2a. Students know atoms combine to form molecules by sharing electrons to form covalent or metallic bonds or by exchanging electrons to form ionic bonds. 2.c. Students know salt crystals, such as NaCl, are repeating patterns of positive and negative ions held together by electrostatic attraction.
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2a. Students know atoms combine to form molecules by sharing electrons to form covalent or metallic bonds or by exchanging electrons to form ionic bonds. 2.c. Students know salt crystals, such as NaCl, are repeating patterns of positive and negative ions held together by electrostatic attraction.
• Chemical Bonds hold atoms together.
1. Ionic Bonds
2. Metallic Bonds
3. Covalent
Review…. • Valence electrons are why the families of the
periodic table have similar chemical properties and reactions.
• Valence e- determine the types of chemical bonds an atom will make!
C
• Shows how many valence electrons (ve-) available for bonding and how many of these electrons are paired
• Non-bonding pairs – paired electrons in an electron-dot structure
• Paired electrons are stable and do not form bonds
• Unpaired valence electrons participate in bonds
• By doing so, they become paired with an electron from another atom.
• Valence electrons can be given, taken, or shared!
• Elements with 8 electrons in the valence shell are unreactive and do not form bonds
• Noble gases have a full octet making them stable or unreactive (inert)
• All elements want to be stable
• losing or gaining ve- allow elements to become stable when they achieve a noble gas configuration
• Metals lose electrons (cation +)
• Nonmetals gain electrons (anion -)
• Ionic Bonds form when metals (cations) and nonmetals (anions) bond!
• Held together by electrostatic attraction (+ and – force)
• Electrical force makes a Strong Bond!
• For all ionic bonds…+ and – charges must balance!
• This means that all + charges must equal every – charges
• Charges must also balance in compounds containing ions that carry multiple charges.
• Ex. Calcium ion has a charge of 2+ but the fluoride ion has a 1- charge. Two fluoride ions are needed to balance each calcium ion, the formula for calcium fluoride is CaF2.