1. 4.1 Atomic Theory & Bonding
ATOM: smallest particle of an element, has a neutral charge.
PEN = proton(s) + electron(s) + neutron(s)
ELEMENT: made up of 1 type of atom (eg.oxygen O)
IONS: atoms with charges (eg. oxygen is O2-)
MOLECULES: groups of covalently bonded atoms (eg. oxygen molecules are O2)
COMPOUNDS: are made up of at least 2 atoms bonded together.
Hydrogen and oxygen are atoms/elements
H2O is a compound

2. area surrounding the nucleus
Structure of an Atom:
Name
Symbol
Charge
Location
Atomic Mass
Proton p 1+
nucleus
1 AMU
Neutron n
Electron e 1–
area surrounding the nucleus
1/1836 (0)

3. Numbers to Remember : Protons = Atomic Number
Neutrons = Mass number – Atomic number (Mass # - proton #).
Neutrons + Protons = Mass #
Electrons in an atom = atomic number (also proton #)
Electrons in an ion = atomic number – ion charge

4. Families of the Periodic Table:
Columns of elements are called groups, or families
All elements in a family have…
similar properties
bond with other elements in similar ways
have the same number of valence electrons
Family names (on the periodic table!):
Group 1 = alkali metals (1+, highly reactive)
Group 2 = alkaline earth metals (2+, reactive)
Group 17 = the halogens (1-, very reactive)
Group 18 = noble gases (0, unreactive)
Periods are horizontal rows on the periodic table.

5. Where are the following?
INCREASING REACTIVITY
Where are the following?
Atomic Number
Period
Group/Family
Metals
Non-metals
Transition metals
Metalloids
Alkali metals
Alkaline earth metals
Halogens
Noble gases

6. Periodic Table & Ion Formation:
Ions: Atoms that gain and lose electrons to become stable (full valence shells).
1. Cations: metals that lose electrons & form positive ions (Na+)
Multivalent: Some metals can have more than one charge (Fe2+ or Fe3+).
2. Anions: Non-metals gain electrons & form negative ions (O-2)

7. Bohr Diagrams:
Bohr diagrams show how many electrons appear in each electron shell around an atom. (2, 8, 8, 18, 18)
Valence electrons: electrons in the outermost shell ONLY.
If the valence shell is full = stable
If the valence shell is not full = reactive

8. Bohr Diagrams What element is this?
It has = 18 electrons, and therefore 18 protons
It has 8 electrons in the outer (valence) shell
18 p
22 n
Argon!

9. Electrons are transferred from the cations to the anion
Ionic Bonds:
Formed between Metals (cations) & non-metals (anions).
Valence electrons are transferred from metal to nonmetal.
Eg. Li2O
Lithium
Oxygen +
Electrons are transferred from the cations to the anion
Li+ O2- Li+
Lithium oxide,
Li2O
Covalent Bonds:
Formed between two or more non-metals
Valence electrons are shared between atoms
Eg. HF
Hydrogen
Fluorine +
Electrons are shared
Hydrogen fluoride

10. Lewis Diagrams: Only valence electrons are shown
Dots representing valence electrons are placed around the element symbols (on 4 sides, imagine a box around the symbol)
Electron dots are placed singularly,
then they are paired.
Ex: Nitrogen atom

11. Lewis Diagrams for Ions:
Ex. Nitrogen ion
Remove or add electron dots to
make full valence shells.
Square brackets and the charge
are placed around each ion 2+ – –
• •
• •
• •
• •
• •
• •
• •
• •
• •
• •
• •
• •
• •
• •
• •
• •
• •
• • Be Cl Cl Be Cl Cl Be Cl
Since Be2+ wants to donate 2 electrons and each Cl– wants to accept only one, two Cl– ions are necessary
Each beryllium has two electrons to transfer away, and each chlorine wants one more electron
The ionic compound Beryllium chloride is formed

12. Lewis Diagrams For Covalent Bonds:
valence electrons are drawn to show sharing of electrons.
Remember: All atoms “like” to have a full valence shell
The shared pairs (“bonding pairs”) of electrons are usually drawn as a straight line
“lone pairs” are the electrons not shared