1. Properties of Atoms and the Periodic Table
Chapter 17
Properties of Atoms and the Periodic Table

2. Section 1 – Structure of the Atom
Look at elements and their symbols

3. What’s in an atom?
Atom: smallest piece of matter that still is the element
Nucleus: positively charged center of atom containing
Protons: particle with 1+ charge
Neutrons: particle with NO charge
Electrons: surround nucleus in cloud and have 1- charge

4. Even smaller… Quarks: make up protons and neutrons NOT electrons
Found using a particle accelerator
Speed up particles and smash them into each other
Found 6 quarks

5. Models Represent things that are hard to visualize
Model of the atom has changed many times
Pg. 510 in book

6. Today’s model of atom
Electron cloud model: nucleus in middle and cloud around nucleus where electrons are most likely found

7. Section 2 – Masses of Atoms
Nucleus has most of mass
Proton: x g
Neutron: x g
Electron: x g
Mass of proton and neutron are about 2,000 times bigger than electron!!

8. Atomic Mass Need better numbers for masses Atomic Mass Unit (amu)
Proton: 1 amu
Neutron: 1 amu
Electron ~ negligible

9. Protons Identify Element
Each element has different # of protons
The number of protons tells you what type of element you have
Atomic Number: the number of protons

10. Mass Number Mass Number: SUM of protons and neutrons
# of neutrons = mass # - atomic #
Carbon – 12 and Carbon – 14
Mass Number

11. Mass Number How many neutrons are in the Carbon-14 atom?
Sodium has a mass number of 23. How many protons and neutrons does it have?
Copper – 63: how many protons and neutrons?

12. Isotopes
Def: atoms of the same element that have different # of neutrons
Isotopes: Boron – 10 and Boron – 11
Average Atomic Mass: weighted-average mass of mixture of isotopes

13. Calculating Average Atomic Mass
Four out of five boron atoms are boron-11 and one out of five are boron-10. What is the AAM?

14. Section 3
The Periodic Table

15. Organizing the Elements
Periodic – repeated in a pattern
Late 1800s – Dimitri Mendeleev – Russian – organized elements by increasing masses
Discovered a pattern with chemical properties, they repeated  Periodic

16. Mendeleev’s Periodic Table

17. Current Periodic Table
1913 – Henry Moseley – English – organized elements by increasing atomic number

18. The Atom and the Periodic Table
Vertical columns = Groups / Families
Use A group numbering
Families have similar properties

19. Location of Electrons In neutral atom, # of protons = # of electrons
Energy levels
close to nucleus = low energy
farther away = higher energy

20. Energy Levels and Electrons
Same group = same # of e- in outer energy level
Energy levels are 1 – 7
Filled outer energy level = 8 e-
Levels 3 and higher have inner sub-levels

21. Energy Levels and Electrons
Horizontal rows = Periods
Increase by 1 p+ and 1 e- as you move right
Each row ends with atom with filled outer energy level

22. Electron Dot Diagrams Group #s = # valence e-s (outer e-s)
Def: uses the element symbol and dots to represent outermost electrons
Atoms bond to get a filled outer energy level
Which groups would likely react?

23. Regions of the Periodic Table
Metals, Non-metals, and Metalloids

24. Metals
Conductors of heat and electricity
Luster/shine
Mostly solid

25. Nonmetals Poor conductors of heat and electricity Many are gases
Solids are brittle

26. Metalloids
Semiconductors of heat and electricity