1. The Atomic Nature of Matter
Chapter 11
The Atomic Nature of Matter

2. Atoms
Building blocks of matter
Everything is composed of atoms

3. Elements atoms of the same kind there are 115 known elements to date
Every element is unique, and has its own set of properties
All atoms of the same element have the same # of protons.

4. Atoms are recyclable
the same atoms have been here since the beginning of time
Combine w/ other elements, then go back to original form and back again
You may be breathing the same air as Julius Caesar or George Washington….

5. Atoms are very small Cannot view individual atoms w/ visible light
Only way to “see” atoms is w/ Scanning Tunneling Microscope
About 1023 (or ) atoms in one thimble-full of water

6. Brownian Motion Jiggling of atoms Atoms are constantly moving
Molecular motion never stops unless a substance is at a temperature of (-273˚ C) a.k.a. absolute zero

7. Molecules combinations of atoms ex. H2, H2O, NaCl, N2
Can be combinations of the same atom, or of different types of atoms

8. Compounds
combinations of atoms of different elements ex. NaCl, H2O, HCl
A compound is always a molecule, but a molecule may not necessarily be a compound (examples …. H2 , N2 )

10. Rutherford Experiment
Gold Foil - showed atoms are largely empty space, very dense nucleus that reflected charged particles backwards
Like a “shooting a 15-inch artillery shell at a piece of tissue paper and having it come back and hit you”

11. Nucleus very dense……. Composed of Protons & Neutrons
Almost all of the mass of an atom is concentrated in the nucleus
A teaspoonful of nuclei packed together would weigh a billion tons

12. Neutrons & Protons Nuetrons- Neutral charged particle found in nucleus
Protons- Positively charged particle found in nucleus, atoms of the same number of protons are atoms of the same element

13. Isotopes
for a given element, the number of neutrons may vary. Isotopes of an element are atoms of the same element having different numbers of neutrons
Example - Uranium-238 (atomic mass 238) has isotope Uranium -235
This was used to make the atomic bomb dropped on Hiroshima

14. Electrons (e-) negatively charged particle not found in the nucleus.
Orbits the nucleus in various energy levels.
In a neutral atom, the number of electrons will match the number of protons
# of electrons in a neutrally charged atom is equal to the # of protons, which is given with the atomic number.
Mass of 1 electron is about 1800 times less than the mass of a proton or neutron

15. Ions
Charged Particle
Positively charged (less electrons than protons)
Negatively charged (more electrons than protons)
not all atoms are neutral. This happens when the number of electrons is more than, or less than the number of protons.
The number of protons never changes,
however the number of electrons can change often.

16. Shell Model of an Atom Electrons occupy different shells.
2 maximum electrons may fit in the first shell
The next shell holds 8 electrons, and the largest shell will hold 50 electrons.
For example, if an atom has 13 electrons, it will have 2 in the first shell, 8 in the second shell, and the remaining 3 will go in the third shell.

17. Periodic Table
chart that lists atoms by their atomic number and by their electron arrangement.
As you move from left to right on chart each element gains one proton and electron .
As you go down each column each element has one more shell filled than the element above.
Elements in the same column are in a Group. Groups have similar properties.

19. Atomic Number - number of protons in the nucleus
Atomic Mass – equals the average mass (in atomic mass units) of the nucleus
# of Protons = Atomic Number
# of Electrons = # of Protons, (if molecule has no charge)
# of Neutrons = (Atomic mass (rounded)) - (atomic number)

20. Phases of Matter
Solid, Liquid, Gas – three familiar states of matter. In all phases, atoms are in constant motion.
The more the molecules move the more fluid they become,
Solid – molecules have least energy, stay fixed relative to each other
Liquid- molecules have more energy, molecules move relative to one another
Gas – molecules have most energy, move with large distances between each other

21. Plasma – the 4th State of Matter
Consists of positive ions and free electrons. Exists only at high temperatures.
What sun and stars are made of. Can be seen here on Earth in the glowing gas of fluorescent lamps.