1. The Atom

2. anything that has mass and takes up space matter is made up of atoms
What is Matter?

3. How Small are Atoms?
It would take a stack of about 50,000 aluminum atoms to equal the thickness of a sheet of aluminum foil from your kitchen
If you could enlarge a penny until it was as wide as the US, each of its atoms would be only about 3 cm in diameter – about the size of a ping pong ball
A human hair is about 1 million carbon atoms wide
A typical human cell contains roughly 1 trillion atoms
A speck of dust might contain 3x1012 (3 trillion) atoms
It would take you around 500 years to count the number of atoms in a grain of salt

4. Results How many cuts were we able to make?
Do you think we could keep cutting the paper forever? Why or why not?
You would have to cut the paper in half around thirty-one (31) times to get to the size of any atom.

5. What are Subatomic Particles?
the smallest unit into which matter can be divided
building blocks of all matter
comprised of a nucleus (at it’s center) and an electron cloud (surrounding the nucleus)
made up of sub-atomic particles
smaller than an atom
protons
neutrons
electrons
What is an Atom?
What are Subatomic Particles?

6. Early Atom Models: What is the Rutherford Model?
mostly empty space
small, positive nucleus
contained protons and electrons scattered around the outside
Early Atom Models: What is the Rutherford Model?

7. Early Atom Models: What is the Bohr Model?
electrons move in definite orbits around the nucleus

8. Modern Atom Model: What is the The Electron Cloud Model?
sometimes called the wave model
spherical cloud of varying density
varying density shows where an electron is more or less likely to be
Modern Atom Model: What is the The Electron Cloud Model?

9. + What are Protons? positively charged particles (+)
help make up the nucleus of the atom
equal to the atomic number of the atom
contribute to the atomic mass
equal to the number of electrons + - +

10. What are Neutrons? neutral particles; have no electric charge
help make up the nucleus of the atom
contribute to the atomic mass + -

11. - What are Electrons? negatively charged particles (-)
found outside the nucleus of the atom in the electron orbits/levels
each orbit/level can hold a maximum number of electrons
1st orbital = 2 electrons
2nd orbital = 8 electrons
3rd orbital = 8 electrons + - -

12. What are Electrons?
move so rapidly around the nucleus that they create an electron cloud
mass is insignificant when compared to protons and neutrons
equal to the number of protons
involved in the formation of chemical bonds + - -

13. What are Valence Electrons?
found in the outermost energy level of the electron cloud (called the valence shell)
involved in bonding
determine the chemical properties of an element

14. How is the Atom’s Center Formed?
Protons and neutrons are grouped together to form the “center” or nucleus of an atom
Notice that the electrons are not apart of the nucleus - + - - -

15. Atomic Structure

16. How are Atoms Described?
atomic number = number of protons
in a neutral atom, the # of protons = the # of electrons
atomic mass= the number of protons + the number of neutrons

17. What would be the atomic number of this atom?
the number of protons in the nucleus of an atom
What is Atomic Number? - + - -
What would be the atomic number of this atom?

18. + What is the Atomic Mass? +
the total number of protons and neutrons in an atom’s nucleus
expressed in Atomic Mass Units (amu)
each proton or neutron has a mass of 1 amu
What would be the atomic mass of this atom? - +
 3
 4 + -
3 protons + 4 neutrons = an atomic mass of 7 amu
Why did we not account for the electrons when calculating the mass number? -

19. Hydrogen (H) Atom
Let’s use the Bohr Model to sketch a hydrogen atom.
notice the one electron in the first orbital - + -
= 1
= 0 +
P = Atomic # =
E = P =
N = Atomic Mass – Atomic # =

20. Oxygen (O) Atom
notice the two electrons in the first orbital/level and the six in the second
Bohr Diagram
P = Atomic #
________
E = P
N = Atomic Mass – Atomic #

21. Sodium (Na) Atom Bohr Diagram P = E = N =
notice the two electrons in the first orbital/level, eight in the second, and one in the third
Bohr Diagram
P =
E =
N =

22. Building Atoms Atoms Protons Neutrons Electrons Carbon 6 Beryllium 4 5
Using the whiteboard and the proton, neutron, and electron pieces, build the following atoms, and determine their atomic and mass numbers.
Atoms
Protons
Neutrons
Electrons
Carbon 6
Beryllium 4 5
Oxygen 8
Lithium 3
Sodium 11 12