1. Atomic Structure - Two Observable Facts made in the 1800’s
Law of Conservation of Mass
Matter is neither created nor destroyed in a chemical reaction
Law of Constant Composition
The elements present in a compound are present in a fixed and exact proportion by mass

2. Dalton’s Atomic Theory
From 1803 to 1808 an English schoolmaster named John Dalton came up with a very good Atomic Theory.
All matter is composed of atoms (Dalton thought they were indestructible)
Atoms are the building blocks of matter
Atoms of one element are identical

3. Dalton’s Atomic Theory
Atoms of different elements can be distinguished by their different masses
Compounds are combinations of atoms of different elements and possess properties different from those of their component elements
In chemical reactions, atoms are neither created nor destroyed but only exchanged between starting compounds to form new compounds

4. Questions: How is a Hydrogen atom different from a Helium atom?
Is there something that makes them different?
We need to look at their structure to understand the difference

5. The Structure of Atoms Atoms aren’t the smallest particles of matter
They are made up of three types of particles
Proton - a positively charged particle
Neutron - a neutral particle
Electron - a negatively charged particle (much lighter than a Proton or Neutron)

6. A picture of the Atom
The nuclease is at the center of the atom and contains the protons and neutrons - it is very small compared to the atom
A pea at the center of the WSU football stadium is about the same ratio
The electrons occupy the rest of the space of the atom

7. The Charge of the Atom
The charge of a proton is exactly opposite of the charge of an electron
The proton is +1 and the electron is -1
The number of protons in an atom is unique to each element and is called the atomic number
An atom having a net electrical charge is called an ion.
A positively charged atom is a cation
A negatively charged atom is an anion

8. Atomic Mass Each atom has a set mass to it
Because Carbon is so prevalent in life we use it as a standard and assign it a mass of 12.
Everything else is compared to Carbon
Hydrogen is 1.008

9. Isotopes
Atoms of the same element have the same number of protons (atomic number)
The number of neutrons in an atom can vary
a family of elements with atoms having the same chemical properties but slightly different masses.
These atoms with differing masses are called isotopes
An isotope is identified by its mass number: the sum of the number of protons and the number of neutrons it contains

10. Group Work
Write the element (with atomic mass and atomic number) and charge for each
4 protons, 5 neutrons, 2 electrons
26 protons, 29 neutrons, 26 electrons
9 protons, 10 neutrons, 10 electrons
80 protons, 121 neutron, 78 electrons

11. The Periodic Table - History
Two scientists, Dmitri I Mendeleev (Russia) and Lothar Meyer (Germany)
properties of elements did not change smoothly with increasing atomic mas.
Instead the properties of the elements repeated periodically.
Periodic Law: the properties of the elements repeat periodically as the elements are arranged in order of increasing atomic number (# of protons)
This periodic law is used to form the Periodic Table

12. The Periodic Table - Categories
Three Categories: Metals, Non-metals, Metalloids

13. Details of the Periodic Table - Group
The elements in the same vertical column are called a group and have similar chemical properties
Nobel Gasses - Neon Lights, Lasers
Halogens
Chlorine (Cl), Bromine (Br) and Iodine (I)

14. Details of the Periodic Table - More Groups
Potassium (K), in Water (H2O)
• Alkali metals
Alkali earth metals
Main-Group Elements
Transition Metal Elements
Lanthanide and Actinide Elements

15. Details of the Periodic Table - Period
The elements in the same horizontal row are called a period
Hydrogen and Helium are in period 1
Lithium through Neon are in period 2 4