copyright©2000 by houghton mifflin company. all rights reserved. 1 the modern view of atomic...
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Copyright©2000 by Houghton Mifflin Company. All rights reserved. 3 The Mass and Change of the Electron, Proton, and NeutronTRANSCRIPT
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The Modern View of Atomic Structure
electrons protons: found in the nucleus, they have a
positive charge equal in magnitude to the electron’s negative charge.
neutrons: found in the nucleus, virtually same mass as a proton but no charge.
The The atomatom contains: contains:
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Figure 2.14 Nuclear Atom Viewed in Cross Section
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The Mass and Change of the Electron, Proton, and Neutron
Particle Mass (kg) Charge
Electron 9.11 10 31 1
Proton 1.67 10 27 1+
Neutron 1.67 10 27 0
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ATOMS
• Very dense nucleus containing almost all of the atom’s mass.
• Electrons constitute most of the volume of the atom. Electrons are involved when atoms combine or “bond” to form molecules.
• All atoms contain protons, electrons and neutrons
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ATOMS
• Different atoms have different properties due to different #’s of protons, electrons and neutrons.
• Atomic number (Z) = # of protons
• Mass number (A) = # of protons + # of neutrons
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ISOTOPES
• Atoms with the same # of protons butdifferent # of neutrons.
• Isotopes have almost identical chemical properties since they have the same # of electrons.
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The Chemists’ Shorthand: Atomic Symbols
K Element Symbol39
19
Mass number
Atomic number
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Figure 2.15Two Isotopes of Sodium
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The Chemists’ Shorthand:Formulas
• Chemical Formula:• Symbols = types of atoms• Subscripts = relative numbers of atoms
CO2
• Structural Formula:
• O=C=O
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ION
• Atoms or groups of atoms that has a net positive or negative charge.
• Atoms either gain or lose electrons to acquire a charge.
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Ions
Cation: A positive ionMg2+, NH4
+
Anion: A negative ionCl, SO4
2
Ionic Bonding: Force of attraction between oppositely charged ions.
Salt (Ionic solid): Solid consisting of oppositely charged ions.
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Figure 2.19 Sodium Chloride
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IONS
• Simple Ions: Na+
Cl-
Al3+
N3-
• Polyatomic Ions: Groups of covalently
bonded atoms that carry a charge.
NH4+
CO3-
NO3-
NO2-
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Periodic TableElements classified by: properties
atomic number
Groups (vertical) 1 or 1A = alkali metals 2 or 2A = alkaline earth metals 17 or 7A = halogens 18 or 8A = noble gases
Periods (horizontal)
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Alkali MetalsGroup 1 or Group 1A
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Alkali Metals
• Group 1 or 1A• Metals with low mp• Soft enough to cut with a knife• Form +1 ions when reacting with non-
metals
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Alkaline Earth Metals
• Group 2 or 2A
• Less reactive than Group 1
• Form +2 ions when reacting with non-metals
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Halogens
• Group 17 or 7A or VII A
• Non-metals
• Form -1 ions when reacting with metals
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Noble GasesGroup 18 or Group 8A
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Noble Gases
• Group 18 or 8A or VIII A
• Single atom (monoatomic) gases
• Little reactivity
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Metals, Nonmetals & Mettaloids
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Metals
• Shiny/ metallic luster• Good conductor of heat & electricity• Malleability• Ductile• Tend to lose electrons
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Non-Metals
• Brittle solids• Many gases at room temperature• Liquid – bromine• Poor conductors• Tend to gain electrons• Often share electrons with other non-
metals to form covalent bonds
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Mettalloids
• Some characteristics of metals and some characteristics of non-metals.
• All are solids at room temperature• Semi-conductors of electricity.
• B, Si, Ge, As, Sb, Te, At
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Transition Metals
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Figure 2.21The Periodic Table
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THE END!!!!!!!!!!