1. ATOMIC STRUCTURE

2. ATOM: smallest piece of an element. Atoms are TOO SMALL TO SEE with our eyes.Atoms are TOO SMALL TO SEE with our eyes. We must USE EVIDENCE from experiments to CREATE MODELS of what atoms might look like.We must USE EVIDENCE from experiments to CREATE MODELS of what atoms might look like.

3. MODEL: a representation of an object or event. Models of the atom started being made approximately 2500 YEARS AGO.Models of the atom started being made approximately 2500 YEARS AGO. These models have been changed due to better observations.These models have been changed due to better observations.

4. DEMOCRITUS’ MODEL: all matter is made of TINY PIECES (atomos) that CANNOT BE DIVIDED. Liquid atoms were round and smooth. Liquid atoms were round and smooth. Solid atoms were rough and prickly. Solid atoms were rough and prickly.

5. ARISTOTLE’S MODEL: all matter is made of FOUR ELEMENTS. HOTDRY WETCOLD FIRE EARTH WATER AIR

6. DALTON’S MODEL: all matter is made of individual particles called ATOMS, which CANNOT BE DIVIDED into smaller pieces.

7. DALTON’S THEORY: All elements are made of atoms.All elements are made of atoms. All atoms of the same element have the same mass (atoms of different elements have different masses).All atoms of the same element have the same mass (atoms of different elements have different masses). Compounds contain atoms of more than one element that always combine the same way.Compounds contain atoms of more than one element that always combine the same way.

8. THOMSON’S MODEL: atoms are made of smaller pieces, called SUBATOMIC PARTICLES.

10. THOMSON’S PLUM PUDDING MODEL CHOCOLATE CHIP ICE CREAM The ice cream is a mass of positively charged matter. The ice cream is a mass of positively charged matter. The chips are negative particles spread throughout the matter (ice cream). The chips are negative particles spread throughout the matter (ice cream).

11. RUTHERFORD’S MODEL: all of an ATOM’S POSITIVE CHARGE is concentrated in the NUCLEUS. Nucleus: dense, positively charged mass located in the center of the atom (nuclei).Nucleus: dense, positively charged mass located in the center of the atom (nuclei).

12. GOLD FOIL EXPERIMENT

13. BOHR’S MODEL: electrons move at CONSTANT SPEEDS in CIRCLES (fixed orbits) around the nucleus, called ENERGY LEVELS.

14. ELECTRON CLOUD MODEL (MODERN THEORY): describes the POSSIBLE LOCATIONS of electrons around the nucleus.

15. THOMSONRUTHERFORDDALTON BOHRELECTRON CLOUD

16. SUBATOMIC PARTICLES Rutherford had found evidence of two subatomic particles. Rutherford had found evidence of two subatomic particles. He predicted a third existed. He predicted a third existed. ELECTRONS, PROTONS, and NEUTRONS are all subatomic particles. ELECTRONS, PROTONS, and NEUTRONS are all subatomic particles.

17. ELECTRONS: e - e - NEGATIVELY charged (-1) NEGATIVELY charged (-1) Found OUTSIDE the NUCLEUS Found OUTSIDE the NUCLEUS The mass of 1,836 electrons equals the mass of 1 proton The mass of 1,836 electrons equals the mass of 1 proton

18. PROTONS: p + p + POSITIVELY charged (+1) POSITIVELY charged (+1) Found INSIDE the NUCLEUS Found INSIDE the NUCLEUS Same mass of 1 neutron Same mass of 1 neutron

19. NEUTRONS: n n NO electric CHARGE (0) NO electric CHARGE (0) Found INSIDE the NUCLEUS Found INSIDE the NUCLEUS Same mass of 1 proton Same mass of 1 proton

21. ATOMIC NUMBER: the number of protons in one atom. Its different for every element.

22. MASS NUMBER: the sum of the protons and neutrons in the nucleus of one atom. (Number of neutrons = mass number – atomic number)

23. ISOTOPE: atoms of the same elements that have DIFFERENT NUMBERS OF NEUTRONS and DIFFERENT MASS NUMBERS. Atoms of the same element can have ONLY DIFFERENT NUMBERS OF NEUTRONS.Atoms of the same element can have ONLY DIFFERENT NUMBERS OF NEUTRONS.