1. Chapter 5 – Atoms & Bonding

2. Electron Shells
Electrons aren’t the same distance from the nucleus. They are arranged in shells or energy levels.
The period # tells you the number of energy shells for each element in a period
Each shell can hold only a certain number of electrons.
Electrons are in constant motion and can move between levels. Electrons closest to the nucleus have the least energy and the electrons in the outermost shell have the most energy
The orbitals are not set paths like planets around the sun. They are more like boundaries to predict where you will find electrons most of the time based on energy. This is just a model to help visualize the energy levels.

3. Shells First shell = 2 electrons “the sports car”
Second shell = 8 electrons “the mini van”
Third shell= 8 electrons “another mini van”

4. Lets practice!
According to the periodic table how many energy shells would be in an atom of:
Sodium (Na)
Oxygen (O)
How do you know?

5. Valence Electrons & Bonding
The electrons in the outer shell are called valence electrons
The number of valence e- in an atom of an element determines how the atom can bond with other atoms
The family # tells you
the number of valence
electrons for each element
in the family
(A groups only)

6. Lets practice!
According to the periodic table how many valence electrons do the following atoms have:
Sodium (Na)
Oxygen (O)
How do you know?

7. Valence Electrons & Bonding
Atoms are more stable (less likely to react) when they have 8 valence electrons
Atoms can gain or lose electrons in order to have 8 valence electrons
Chemical Bond – the force of attraction that holds two atoms together
The valence e- are the ones involved in bonding. The further away from the nucleus the less the force of attraction between the positive nucleus and negative e-. This is why the valence e- are easily gained or lost to form new chemical bonds

8. Valence Electrons & Bonding
Electron Dot Diagram – includes the symbol for the element surrounded by dots…the dots show the valence electrons

9. Chapter 5 – Atoms & Bonding
Section 3 - Covalent Bonds
Standards
3.b – Students know that compounds are formed by combining two or more different elements and that compounds have properties that are different from their constituent elements.
7.c – Students know substances can be classified by their properties, including their melting temperature, density, hardness and thermal and electrical conductivity

10. Electron Sharing
Covalent Bond – a chemical bond formed when two atoms share electrons

11. How many Bonds?
Use electron dot diagrams to set up an atom to have 8 valence electrons
Electrons can be shared in order to fulfill the octet rule (8 valence electrons)

12. How many Bonds?
Double Bond – two pairs of electrons being shared between two atoms
Triple Bond – three pairs of electrons being shared between two atoms

13. Chapter 5 – Atoms & Bonding
Section 2 – Ionic Bonds
Standards
3.b – Students know that compounds are formed by combining two or more different elements and that compounds have properties that are different from their constituent elements.
3.c – Students know that atoms and molecules form solids by building up repeating patterns, such as the crystal structure of NaCl or long-chain polymers

14. Ions
Ion – an atom or group of atoms that has become electrically charged
When an atom loses an electron it has a positive charge
When an atom gains an electron it has a negative charge
Element
Ion
Hydrogen  
H +
Potassium  
K +
Sodium  
Na +
Barium  
Ba 2+ 
Calcium  
Ca 2+ 
Magnesium  
Mg 2+
Aluminum  
Al 3+  
Boron
B 3+
Lithium  
Li +  
Element
Ion
Flouride  
F - 
Chloride  
Cl -
Bromide  
Br -  
Iodide  
I -  
Oxide  
O 2-  
Sulfide  
S 2-  
Nitride  
N 3-  
Phosphide  
P 3-  
10 electrons
8 valence e-

15. Ions Ionic Bond – the attraction between two oppositely charged ions
Ionic bonds form as a result of the attraction between positive and negative ions
Ionic Compound – compound that consists of positive and negative ions

16. Chemical Formula & Names
Chemical Formula – combination of symbols that shows the ratio of elements in a compound
Ex. MgCl2 or NaCl or K2S
When ionic compounds form, the ions come together in a way that balances out the charges on the ions
Subscript – tells you the ratio of elements in the compound
Ex. MgCl Magnesium ion and 2 Chlorine ions

17. Naming Ionic Compounds
The name of the positive ion goes first
Then the name of the negative ion
If the negative ion is an element, add the ending –ide
If the negative ion is polyatomic, leave the name the same
Mg2+ + O2-  MgO Magnesium Oxide
Na+ + CO32-  Na2CO3 Sodium Carbonate

18. Properties of Ionic Compounds
The characteristic properties of ionic compounds are:
Crystal Shape – orderly 3-D shape
High Melting Point – ionic bonds are strong
Electrical Conductivity – when dissolved in water, ionic compounds conduct electricity

19. Practice with Ionic Bonds
Examples:
Na Cl  NaCl
Na Cl–  NaCl
Mg Cl  MgCl
Mg Cl–  MgCl2
Ca O  CaO
Ca O2–  CaO
Al O  AlO
Al O2–  Al2O3