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Two types of chemical bonds are Ionic Bonds and Covalent Bonds Chemical Bonding: Covalent Bonding
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Chemical Bonds Two types of chemical bonds are Ionic Bonds and Covalent Bonds
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Covalent Bonding The chemical bond formed when two atoms share electrons Covalent means “share” Way to remember: “CO” – together like a couple or companion Way to remember: “VALENT”– valence electrons What is the difference between a covalent bond and an ionic bond? Electron sharing occurs when atoms such as Hydrogen bond to other nonmetals or with the same element
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Covalent Bonding By sharing electrons, each atom has a stable set of eight The force that holds atoms together in a covalent bond is the attraction of each atom’s nucleus for the shared pair
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Covalent Bonding: Molecules What is a molecule? Neutral group of atoms joined by covalent bonds Ex. 2 Fluorine atoms form a Fluorine molecule
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Covalent Bonding Except for Hydrogen, the number of covalent bonds that nonmetal atoms can form equals the number of electrons needed to make a total of eight Ex. Nitrogen has 5 valence electrons and Hydrogen has 1 valence electron
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Covalent Bonding Double bonds are when two atoms share two pairs of electrons Ex. CO2 Triple bonds are when atoms share three pairs of electrons Ex. Nitrogen What is the difference between a double bond and a triple bond? A double bond shares 4 electrons and a triple bond shares 6 electrons
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Covalent Bonding: Molecular compounds What is a molecular compound? A molecular compound is a compound that is composed of molecules The molecules of a molecular compound contain atoms that are covalently bonded What are the properties of molecular compounds? Low melting points and boiling points Do not conduct electricity when dissolved in water
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Covalent Bonding: Molecular Compounds What is unequal sharing of electrons? Atoms of some elements pull more strongly on shared electrons than do atoms of other elements As a result, the electrons are pulled more towards one atom, causing the bonded atoms to have slight electrical charges which are not as strong as the charges on ions
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Covalent Bonding Polar Bonding A covalent bond in which electrons are shared unequally The unequal sharing of electrons is enough to make the stronger pull slightly negative and the weaker pull slightly positive Ex. H2O Nonpolar Bonding A covalent bond in which electrons are shared equally If two atoms pull equally on the electrons, neither atom becomes charged Ex. F2
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Covalent Bonding: Bonding in Metals What is an alloy? Mixture made of two or more elements that has the properties of a metal In every alloy, at least one of the elements is a metal Alloys are generally stronger and less likely to react with water than are the pure metals from which they are made
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Covalent Bonding: Metallic Bonding What is a metallic bond? An attraction between a positive metal ion and the electrons surround it Metals are in group 1, 2, and 3 so they lose electrons easily because their valence electrons are not strongly held Each metal ion is held by a metallic bond The more valence electrons an atom can add, the stronger the metallic bond will be
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ADD THE FOLLOWING NOTES TO YOUR PREVIOUS COVALENT BOND NOTES. YOU WILL WRITE DOWN THE FOLLOWING NOTES. THEY ARE NOT FILL-IN-THE-BLANK. YOU MAY HAVE TO USE A NEW SHEET OF PAPER.
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Covalent Bonding Attraction between neutral atoms Formed by sharing e - between two nonmetals Cl
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Covalent Bonding Covalent bonds result in discrete molecules Cl 2 H2OH2O NH 3
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Nonpolar Covalent Bonds e - are shared equally usually identical atoms Ex: Carbon Dioxide Covalent Bonding (-) (+) (-) Opposite pulling cancels out CO 2
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Polar Covalent Bonds e - are shared unequally between 2 different atoms results in partial opposite charges Ex: Water Covalent Bonding H2OH2O (-) (+)
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Covalent Bonding Sharing Electrons:
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H2OH2O 2 hydrogen atoms 1 oxygen atom Shows: 1) elements in the compound 2) ratio of their atoms Covalent Bonding
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Nonpolar Polar Ionic Covalent Bonding
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Ionic and Covalent Bonds Comparison Chart IONIC COVALENT Electrons Melting Point Soluble in Water Conduct Electricity Other Properties transferred from metal to nonmetal high yes (solution or liquid) yes crystal lattice of ions, crystalline solids shared between nonmetals low no usually not molecules, odorous liquids & gases
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