Do Now: Pass in homework to be peer graded and returned Objective: 4.3 Distinguishing Atoms Home Work: Pg. 119 # 25 – 29, 32
Indivisible and indestructible • By using experimental methods • Scanning Tunneling Microscope • Protons, Neutrons, and Electrons • A positively charges nucleus surrounded by electrons which take up most of the volume • Proton + 1 , Neutron + 1, Electron – 1/1840 13. So many of the alpha particles went straight through the gold foil. 14. Rutherford had a positively charged dense nucleus that was tiny in comparison with the atom as a whole while Thompson’s “plumpudding” model had electrons that were stuck in the large positive area.
10/10/11 • Indivisible and indestructible 4) All matter is composed of atoms. All atoms of the same element are identical. Chemical change involves rearrangement of atoms in whole number ratios 5) No. 6) 5 x 10-2 nm to 2 x 10-1 nm 8) Protons, neutrons, and electrons 9) A small, positively charged nucleus surrounded by electrons, which take up most of the volume 10) protons, 1, +; neutrons, 1, none; electrons, ~0, -1 11)
Atomic Number • Elements are different because they contain different numbers of protons. Atomic Number =
Atomic Number • Elements are different because they contain different numbers of protons. Atomic Number = the number of protons in the nucleus of an atom of a given element.
Mass Number • Mass Number = The total number of protons and neutrons in the nucleus of an atom
Mass Number • Mass Number = The total number of protons and neutrons in the nucleus of an atom # of Neutrons = Mass Number - Atomic Number Mass Number = # of protons + # of neutrons
Practice problem • What is C.C. Carbon’s mass number? I have 6 protons, 6 neutrons, and 6 electrons. Do I look fat??!!?!?! Mass Number= 6 protons + 6 neutrons = 12 *Never ask a lady about her atomic mass.
Isotopes • Atoms with the same number of protons but different numbers of neutrons are called isotopes. • Carbon-12 = 6 p+ and 6 no • Carbon-13 = 6 p+ and 7 no • Carbon-14 = 6 p+ and 8 no • Same # of protons all are still carbon. I’m prettier!!! We’re almost identical! Carbon-12 Carbon-14
Isotopes • Because isotopes of an element have different numbers of neutrons, they also have different mass numbers • Mass number = # of protons + # of neutrons I’m prettier!!! We’re almost identical! Carbon-12 Carbon-14
Atomic Mass • An Atomic Mass Unit (amu) is defined as 1/12th of the mass of a Carbon-12 atom • 1 amu ≈ mass of a proton or a neutron
Atomic Mass • Why aren’t all the atomic masses on the periodic table whole numbers? • Because they are weighted averages of the mass of isotopes of that element. Example:
Practice Problem! • Calculate the atomic mass of bromine. The two isotopes of bromine have mass numbers and relative abundance of: Br-79: 78.92 amu (50.69%) Br-81: 80.92 amu (49.31%)
The Periodic Table If there are around 117 elements why do you think we organize them as in the Periodic Table and don’t simply list them 1 -117?
The Periodic Table Periods are the horizontal rows Groups are the vertical columns
Friday, October 1 • Do Now – Current Events and Chemistry • Objective – Chapter 4 Review 5.1 Models of the Atom • Homework – Start Pg. 132 # 1-6 (Due Tuesday)