1. ATOMS AND THE PERIODIC TABLE
CHAPTER 4
Meet the Elements

2. VOCABULARY --- REVIEW and INTRODUCTION
Atoms – smallest part of an element that still retains all properties of that element.
Atoms can be broken down into subatomic particles.
Atoms can combine to form molecules.
Molecule – the smallest part of a compound that still retains all properties of that compound.
ELEMENTS, ATOMS, MOLECULES, COMPOUNDS

3. Subatomic Particles Nucleus – center of atom
Neutrons – no charge
Protons – positive charge
Energy Levels – located around nucleus
Electrons – negative charge
Electrons move in a cloud around the nucleus

4. Atomic Models Bohr’s Model (1913)
Niels Bohr suggested electrons moved in orbits around the nucleus … similar to planets moving around the sun.
Each electron could only move in specific orbits or paths.

5. Atomic Models 1925 – Electron Cloud Model
Electrons move in a region or general area surrounding the nucleus. (called an electron cloud)
An electrons exact speed, direction or location cannot be determined at any one particular moment.
Electrons are located at various distances around the nucleus
Electrons close to the nucleus have LOW energy
Electrons far away from the nucleus have HIGH energy

6. Electron Cloud Model Electrons exist in energy levels
The number of energy levels that are filled will depend on the number of electrons of that atom.
1st energy level holds 2 electrons
2nd energy level – 8 electrons
3rd energy level – 18 electrons
4th energy level – 32 electrons

7. Electron Cloud Model
Octet Rule – An atom is considered stable (happy) when its outer energy level is full of electrons. (8 outer electrons is considered stable).
Valence Electrons – Electrons found in the outermost shell of an atom
Valence Electrons determine the chemical properties of an atom.
When valence shell is not full…the atom will be more reactive

8. Dot Diagrams (Lewis Structure) and Valence Electrons
Uses the symbol of the element and dots to represent the electron in the outer energy level

9. Periodic Table Element Song

10. Dmitri Mendeleev: Father of the Periodic Table
HOW HIS WORKED…
Put elements in rows by increasing atomic weight.
Put elements in columns by the way they reacted.
SOME PROBLEMS…
He left blank spaces for what he said were undiscovered elements. (Turned out he was right!)
He broke the pattern of increasing atomic weight to keep similar reacting elements together.

11. The Current Periodic Table
Mendeleev wasn’t too far off.
Now the elements are put in rows by increasing ATOMIC NUMBER!!

12. Periodic Table
The arrangement of elements according to repeating changes in properties
Each box on the periodic chart contain the atomic number, chemical symbol, name, and average atomic mass.

13. Periodic Table Organization
Groups – A vertical Column of elements
Elements in the same group have the same number of valence electrons.
Elements of the same group have similar chemical properties.
Periods – Horizontal Rows
The number of protons increase by one from left to right (so do # of electrons)

14. Periodic Table Organization
Chemical Symbol – Abbreviated way to write the name of the element (EX: O – Oxygen)
Atomic Number – The number of protons in the nucleus
Atomic Mass Number – The number of protons plus neutrons in the nucleus (often a decimal number)
This number may be rounded…round up if it is .5 or above and down if .4 or below)
The mass number is an AVERAGE

15. Ions and Isotopes
Ions – An atom or group of atoms that has lost or gained one or more electrons and has a negative or positive charge
Occurs when an atom gives up an electron or takes an electron because outer energy levels are not full
CATION – positive ion (loses electrons and becomes positive)
ANION – negative ion (gains electrons and becomes negative)
(pictures)

16. Ions and Isotopes
Isotopes – An atom that has the same number of protons as other atoms of the same element do but has a different number of neutrons.
Isotopes are often radioactive
Used for cancer treatments, preserving foods, etc.
Example: Hydrogen has three isotopes
Protium, Deuterium, Tritium

17. Isotopes of Hydrogen and Carbon

18. Families of Elements
Members of a family in the periodic table have many chemical and physical properties in common…they have similar valence electrons.
3 Groups:
Metals, Nonmetals, Semiconductors
The Periodic Table of Videos - University of Nottingham

19. Hydrogen Hydrogen belongs to a family of its own.
Hydrogen is a diatomic, reactive gas.
Hydrogen was involved in the explosion of the Hindenberg.
Hydrogen is promising as an alternative fuel source for automobiles

20. Metals Four different kinds of metals
Share common properties of: existing as solids at room temperature, shiny, good conductors of heat and electricity

21. 1. Alkali Metals Group 1 Very Reactive…Have only 1 valence electron
Always combined with something else in nature.
Example: Sodium must be stored in oil so as not to react with moisture in air.

22. 2. Alkaline-Earth Metals
Located in Group 2
Have 2 valence electrons
Less reactive than Alkali Metals
Always combined with nonmetals in nature
Ex: Calcium and Magnesium

23. 3. Transitional Metals Groups 3-12 Much less reactive
                                                                             
Groups 3-12
Much less reactive
These elements properties gradually change from being more similar to Group 2 to being more similar to Group 13 as you move from left to right
Examples: Gold, Platinum, Silver

24. 4. Synthetic Elements All elements above #92 are man-made
Many are radioactive

25. Nonmetals Located on the right side of the periodic table
Includes some elements in Groups and all elements in Groups 17-18
Plentiful on Earth
3 Groups

26. 1. Halogens Group 17 Very Reactive
Always combined with another element in nature
Has 7 valence electrons
Used as disinfectants and to strengthen teeth

27. 2. Noble Gases
Group 18
Unreactive; Do not make compounds with anything.
8 Valence Electrons (full outer energy level)

28. 3. Semiconductors (Metalloids)
Intermediate conductors of heat and electricity
Includes 6 elements
Located on the “stairstep line”
Includes: Boron, Silicon, Germanium, Arsenic, Antimony, Tellurium

29. Diatomic Molecules
If these elements are found alone in nature they are always bonded to themselves because they are very reactive.
Example: O2, H2, Fl2, Br2, I2, N2, Cl2
There are 7
Including: Hydrogen, Oxygen, Fluorine, Bromine, Iodine, Nitrogen, Chlorine