1. Atomic Theory and the Modern Atom

2. Atomic Theory
Each of these scientists helped advance and explore the atom
Dalton
JJ Thomson
Millikan
Rutherford
Bohr

3. Dalton Proposed 5 main points of his Atomic theory to
All matter is composed of tiny particles called atoms
Atoms of a given element are identical in size, mass, and other properties
Atoms cannot be subdivided, created or destroyed
Atoms of different elements combine in whole numbers
In chemical reactions, atoms are combined, separated or rearranged.

4. Dalton’s Laws
The Law of Constant Composition: “Any given compound always consists of the same atoms and the same ratio of atoms. For example, water always consists of oxygen and hydrogen atoms, and it is always 89 percent oxygen by mass and 11 percent hydrogen by mass”
The Law of Conservation of Mass: “The total mass of materials before and after a chemical reaction must be the same. For example, if we combine 89 grams of oxygen with 11 grams of hydrogen under the appropriate conditions, 100 grams of water will be produced—no more and no less.”

5. Dalton’s Laws
The Law of Multiple Proportions: “If two elements combine to form more than one compound, the masses of one of the elements that can combine with a given mass of the other element are related by factors of small whole numbers”
For example, water has an oxygen-to-hydrogen mass ratio of 7.9:1. Hydrogen peroxide, another compound consisting of oxygen and hydrogen, has an oxygen-to-hydrogen mass ratio of 15.8:1. The ratio of these two ratios gives a small whole number.

6. Dalton’s Model
Billiard Ball Model

7. JJ Thomson
JJ Thomson used a cathode ray tube to discover electrons have a negative charge
He found that atoms can be broken into electrons in a positive matrix

8. JJ Thomson’s Model
His model is known as the plum pudding model

9. Millikan
Millikan explored the mass of the electron and confirmed that the electron carries a negative charge by his Oil Drop Experiment

10. Rutherford Created a more detailed atomic structure
Bombarded thin gold fold with alpha particles expecting to have the particles to pass though but what he found was that several particles bounced back towards the source

11. Rutherford’s Model Thus discovering the nucleus
Atoms are mostly empty space with negative electrons orbiting a positive nucleus

12. Bohr
Bohr introduced the idea that electrons move in orbits or “shells” around the nucleus.

13. Electron Cloud Model Model used today
Electrons do not travel in orbits, but rather in an electron cloud.

14. Chemical Symbols
There are about a dozen common elements that have a single capitalized letter for their symbol
The rest, that have permanent names have two letters.
The first is capitalized and the second is lower case.
Some elements have symbols from their Latin names.
Ten of the elements have symbols from their Latin or German names.

15. Subatomic Particles All atoms are composed of the same basic particles
Protons
Neutrons
Electrons
The protons and neutrons are located in the nucleus
Electrons are located in a cloud around the nucleus

16. Subatomic Particles
The ATOMIC NUMBER of an element is the number of protons in the nucleus and is always whole number
The MASS NUMBER is the total number of protons and neutrons in the nucleus and is always whole number
The ATOMIC MASS is an average of all naturally occurring isotopes and is usually not a whole number

17. Two different notations
A-Z notation or isotopic notation
Hyphen notation
Name/Symbol-mass
Chromium Ca2+- 40
Atomic Mass
Charge IF PRESENT
Symbol
Atomic Number

18. Subatomic Particles
If atoms have the same number of electrons as protons, the charges overall charge of the atom is neutral
For ions, the electrons can be different.
For positive ions- there is a loss of electrons
For negative ions- there is a gain of electrons

19. Subatomic Particles
Isotopes are atoms of the same element that have different masses.
Isotopes differ in the amount of neutrons

20. Practice
Find the number of protons, electrons and neutrons for the following?
17 electrons 17 protons (35-17=18) 18 neutrons
10 electrons
12 protons
(24-12=12) 12 neutrons
29 electrons
29 protons
(64-29=35) 35 neutrons

21. Practice
Find the number of protons, electrons and neutrons for the following?
17 electrons 17 protons (35-17=18) 18 neutrons
6 electrons
6 protons
(14-6=8) 8 neutrons
47 electrons
47 protons
(108-47=61) 61 neutrons

22. Practice Write the A/Z and Hyphen Notation?
18 electrons 19 protons 21 neutrons
18 electrons
16 protons
18 neutrons