Chemical Interactions
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Describe the structure of an atom and define
protons, neutrons, and electrons.
Explain the role of valence electrons in
forming chemical bonds.
Terms: nucleus, protons, neutrons, electrons,
valence electrons, electron dot diagram
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Structure of an Atom
 Atom made of nucleus surrounded by one or more
electrons
 Proton—positively charged
 Neutron—neutral/no charge
 Electron—negatively charged
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Structure of an Atom
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Electrons in Atoms
 Electrons are in an electron cloud around the
nucleus
 Little Particles, Big Spaces
▪ Protons and neutrons make up most of the mass of an
atom
▪ Electrons make up most of the volume of the atom
 Valence Electrons
▪ Outer most electrons
▪ Determines properties and bonding of an atom
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Models
 Dalton—solid ball
 Thomson—plum pudding model
 Rutherford—electrons orbit around the nucleus
 Bohr—electrons are in shells around the nucleus
 Current model—nucleus surrounded by electron
clouds
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Lewis-dot Diagram
 Dots represent valence electrons
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Why Atoms form Bonds
 Atoms are more chemically stable with 8 valence
electrons
 Atoms gain or lose electrons in order to become
chemically stable
 Electrons can be given, accepted, or shared
 When atoms interact new substance are formed
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Periodic Table: organized elements by
increasing atomic number
Atomic Number: number of protons
Group/Family: vertical column on table
 Have similar characteristics
 Have same valence electrons
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Period: horizontal row on table
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Periodic Table: organized elements by
increasing atomic number
Atomic Number: number of protons
Group/Family: vertical column on table
 Have similar characteristics
 Have same valence electrons
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Period: horizontal row on table
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Noble Gases
 Group 18—inactive atoms
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Reactive Nonmetals
 Group 17-Halogens
 Very reactive—need 1 electron
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Reactive Metals
 Group 1-Alkali Metals
 Most reactive metals—give up 1 electron
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Electron Transfer
 Elements gain or lose electrons as they strive to
have eight valence electrons
 When an atom loses an electron—it becomes
positive
 When an atom gains an electron—it becomes
negative
 Ion: atom with a charge
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Forming an Ionic Bond
 Ionic Bond: attraction between two oppositely
charged ions
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Polyatomic Ions
 Ions made of more than one atom
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Naming Ionic Compounds
 Name of positive ion then name of negative ion
 End of name –ide
 For example: Sodium Chloride
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Properties of Ionic Compounds
 All have crystal shape, high melting points, and can
conduct electricity
 Formed between metals and nonmetals
 Crystal Shape
▪ 3-D arrangements of ions called crystals
▪ Ions are attracted to opposite charges and line up in rows
 High Melting Points
▪ Ionic bonds are strong and takes high energy/heat to break
▪ Solid at room temperatures
 Electrical Conductivity
▪ Ions break up when dissolved in a liquid
▪ Moving particles conduct electricity
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Electron Sharing
 Formed when two atoms share electrons
 Form between two or more nonmetals
 Both atoms attract the two shared electrons at
the same time
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How Many Bonds?
 Double Bond: form when two pairs of electrons
are shared
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Properties of Molecular Compounds
 Created with covalent bonds
 Lower melting points than ionic bonds
 Most poor conductors of electricity