1. Learning Goal #3: Discriminate between the relative size, charge, position, and number of protons, neutrons, and electrons of different elements.

2.  Atom: the smallest unit of matter that retains the identity of the substance

3.  http://learn.genetics.utah.edu/content/begin/cells/scale/ http://learn.genetics.utah.edu/content/begin/cells/scale/  The nucleus has a diameter 10,000 times smaller than the atom. The great amount of empty space in an atom can be illustrated by the following analogy.  Imagine the nucleus to be the size of a golf ball. Then on this scale the first electron shell would be about one kilometer from the golf ball, the second shell about four kilometers, the third nine kilometers and so on. If you find that hard to visualize then try this. The period at the end of this sentence, (depending on your monitor and the font you are using), is probably about 1/2 a millimeter in diameter. If that period represents the nucleus then the electrons in the first shell would be orbiting with a diameter about 50 meters around you. in fact, the actual diameter of an atom is very small and it would require some two hundred million of them side by side to form a line a centimeter long.

4.  You are probably familiar with the textbook diagram of an atom that fits neatly on the page. However, the reality will get you thinking how really empty space is:  If a proton were the size of a marble an electron would be about the width of a human hair. With that scale the electron's orbit would be about 2 1/2 miles away from the proton.

5.  Atoms are composed of 2 regions:  Nucleus: the center of the atom that contains the mass of the atom  Electron cloud: region that surrounds the nucleus that contains most of the space in the atom Nucleus Electron Cloud

6. The nucleus contains 2 of the 3 subatomic particles: Protons: positively charged subatomic particles Neutrons: neutrally charged subatomic particles The 3 rd subatomic particle resides outside of the nucleus in the electron cloud Electron: the subatomic particle with a negative charge and relatively no mass

7. Atomic Particles ParticleChargeMass #Locationsymbol Electron0Electron cloud e-e- Proton+11Nucleus p+p+ Neutron01Nucleus n0n0

8.  Protons and neutrons live compacted in the tiny positively charged nucleus accounting for most of the mass of the atom  The negatively charged electrons are small and have a relatively small mass but occupy a large volume of space outside the nucleus

9.  In an atom:  The # of protons = The # of electrons  If 20 protons are present in an atom then 20 electrons are there to balance the overall charge of the atom—atoms are neutral  The neutrons have no charge; therefore they do not have to equal the number of protons or electrons

10.  An atom with 6 protons = Carbon  An atom with 8 protons = Oxygen  An atom with 20 protons = Calcium

11. ATOMIC STRUCTURE the number of protons in an atom the number of protons and neutrons in an atom He 2 4 Atomic mass Atomic number Number of electrons = Number of protons Number of neutrons = Atomic mass – Number of protons

12.  Li has a mass number of 7 and an atomic number of 3  Protons = 3 (same as atomic #)  Neutrons= 7-3 = 4 (mass # - atomic #)  Ne has a mass number of 20 and an atomic number of 10  Protons = 10  Neutrons = 20 - 10= 10

13.  The electrons are equal to the number of protons  So e - = p = atomic #  Ex: He has a mass # of 4 and an atomic # of 2  p + = 2  n o = 2  e - = 2

14.  Cl has a mass # of 35 and an atomic # of 17  p + = 17,n o = 18, e - = 17  K has a mass # of 39 and an atomic # of 19  P + = 19,n o = 20e - = 19

15.  Bohr Model of the atom: Reviewers think this could lead to misconceptions! All of the protons and the neutrons The 1 st ring can hold up to 2 e - The 2 nd ring can hold up to 8 e - The 3 rd ring can hold up to 8 e - The 4 th ring and any after can hold up to 18 e -

16. ATOMIC STRUCTURE Electrons are arranged in Energy Levels or Shells around the nucleus of an atom. first shella maximum of 2 electrons second shella maximum of 8 electrons third shell a maximum of 8 electrons

17. Mass # = 12 atomic # = 6 p + = 6 n o = 6e - = 6 6 p and 6 n live in the nucleus

19.  A unit created to describe atoms because the gram and kilogram are too large to use to define an atom.  1amu = 1.66 x 10 -24 g .00000000000000000000000166g

20.  Listed on the periodic table as the atomic mass.  The average mass of all of the isotopes of an atom. Elementamu Hydrogen1.008 Carbon12.01 Nitrogen14.01 Oxygen16.00 Sodium22.99 Aluminum26.98

21.  1 atom = 1 amu  Example › 1 atom of carbon = 12.001 amu of carbon › 3 atoms of carbon = 36.003 amu of carbon › 3.00 X 10 20 amu =2.50 x 10 19 atoms of carbon

22.  The unit all chemists use in describing numbers of atoms.  Defined as the number equal to the number of carbon atoms in 12.01 grams of carbon.  A sample of on element with a mass equal to that element’s average atomic mass expressed in grams contains 1 mol of atoms.

23.  6.022 X 10 23  One mole of something consists of 6.022 X 10 23 units of that substance. › One mole of eggs is 6.022 X 10 23 of eggs. Elements# of atoms Mass of sample (g) Aluminum6.022 X 10 23 26.98 Gold6.022 X 10 23 196.97 Iron6.022 X 10 23 55.85 Sulfur6.022 X 10 23 32.07 Boron6.022 X 10 23 10.81 Xenon6.022 X 10 23 131.3

24.  The mass of one mole of a substance. › The sum of all the masses of the atoms in a compound. CH 4  C - 1x12.01=12.01  H – 4x1.008=4.032  Total = 16.04g