1. Using the Periodic Table
Atomic number- always a whole number, increases in order, represents the number of protons in each atom
Atomic name, often in Latin, sometimes uses a common name, sometimes there are disagreements
Atomic symbol – often, but not always, matches the name; Always capitalize the first (only the first ) letter
Atomic mass- the mass of the atoms based on the average of all the most common isotopes 6
Carbon C
amu

2. Chapter 6
Atoms

3. Aristotle, the famous Greek philosopher and scientist, argued that a substance could be divided again and again, forever getting smaller and smaller pieces
During his time people believed the universe was made of four elements; fire, water, earth and air.

4. The idea of “uncuttable” particles was first suggested by Democritus around 440 B.C.
“Atomos” means indivisible

5. Section 1 Atomic Theory
Atomic Theory (by John Dalton) published in 1803
All substances are made from atoms. Atoms cannot be created, divided or destroyed.
Atoms of the same element are exactly alike.
Atoms can join together to form new substances.

6. JJ Thomson discovered the negatively charged electrons inside the atom.
Ernest Rutherford discovered that the atom is mostly empty space with a tiny positive nucleus and orbiting electrons.
Neils Bohr determined that electrons traveled along paths or energy levels.
Schrodinger & Heisenberg

7. Pictures of Atoms

8. Atomic Size Atoms are extremely small…
Aluminum foil is 100,000 atoms thick.
A Penny has 20,000,000,000,000,000,000,000 atoms!

9. What’s Inside an Atom? Protons (+): Neutrons (0): Electrons (-):
Positively Charged Particles
Mass=1amu
Location: Nucleus
Neutrons (0):
Particles with No Charge
Mass=1amu
Location: Nucleus
Electrons (-):
Negatively Charged Particles
Mass= almost zero
Location: Electron Clouds

10. Outside the nucleus, orbiting at nearly the speed of light
Parts of the Atom
Particle
Charge
Location
Size
Proton
Positive
In the nucleus
1 a.m.u.
Neutron
No charge (neutral)
Almost 1 a.m.u.
Electron
Negative
Outside the nucleus, orbiting at nearly the speed of light
Very tiny, 1/1000th a.m.u.

11. Structure of the Atom + Protons Positively charged
Found in the nucleus of the atom (center)
Mass of 1 amu (atomic mass unit)
Gives the element its atomic number on the periodic table
#1 (hydrogen) has 1 proton
#4 (beryllium) has 4 protons
Protrons were discovered by Ernest Rutherford in 1911 and he discovered the empty space within an atom in 1909

12. N Neutrons Neutral charge ( no charge) Found in the nucleus (center)
Mass slightly smaller than a proton, still considered 1 amu
Protons + atomic mass (rounded to the nearest whole number) N

13. Isotope Atoms can often be found with different numbers of neutrons
Hydrogen (H-1), most common 99.9%
Isotope
Atoms can often be found with different numbers of neutrons
Some atoms have only one stable isotope, others have several
Averaging the masses of the isotopes in their correct percentages gives the exact atomic mass for each element
Unstable isotopes break down (radioactive decay)
deuterium (H-2),
tritium (H-3), least common, radioactive

14. Electrons Negatively charged particles
Found outside the nucleus, moving at nearly the speed of light, in specific levels
Most commonly atoms are neutral particles having equal numbers of protons and electrons
Very small ( about 1/1000th of a proton)
Proton
Neutron
Electrons were discovered by J.J. Thompson in 1897

15. * In 1913 Niels Bohr suggested that electrons travel in specific paths called Electron Shells32 18
Each level can only contain a certain number of electrons before it is full
Each level will fill completely before electrons go to the next level
Lower levels fill first 18 8 8 2