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Subatomic Particles in an atom!

Subatomic Particles in an atom!. 3 main particles in the atom: Neutrons Protons Electrons. LOCATION. In physics, we will learn that even these particles are made of smaller particles!. SIZE. Remember, most of an atom is empty space!.

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Subatomic Particles in an atom!

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  1. Subatomic Particles in an atom! • 3 main particles in the atom: • Neutrons • Protons • Electrons LOCATION In physics, we will learn that even these particles are made of smaller particles! SIZE

  2. Remember, most of an atom is empty space! • An atomic model the size of Busch Stadium and parking would contain a pea sized nucleus containing 95.95% of the atoms mass. • The pea at the pitcher’s mound would be the nucleus, and an ant crawling on the parking lot outside would be an electron!

  3. Electrons • JJ Thompson, RA Millikan • Located around nucleus • Negatively (-) charged particles • Mass = essentially zero - only 1/2000 of a proton or neutron • Charge = -1 • Occupies the majority of space in an atom

  4. Protons • Eugen Goldstein (1886) • Located in…. • The tiny, dense nucleus! • Mass of 1.67 x 10-24 grams • We call that 1 amu, or a mass of 1 • Charge = +1

  5. Neutrons • James Chadwick (1932) • Located in…. • The tiny, dense nucleus! • Mass of 1.67 x 10-24 grams • We call that 1 amu, or a mass of 1 • Charge = 0

  6. Nuclear Symbols X = element symbol Z = mass number = # protons + # neutrons A = atomic number = # protons (gives an element its identity!!) So… # neutrons = Z-A Z charge X A

  7. Atomic Number 14 • Number of protons • Number on bottom of symbol • Gives an atom its identity! • If 6 p+ in nucleus, the atom is…. • Carbon! • It 7 p+ in nucleus, the atom is…. • Nitrogen! N 7 12 C 6

  8. How was the atomic number of an element determined? • Henry Moseley, and English scientist, bombarded atoms of elements with high speed cathode rays (electrons!) • He found that the atoms gave off X-rays • He found that there was a pattern between the amount of X-rays given off and the element that gave them off!He theorized that the nucleus of an atom was causing these X-rays to be given off • The more protons in the nucleus, the more x-rays that were given off! • He determined from this exactly how many protons were in the nucleus of each element! • He called the number of protons the atomic number, and he said that this gave an element its identity! • He rearranged the periodic table according to atomic number, and not according to atomic mass! • This cleared up any irregular patterns that were found in the periodic table from before!

  9. Moseley was a great scientist! • He was a physics professor at Oxford University! • Henry Moseley did most of his experimentation when he was only 27 years old! • Unfortunately, he died a year later, in 1915, during World War I. He was killed by a sniper in Turkey! • His short career lasted less than four years…..

  10. Mass Number • Mass Number = number of protons + number of neutrons • Number on the top of the symbol • It tells you the mass of atom! • Not all atoms of the same element weigh the same! • Two atoms of Carbon are shown below. One weighs 12, one weighs 14. • If they are both Carbon, the must both have the same number of….. • Protons! Each has….. • 6 protons! • So different numbers of…. • Neutrons! • How many neutrons does each have? How would we figure that out? • Mass Number - Atomic Number = Number of neutrons 14 12 C C 6 6 6 neutrons! 8 neutrons!

  11. Atoms with same # Protons, but different # neutrons Example– 35Cl and 37Cl are isotopes of chlorine They only differ in their….. Mass! They both have how many protons….? 17! Look at the periodic table, though - the periodic table lists the AVERAGE ATOMIC MASS For chlorine, it is 35.453 amu. This doesn’t look like an average between 35 and 37! That is because they don’t exist in nature 50-50! Chlorine-35 makes up 75.77% of all Chlorine atoms in the universe Chlorine-37 makes up 24.23% of all Chlorine atoms in the universe ISOTOPES

  12. How do we calculate the average atomic mass? Take each atom’s mass number, and multiply by the RELATIVE ABUNDANCE (That is what percentage it is in the universe) You must convert the relative abundance to a decimal Example: (35 amu)(.7577) + (37 amu)(.2423) = 35.4846 amu This is called a weighted average - because you don’t just add and divide by two! ISOTOPES - again….

  13. If # p+ = # e- Then atom is NOT CHARGED Charge = #p+ - #e- If #p > #e- Then + charged (cation) If # p < # e- Then – charged (anion) Electrons and atom charge • ALL ELEMENTS ARE NEUTRAL, AND NOT CHARGED - AN ELEMENT HAS TO REACT IN ORDER TO BE CHARGED! • A CHARGED ATOM IS CALLED AN ION

  14. How many p+, n, e- ?? Ca+2 108 41 Ag 47 20 p+ = e- = n = Charge on atom…. 20 p+ = e- = n = Charge on atom…. 47 18 47 21 61 +2 0

  15. An atom containing 18 e-, 16 P, and 17 N. What element is it?? Atomic number = 16 # p+ = 16 Element is…. Sulfur Number of electrons tells us… There are two more electrons than protons The electrons are winning by 2! Charge is -2! Mass Number = #p+ + #n Write the nuclear symbol for… -2 33 S 16

  16. Which of the following represent isotopes of the same element? 168X 167X 147X 146X 126X Look for same atomic #: (same # protons) 167X and 147X both have 7 protons, so are isotopes of Nitrogen. 146X and 126X both have 6 protons, so are isotopes of C.

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