1. Periodic Table: Atoms, Classification & Representation
4-Ch 1

2. Review: The Atom What is an atom? What are the parts of an atom?
Definition: An atom is the smallest particle of matter. It cannot be divided chemically
What are the parts of an atom?
In the nucleus: Protons and Neutrons
Outside of the nucleus: Electron
Protons have a positive charge, neutrons have no charge, and electrons have a negative charge

3. How Small is an Atom?

4. The Rutherford-Bohr Atomic Model
Named after two scientists: Ernest Rutherford and Niels Bohr
Rutherford: Discovered that most of the atom is empty space and contains a very small but dense nucleus
Bohr: Electrons surround the nucleus in orbits (pathways) but can move from one orbit to another
Definition: A representation of the atom as a very small nucleus made up of positively charged protons, surrounded by negatively charged electrons moving in defined orbits

5. Representing Atoms (Rutherford-Bohr)
To keep things simple, protons and neutrons are represented as a “ball” in the center (the nucleus)
Electrons are arranged on orbits (also called shells or valences) around the nucleus
Each orbits has a MAXIMUM number of electrons it can support
The number of protons and electrons are EQUAL and we know this number as the ATOMIC NUMBER

6. How Many Electrons? For the first 20 elements: 1st orbit = 2 electrons
2nd orbit = 8 electrons
3rd orbit = 18 electrons BUT after 8 electrons the 4th begins to fill too…
Examples:
Helium: Atomic Number = 2
Aluminum: Atomic Number = 13
Calcium: Atomic Number = 20

7. Example of an Exam Question
Which of the following best represents the aluminum (Al) atom according to the Rutherford-Bohr model?

8. Representing Atoms (Lewis Notation)
A simplified representation of the atom
Only valence electrons are shown
Valance Electrons: the electrons located FURTHEST from the nucleus

9. The Periodic Classification of the Elements  The Periodic Table
Periodic Classification: A way to group the elements according to certain properties
Periodic Table of Elements: a visual presentation of the elements in groups according to their physical and chemical properties

10. Review: Physical vs Chemical Properties
Physical Property: A property that can be observed or measured without changing the make-up of the matter of the object (ex: colour, odor, texture, density, melting point, boiling point)
Chemical Property: Cannot be determined by simply viewing or touching the object; only becomes evident during a chemical reaction (ex: reactivity with other chemicals, flammability, heat of combustion)

11. Periodic Table Organization Activity
Each team will be given a collection of shapes
Each shape (piece) has two numbers on it
You task is to decide how to best organize ALL of the pieces into one table where each row (goes across) and each column (goes up and down) share similar characteristics (you cannot simply put them in a single line)
When your team is done, you will have a work sheet to complete based on the activity.

12. How the Periodic Table is Divided/Organized
Each element has its own box/square
For each element:
Symbol of the Element: This is universal (same for all languages)
Atomic Number: always located at the top
Atomic Mass: always located at the bottom
Name of the Element: Written in the language of the document

13. First Major Division: Metals, Non-Metals & Metalloids
All the elements can be placed into these three categories
The “staircase” helps locate and identify the categories

14. Metals Location: To the LEFT of the staircase Properties:
Conduct heat and electricity well
Ductile (can stretch)
Malleable (can bend)
Usually shiny
Solid at room temperature EXCEPT for Mercury (liquid)

16. Non-Metals Location: To the RIGHT of the staircase EXCEPT for Hydrogen
Properties:
Poor conductors of heat and electricity
Many are gases at room temperature

18. Metalloids Location: Found along the “staircase” Properties:
Only 7 in total (Boron, Silicon, Germanium, Arsenic, Antimony, Tellerium, Astatine)
Have some properties of metals AND some of non-metals
Some are very good conductors, others are very poor – used as semiconductors in circuits and lasers

20. Groups of the Periodic Table
All the elements found in one COLUMN (going up and down) belong to a GROUP
All elements in a group have:
Similar chemical properties
The same number of valence electrons
Groups are labeled using Roman numerals (1 = I, 2 = II) and either A or B
“A” = main elements (biggest columns)
“B” = transition elements (short columns)
Roman numeral = number of valence electrons

21. Alkali Metals
Location: The first column on the left of the periodic table (except Hydrogen)
Properties:
Soft
HIGHLY reactive metals

22. Alkaline Earth Metals
Location: The second column on the periodic table
Properties:
Highly malleable (soft)
Reactive
Burn easily in the presence of heat

23. Halogens Location: The second-last column on the periodic table
Properties:
Non-metals
React easily to form compound
Commonly form salts

24. Noble Gases (Inert Gases)
Location: The final column of the periodic table (on the right)
Properties:
Very stable, do not react well
Commonly found in nature

25. The Periods of the Periodic Table
Elements found in each row (going across) have the same number of shells around the nucleus
The period number corresponds to the number of electron shells