1. Defining the Atom Structure of the Nuclear Atom
Atomic Structure
Defining the Atom
Structure of the Nuclear Atom

2. I CAN identify and describe the particles that form an atom.

3. Defining the Atom EARLY MODELS OF THE ATOM
An ATOM is the SMALLEST PARTICLE of an ELEMENT that RETAINS its identity in a CHEMICAL REACTION.
The Greek philosopher DEMOCRITUS was one of the first people to suggest the existence of the ATOM.
Democritus described atoms as INDIVISIBLE and INDESTRUCTIBLE.

4. Early ideas of the atom DID NOT CATCH ON because the philosophers COULD NOT TEST their ideas.
More than 2000 YEARS passed before the idea of the atom became an accepted reality.
JOHN DALTON, an English teacher/chemist, used EXPERIMENTAL methods to test DEMOCRITUS’
ideas about the atom.

5. Dalton’s Atomic Theory
Dalton formulated FOUR STATEMENTS that formed the basis of the modern idea of the atom:
All ELEMENTS are composed of ATOMS.
ATOMS of the SAME element are IDENTICAL.
ATOMS can COMBINE CHEMCIALLY to form COMPOUNDS.
ATOMS keep their IDENTITY during CHEMICAL REACTIONS.

6. Sizing Up the Atom Atoms are EXTREMELY SMALL!
A COPPER PENNY contains approximately x 1022 atoms of copper.
The population of the Earth is approximately
7.0 x 109 (7 billion) people.
THEREFORE there is about 4,000,000,000, [4 TRILLION] times more ATOMS IN A COPPER PENNY than there are people on the Earth!

7. STRUCTURE OF THE NUCLEAR ATOM
SUBATOMIC PARTICLES
(NOTE- While there are 17 Fundamental Particles identified – 6 Quarks, 6 Leptons, 4 Gauge Bosons and the Higgs Boson - and over 200 combination particles, we will focus on only three basic subatomic particles, since we can explain about 99% of all basic chemistry using these three particles)
Atoms are composed of THREE BASIC PARTICLES known as SUBATOMIC PARTICLES.
ELECTRONS were first discovered in 1897.
Electrons have a NEGATIVE electrical charge.
Electrons have a VERY SMALL MASS. It takes 1837 electrons to weigh as much as ONE PROTON. 
The symbol for an electron is e- [note it’s lower case!]

8. PROTONS were first discovered in 1886.
Protons have a POSITIVE electrical charge.
Protons have a mass about 1837 times larger than ELECTRONS.
The symbol for a proton is P+ [note the P is upper case!]

9. NEUTRONS were discovered in 1932.
Neutrons have NO ELECTRICAL CHARGE (they are NEUTRAL)!
Neutrons have a mass ONLY SLIGHTLY GREATER THAN a proton.
The symbol for neutron is N0 [note it is upper case!]

10. THE NUCLEUS AND ELECTRON CLOUD
PROTONS and NEUTORNS are found in the NUCLEUS of the atom.
The nucleus is the SMALL, DENSE and SOLID central core of the atom.
More than 99.9% of the mass of an atom is located in the NUCLEUS.
The atom’s ELECTRONS are found in an area SURROUNDING THE NUCLEUS known as the ELECTRON CLOUD.
The electron cloud can be compared to BEES SWARMING AROUND A HIVE and it mostly just an area of EMPTY SPACE where as the nucleus is a SOLID structure.

11. ATOMIC NUMBER Protons play an extremely important role in the atom.
The NUMBER OF P+ determines the atom’s elemental identity.
Each different element on the PT has a unique number of P+ in its nucleus.
The NUMBER OF P+ in the atom’s nucleus is known as the ATOMIC NUMBER.
In a NEUTRAL ATOM (one that has not reacted with other atoms) the ATOMIC NUMBER is also equal to the NUMBER OF ELECTRONS the atom has.
ATOMIC NUMBER is abbreviated simply as “AN”.
ANs are WHOLE, SEQUENTIAL numbers found at the top of each element’s box on most periodic tables.

12. ATOMIC MASS NUMBER
Along with the atomic number, the subatomic particles of an atom contribute to other numbers.
One important one is the ATOMIC MASS NUMBER, abbreviated as “AMN”.
As it’s name implies, it represents the MASS OF ONE ATOM. The unit for AMN is a derived unit known as the ATOMIC MASS UNIT, or simply “amu” or more simply “u”.
The AMN is calculated by adding the total number of PROTONS and NEUTRONS in the atom together.
On the Periodic Table, the AMN is generally on the top or bottom of each element’s box (depends on the PT you use) and, with only a few exceptions, is a number WITH A DECIMAL.