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Characteristics of chemical bonds Metals • What characteristic do metals have in common, as far as their desire to gain or lose electrons? • Metals want to lose electrons • Alkali metals: lose ___ electron • 1 • Alkaline earth metals: lose ___ electrons • 2 • This gives them a ____________ charge • positive Non-metals • What characteristic do non-metals have in common, as far as their desire to gain or lose electrons? • Non-metals want to gain electrons • This gives them a _________ charge • negative Chemical Bonds • Bond – a force that holds two or more atoms together and makes them function as a unit. Opposites attract • When the negatively charged non-metals are attracted to the positively charged metals, they form an … • ionic bond: the attraction between oppositely charged ions. • These ionically bonded ions are called… • ionic compounds: when a metal bonds with a non-metal Properties of ionic compounds • Very high melting and boiling points • Brittle solids • Solids don’t conduct electricity • Water soluble • Highly conductive once melted or dissolved • Solutions are good electrical conductors Bond Energy • You can determine the amount of energy on a bond by testing how much energy it takes to break the bond. • The amount of energy in a bond is called the… • bond energy – duh! Bonding of Similarly Charged Ions • Does hydrogen want to lose or gain electrons? • Gain • How many? • 1 • When 2 hydrogen atoms get close enough to each other, they attract and “share” their one electron each, to give access to the other’s. • The electrons move about both nuclei. • The union that comes from atoms sharing electrons is called a Covalent bond Covalent bonding • Draw the Lewis Dot structure of two hydrogen atoms bonded covalently • How many electrons does each get the impression of having in its valence orbital? • 2 electrons • Draw 2 oxygen atoms bonded covalently • How many electrons does each get the impression of having in its valence orbital? • 8 electrons • Are they “happy”? Polar Covalent Bonding • Now draw the Lewis Dot structure for hydrogen and fluorine atoms bonding covalently • Are they “happy” (full valence)? • Do you think the hydrogen and fluorine nuclei have an equal attraction to the electrons? • Which has more? • Fluorine • This is called polar covalent bonding: • The electrons are not shared equally because one atom has a greater attraction to the shared electrons than the other. Polar Covalent Bonding • The polarity of a bond depends on the difference between the electronegativity values of the atoms forming the bond.
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