1. Atoms and The Periodic Table
Chapter 3
Atoms and The Periodic Table

2. Atom Review (Dalton’s Atomic Theory)
Atom: the smallest particle that still has the properties of an element
Elements are made of atoms and atoms of the same element are alike
Atoms combine in order to make molecules (either elements or compounds)

3. Structure of the Atom Inside the nucleus Outside the Nucleus
Protons (positive charge)
Neutrons (no charge)
Outside the Nucleus
Electrons (negative charge)
Electrons are orbiting the nucleus so fast that we can’t determine their exact position
Neutral atoms have no overall charge
They have equal numbers of protons and electrons

4. Calculating Protons, Neutrons, and Electrons
# of protons: Always the same as the atomic # on the periodic table
#of electrons: usually the same as the atomic number. (different in atoms that have a charge)
# of neutrons: Atomic mass – atomic #
Ex. Chlorine has 18 neutrons

5. Drawing Electrons in their orbitals (shells)
The first orbital can hold 2 e-
The second orbital can hold 8 e-
The third energy level can hold 8 e-
Valence Electrons: the electrons in an atom’s outermost shell
Example:

6. Changing Atoms Ions- Atoms that carry a charge Two types of Ions
Atoms gain/lose electrons from their valence shell in order to be more stable.
This causes the # of protons to no longer equal the # of electrons.
Two types of Ions
Anions- Negatively charged atom (gained e- , Has more e- than p+)
Cations- positively charged atom (lost e-, has less e- than p+)

7. Changing atoms (cont.)
Isotopes- Atoms that have the same number of protons, but different numbers of neutrons
Changes the atomic mass of the atom
The atomic mass written on the periodic table is the weighted average atomic mass of ALL the isotopes.
Changing the # of protons = New Element

8. Developed by a Russian chemist named Dmitri Mendeleev (duh-MEE-tree mehn-duh-LAY-uhf)
Mendeleev used the following categories to organize his table:
chemical properties
physical properties
atomic mass
density
color
melting point
Valence electrons

9. Design of the Periodic Table
organizes information in a logical, usable, and meaningful way
allows prediction of physical and chemical properties of an element by position
can predict how elements will react with other elements
arranged in columns and rows because of similar characteristics

10. Columns in the Periodic Table
vertical classification or groupings
often referred to as families or groups
elements within the same family have similar properties

11. Rows in the Periodic Table
horizontal classification or groupings
each row is called a period
elements in a period are not alike in properties, properties change greatly across a given row
the first element in a period is a very reactive metal
the last element in most periods is a noble gas
only seven periods

12. Physical and Chemical Properties of Metals
Physical Properties
luster (shininess)
conductivity of heat and electricity
high density
high melting point
ductility (they are ductile)
malleability (they are malleable)
Chemical Properties
Tend to lose their electrons in a reaction
Metals will have either 1, 2, 3, or 4 electrons in their outermost energy level (depending on the family)

13. Alkali Metals
Group 1
Very reactive because they only have one valence electron
Forms a 1+ ion (ex. Na+)
Found in nature as a compound
YouTube - Alkali Metals: Explosive reactions

14. Alkaline Earth Metals Group 2 2 valence electrons
Form 2+ Ions (ex. Ca2+)
Reactive, but less reactive than alkali metals

15. Transition Metals Groups 3-12 Typically have 3 valence electrons
Less reactive than first 2 families
Most metals we think of are from this family
Very good conductors of heat and electricity

16. Nonmetals (right side of PT)
Physical Properties
No luster
Don’t conduct heat or electricity well
Not malleable or ductile
Can be solids, liquids, or gases
Chemical Properties
Typically gain electrons to fill valence shell
Form Negative Ions (ex. O2-)
React mainly with metals

17. Halogens Group 17 Have 7 valence electrons
Very reactive nonmetals because they need one electron for full valence shell
Are found as solids, liquids and gases at room temp

18. Noble Gases Group 18 Have 8 valence electrons (He only has 2)
Full valence shell makes them unreactive
Also called “inert”

19. Metalloids (Semi-conductors)
Only 7 elements (B, Si, Ge, As, Sb, Te, Po)
Classified as nonmetals but have some properties of metals
Can conduct heat and electricity but not as well as metals.