Download The Atom

The Atom
1- Democritis- Matter can be divided to its smallest part the atom.
Greek atomos- indivisible
Dalton Model- 1800’s an English Chemist
- All elements are composed of atoms
- Atoms of the same element are exactly alike
- atoms of Different Elements are different
- compounds are made by joining elements
Thomson’s Model- atoms have positive and negative particles
Rutherford Model- 1908 an English physicist
-atoms are mostly empty space
- have a small dense positively charged center,
the nucleus
- negative charge particles around the nucleus,
electron
Bohr Model- Bohr Model 1913, Danish Scientist
- electrons move in orbits around the nucleus
( just like a solar system)
- orbits or energy levels are located at certain
levels from the nucleus
Wave Model- electrons do not move in a perfect orbit,
- only a prediction can be made where an electron will be
Modern Atomic Theory- A small positively charged nucleus
- nucleus surrounded by electrons ( an equal but opposite
charge of the proton)
The Atom
Nucleus
- consists of two types of particles ( protons and neutrons)
- 99.9 % of the mass of the atom
- hundred thousand times smaller than the atom
Protons
Neutrons
Electrons
- positively charged particles
- mass of 1 amu ( atomic mass unit)
- electrically neutral
- mass of slightly more than 1 amu
- 1/2000 the mass of a proton
- negatively charged particle
- in an uncharged atom the electrons equals the protons
- circle the nucleus
Atomic Number - the number of protons in the nucleus
- always the same in an element
Mass Number
- the number of protons and neutrons in an atom
- on the periodic table the atomic mass is the average of all
isotopes of an atom found in nature
How many protons and neutrons are in Carbon 12 and Carbon 14?
Isotopes
- elements with the same # of protons but a different
amount of neutrons in the nucleus
The Atom
Isotopes of Hydrogen
Protium Nucleus
Electron cloud
Deuterium Nucleus
Tritium Nucleus
- the space in which an electron is most likely found in an atom
- energy levels
- location in a cloud that an electron is likely to be found
- electrons with a higher level are farther from the nucleus
- electrons with lower energy are closer to the nucleus
First level - 2 electrons
Second Level - 8 electrons
Third Level - 8 elecrons
Properties of element depend on the outer shell
- unfilled shells are unhappy and want to be filled
- 1st energy level can hold 2 electrons
- 2nd energy level can hold 8
Octet Rule - an atom is stable ( un-reactive)
Valence Shell
if it has 8 electrons in its outer shell
- the outermost shell is the valence shell
- the electrons in the valence shell are the valence electrons
The Atom
Quantum Forces
Weak Force
Strong Force
- force that holds protons and neutrons together
- holds the neutrons and protons in the nucleus
Electromagnetic Force- positive and negative forces of electrons and protons
holding the nucleus atom together
Sub Atomic Particles ( Quantum Mechanics )
Quarks - small particles that make up protons and neutrons
Leptons - small particles that make up electrons
Fundamental Forces of Physics