Ch2_Atoms - ATOMS AND ELEMENTS TOMS Radioactivity ATOMIC...

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Unformatted text preview: ATOMS AND ELEMENTS TOMS Radioactivity ATOMIC COMPOSITION • Protons • One of the pieces of evidence for the fact that atoms are made of smaller particles came from the work of Marie Curie (1876work Marie 1934). • She discovered radioactivity , She radioactivity the spontaneous disintegration of some elements into smaller pieces. ATOM COMPOSITION The atom is mostly empty space •protons and neutrons in protons the nucleus. the The modern view of the atom was developed by Ernest Rutherford (1871-1937). – + electrical charge – mass = 1.672623 x 10-24 g – relative mass = 1.007 atomic relative mass units (amu) mass • Electrons negative electrical charge – relative mass = 0.0005 amu – • Neutrons no electrical charge – mass = 1.009 amu – Ernest Rutherford Ernest Rutherford Canterbury University in Christchurch, NZ •the number of electrons is equal to the number of protons. •electrons in space around the nucleus. •extremely small. One teaspoon of water has 3 times as many atoms as the Atlantic Ocean has teaspoons of water. Rutherford birthplace, Rutherford birthplace, Nelson, NZ Page 1 The modern view of the atom was developed by Ernest Rutherford (1871-1937). (1871-1937). The modern view of the atom was developed by Ernest Rutherford (1871-1937). (1871-1937). Atomic Number, Z All atoms of the same element have the same number of protons in the nucleus, Z protons 13 Al 26.9815 Mass Number, A • C atom with 6 protons and 6 neutrons is the mass standard • = 12 atomic mass units • Mass Number = # protons + # neutrons protons • A boron atom can have boron A = 5 p + 5 n = 10 amu 10 A 10 Z 5 B Isotopes • Atoms of the same element (same Z) but different mass number (A). • Boron-10 ( 10B) has 5 p and 5 n • Boron-11 ( 11B) has 5 p and 6 n 11B 10B Page 2 atomic number symbol atomic weight Boron in Death Valley Isotopes & Their Uses An MRI image of a guinea pig lung done using “hyperpolarized” helium-3. Ar-129 is helium-3. Ar also used. See civmProjects Periods in the Periodic Table 11B Isotopes 10B • Because of the existence of isotopes, the mass of a collection of atoms has an average value. • Average mass = ATOMIC WEIGHT Average ATOMIC 10 and 11 B. 11 • Boron is 20% 10B and 80% 11B. That is, 11B is Boron 80 percent abundant on earth. • For boron atomic weight = 0.20 (10 amu ) + 0.80 (11 amu) = 10.8 amu Groups in the Periodic Table Periodic Table • Dmitri Mendeleev developed the modern periodic table. Argued that element properties are periodic functions of their atomic weights. • We now know that element properties are periodic functions of their ATOMIC functions ATOMIC NUMBERS. • See CD-ROM, Screen 2.16. Group 1A: Alkali Metals Reaction of potassium + H 2O Cutting sodium metal Page 3 Group 3A: B, Al, Ga, In, Tl Group 4A: C, Si, Ge, Sn, Pb Magnesium Quartz, SiO 2 Magnesium oxide Aluminum Boron halides, BF3 & BI3 from From the Comic Book Periodic Table Diamond Group 5A: N, P, As, Sb, Bi Ammonia, NH 3 White and red phosphorus Page 4 Group 6A: O, S, Se, Te, Po Group 7A: F, Cl, Br, I, At Group 8A: He, Ne, Ar, Kr, Xe, Rn • Lighter than air balloons • “Neon” signs Shuttle main engines use H2 and O2 XeOF 4 Sulfur Transition Elements From the Comic Book Periodic Table Lanthanides and actinides Iron in air gives iron(III) oxide Page 5 ...
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This note was uploaded on 10/19/2011 for the course CHM 2210 taught by Professor Romanmanetsch during the Summer '08 term at University of South Florida - Tampa.

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