1. Atoms and Elements
Ch. 12

2. What is matter composed of?
The Atom
Smallest unit of an element that can still be identified as that element.
A single atom is made up of smaller particles called subatomic particles.

3. What are atoms made of? Subatomic particles:
Proton = positive electric charge
Neutron = same mass as the proton but has no electric charge
Electron = negative electric charge and is much smaller than a proton

4. Where are the subatomic particles found?
Inside the nucleus
Outside the nucleus
Protons
Neutrons
Electrons
Nucleus = the center of every atom

5. What makes elements different?
All elements contain atoms and all atoms have the same subatomic particles
What makes one element different from another?

6. Atomic Number The number of protons in an atom Identify the element
Aluminum has 13 protons
Gold has 79 protons
Neon has 10 protons

7. Atoms are electrically neutral
Each atom of a given element contains the same number of protons and electrons
Aluminum = 13 protons + 13 electrons
= ???

8. Models of the Atom A long, long, long time ago…
More than 2400 years ago Democritus, a Greek philosopher was the first person to suggest that everything was made of atoms

9. Democritus was not a popular guy…

10. 1897: J.J. Thomson
While investigating electricity, he discovered the electron
He said it is really small and is negatively charged
But everyone knew that objects
didn’t have a charge….

11. Plum Pudding Model
Plum Pudding Model = electrons are like raisins in plum pudding and the pudding cancels out the negative charge of the electrons

12. 1911: Ernest Rutherford Gold Foil Experiment
He found that Thomson was incorrect!
Atoms are mostly empty space.

13. Gold Foil Experiment

14. 1913: Niels Bohr Suggested electrons orbit the nucleus
Today we know electrons don’t orbit…instead they are found in certain areas called electron clouds

15. Bohr’s Model of the Atom

16. Today’s Model of the Atom

17. Isotopes Not all atoms of the same element have the same mass
What could change the mass of an atom but not change it’s identity?
Isotope = atoms with the same number of protons but different numbers of neutrons

18. Elements Element = a substance that contains only one kind of atom
Elements cannot be broken down into simpler substances
Atomic number = the number of protons in an atom

19. Classifying Elements Metals Usually solids Conduct heat
Conduct electricity
Malleable = can be pounded into thin sheets
Usually shiny

20. Classifying Elements Nonmetals Do not conduct heat
Do not conduct electricity
Dull
Usually gases

21. Periodic Table Developed in 1869
A table that organizes the elements according to their atomic number
Elements Song

22. Periodic Table

23. Periodic Table
Each box on the periodic table contains information about each element:
Name
Atomic number
Atomic mass
Symbol

24. Periodic Table
Name =
Atomic Number =
Atomic mass =
Symbol =

25. Periodic Table
Name =
Atomic Number =
Atomic mass =
Symbol =

26. Periodic Table
Name =
Atomic Number =
Atomic mass =
Symbol =

27. Periodic Table
Metals
Nonmetals

28. Compounds
Compound = a substance made of atoms of 2 or more elements that are chemically combined.

29. Table salt…a compound + =

30. Compounds Atoms in a compound stay together because they form bonds.
Some atoms bond by sharing electrons.
Some atoms bond by transferring electrons.

31. States of Matter Solids Definite shape Definite volume
Atoms are tightly packed close together

32. States of Matter Liquids Definite volume No definite shape
Takes the shape of its container
Atoms are farther apart than they are in solids

33. States of Matter Gases No definite volume No definite shape
Fills the entire volume of its container
Atoms are the farthest apart

34. States of Matter Energy Solids = atoms have the least amount of energy
Gases = atoms have the most amount of energy

35. Solids, liquids and gases

36. Changes of State Melting point
The temperature at which a substance changes from a solid to a liquid

37. Changes of State Boiling point
The temperature at which a substance changes from a liquid to a gas
Also called evaporation

38. Changes of State Sublimation
The temperature at which a solid changes directly to a gas

39. What causes a substance to change its state of matter?
Adding or removing heat
Heat is energy
Adding or removing pressure

40. States of Matter Plasma
A substance made of charged atoms, uncharged atoms, and electrons
Happens when gases get very hot
Rare on Earth
Makes up 99% of the universe

41. Uses of Plasma Fluorescent bulbs Neon signs Computer chips
Welding steel