation number
Add multiples of the appropriate element until total charge is zero
Use subscripts to show ratio of the atoms of each element

19. Calcium Oxide
Ca +2
O-2
So 1 Ca and 1 O
CaO

20. Lithium Nitride
Li +1
N-3 +1
So 3 Li and 1 N
Li3N

21. Magnesium Phosphide
Mg +2
P-3
+2 -3 +2 -3
So 3 Mg and 2 P
Mg3P2

22. Potassium Sulfide
K +1
S-2
+1 -2 +1
So 2 K and 1 S
K2S

23. Naming Binary Compounds
Write down name of first element
Write down name of second element
Change the ending of the second element to –ide

24. NaCl
Sodium
Chlorine
-ide
Sodium Chloride

25. K2O
Potassium
Oxygen
-ide
Potassium Oxide

26. Poly Polyatomic ion Means “many”
positively or negatively charged, covalently bonded group of atoms
Many atoms

27. Binary covalent compounds
Hydrate
compound with water chemically attached to it
Binary covalent compounds
Name by using prefixes to indicate how many atoms of each element are in the compound

28. Prefixes for Covalent Compounds
Mono-
Di-
Tri-
Tetra-
Penta-
Hexa-
Hepta-
Octa-
Non-
Dec-
Prefixes for Covalent Compounds