1. Chemical Bonds

2. Atom – the smallest unit of matter “indivisible”
Helium
atom

3. “Cat-Eye-On” “An-Eye-On” NEGATIVE POSITIVE ION CATION ANION
An atom that gains one or more electrons will have a ____________________ charge.
An atom that loses one or more electrons will have a ____________________ charge.
An atom that gains or loses one or more electrons is called an ____________.
A positive ion is called a ______________ and a negative ion is called an _______________.
NEGATIVE
POSITIVE
ION
CATION
ANION
“An-Eye-On”
“Cat-Eye-On”

4. electron shells Atomic number = number of Electrons
Electrons vary in the amount of energy they possess, and they occur at certain energy levels or electron shells.
Electron shells determine how an atom behaves when it encounters other atoms

5. Electrons are placed in shells according to rules:
The 1st shell can hold up to two electrons, and each shell thereafter can hold up to 8 electrons.

6. Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 electrons
C would like to
N would like to
O would like to
Gain 4 electrons
Gain 3 electrons
Gain 2 electrons

7. Chemical bonds: an attempt to fill electron shells
Ionic bonds
Covalent bonds

8. IONIC BOND bond formed between two ions by the transfer of electrons

10. Ionic Bonds: One Big Greedy Thief Dog!

11. 1). Ionic bond – electron from Na is transferred to Cl, this causes a charge imbalance in each atom. The Na becomes (Na+) and the Cl becomes (Cl-), charged particles or ions.

12. COVALENT BOND bond formed by the sharing of electrons

13. Covalent Bonds

14. 2. Covalent bonds- Two atoms share one or more pairs of outer-shell electrons.
Oxygen Atom
Oxygen Atom
Oxygen Molecule (O2)

16. Bohr Model Electron Shells hold a certain number of electrons.
The first shell can hold 2 electrons
The second shell can hold 8 electrons
The third shell can hold 8 electrons
The fourth shell can hold 8 electrons
The Bohr Model shows the atom and how many electrons in each level.

17. Bonds Atoms have electrons arranged in energy levels or energy shells
Electrons in the last (outermost) shell are called valence electrons
Valence electrons let atoms bond with other atoms
Ionic bonding
Gaining or losing electrons
Covalent bonding
Sharing electrons

18. Ionic Bonds and Ions What is an Ion?
A charged atom or molecule that has gained or lost an electron
Remember, in an ionic bond electrons are lost or gained.
Cation : the element that loses an electron
Have a positive charge
Example: H+1 , Na+ , Ca+2
Anion : the element that gains an electron
Have a negative charge
Example: S-2 (Sulfide), Cl- (Chloride),
OH- (Hydroxide)

19. Making Compounds from Ions
To make a compound from ions, you just switch the superscripts and make them subscripts.
Example:
Na+ and Cl- would be NaCl and would be called Sodium Chloride.
Say the first element normally and add –ide to the end of the second element.
Ca+2 and Cl- would be CaCl2 and would be named Calcium Chloride.
K+ and S-2 would be K2S and would be named Potassium Sulfide.
Mg+2 and Cl- would be what?

20. Bonds Molecules can bond and “unbond”
Atoms can re-arranged in different combinations
For example:
CaCO3 (1 atom Ca, 1 atom C, 3 atoms O)
Add heat to re-arranged the atoms:
CaO
CO2

21. Chemical Equations Chemical reactions can be represented by equations
CaCO3  CaO + CO2
Reactants Products

22. Atoms are re-arranged, NOT created or destroyed
Law of Conservation of Matter
Law of Conservation of Mass

23. Chemical Changes Matter is conserved  type of atoms does not change
Nothing is created or destroyed
Mass is conserved  amount of atoms cannot change

24. Chemical Changes To show conservation of mass  Balance equations
Make sure there are the same number of each type of atom in the products and in the reactants

25. The equation for the burning of methane gas in oxygen is:
Balancing Equations
The equation for the burning of methane gas in oxygen is:
CH4 + 2 O2 → CO2 + 2 H2O
Subscript
Shows # of atoms
Coefficient
Shows # of molecules

26. Balancing Equations 1 C  1 C 4 H  4 H 4 O  4 O
No subscript or coefficient is understood to be 1
CH4 + 2 O2 → CO2 + 2 H2O =
C1H4 + 2 O2 → C1O2 + 2 H2O1
1 C  C
4 H  H
4 O  O

27. Practice Balancing 1st Step Mg + 02 MgO Mg- Mg- O- O- 2nd Step
How many atoms on each side?
Mg MgO
Mg- Mg-
O- O-
2nd Step
Make same atoms on each side equal by adding a coefficient.

28. Types of Chemical Reactions
Synthesis Reaction 2 or more simple substances combine to form a more complex substance.
A+B  AB
Decomposition Reaction
A more complex substance breaks down into its more simple parts
AB  A + B

29. Types of Chemical Reactions
Replacement Reactions
Single Replacement
One element replaces another element in the compound.
AB + C  AC + B
Double Replacement
Different atoms in two different compounds trade places.
AB + CD  AC + BD