Ionic and Covalent
bonding
What holds atoms together?
Ionic Bonds
• A bond that holds atoms together by the
attraction between oppositely charged ions
• Ionic bonds are formed by the transfer of
electrons
• Ionic compounds form very strong bonds
• Ionic compound conduct electricity when
dissolved in water
– Because ions are free to move
Ionic bonds/compounds
• Likes repel ----------opposites attract
• Metal elements form cations (+ charge)
• Nonmetals form anions (- charge)
Always write the cation first,
then the anion when writing
chemical formulas
Naming cations
• Cation names always stay the same
– Sodium, Na
• Sodium ion Na+
– Calcium, Ca
• Calcium ion Ca2+
Naming Anions
• Anions always change from their original ending to
an (ide) ending
– Ex
– sulfur, S
• Sulfide S2-
– Fluorine, F
• Fluoride ion F-
– Chlorine, Cl
• Chloride ion Cl-
Try writing the ionic names for
the following elements
• Bromine
• Iodine
• nitrogen
Steps for Naming Compounds
Sodium Chloride
1. List the symbols for each ion with their charge
1. Ex. Na+ Cl-
2. Put the cation first
1. Ex. Na+Cl-
3. If there is a roman numeral it is the + charge on
the cation
4. Make sure that the charges (+ and -) equal an
overall charge of zero
1. Ex. Na+Cl- (+1 plus -1 = 0)
5. If they don’t equal zero you must change
the subscript
6. Find the lowest common multiple of the
charges and divide to find new subscripts
7. Write the chemical formula
Ex. NaCl
Polyatomic Ions
• An ion made of two or more atoms (THEY ARE
COVALENT COMPOUNDS WITH A CHARGE)
• You must treat them like a single unit when writing
chemical formulas
–
–
–
–
Ex
CO32- (Carbonate Ion)
That means that CO3 has a charge of 2If there are more than one polyatomic ion put them in
parentheses (CO3)2
– Don’t write the charges in final answer
• NO2– Nitrite ion
– It has a negative charge
– How would you write it if you had three of them?
• (NO2)3
• Sulfate ion
– SO42– What if you had one of them?
• SO4
Practice
• Rubidium Oxide
– Rb2O
• Calcium Chloride
– CaCl2
• Potassium Sulfate
– K2SO4
• Ca3N2
– Calcium Nitride
• Ca3(PO4)2
– Calcium Phosphate
• SrS
– Strontium Sulfide
• K2CO3
– Potassium Carbonate
How Many Atoms?
•
•
•
•
•
Cu2S
FePO4
Ca3(PO4)2
CoCO3
Be(OH)2
Metallic bonds
• Bond formed between two or more of the
metal elements
• Bond formed by attraction of positive metal
ions and electrons around them from other
metal atoms
• Metals conduct electricity when solid
• Metals share electrons and they can move
from one atom to the next
Covalent Bonding
• Formed by nonmetals
• When atoms share electrons
• Covalent bonds form between two
or more
elements above the step
• When naming covalent compounds don’t worry
about charges at all
• All you have to know is the prefixes which tell us
how many atoms there are
• Video
• Hydrogen
•Chlorine
• They can share more than one pair of
electrons
To name covalent copmounds
• Never put mono on first element (only on
second element if there is one of them)
• Change ending of second element to (ide)
Examples
• BF3
– Boron trifluoride
• N 2O 4
– Dinitrogen tetroxide
• AsCl5
– Arsenic pentachloride
• C3S8
– Tricarbon Octasulfide
Try these problems
• P2O5
• Na2O
• Ni(CN)3
• Disilicon hexabromide
• Potassium nitride
– K3N
Polyatomic ions
• Groups of covalently bonded atoms that
have lost or gained an electron