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Ionic Bonding

. Formation of Positive Ions (cations). Positive ions are formed when an atom loses one or more valence electronsPositive ions are called cationsReactivity of metals is based on how easily they lose electronsPositive ions are called by the same name as the element. Ex: sodium is still sodi

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Ionic Bonding

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    1. Ionic Bonding

    3. Formation of Positive Ions (cations) Positive ions are formed when an atom loses one or more valence electrons Positive ions are called cations Reactivity of metals is based on how easily they lose electrons Positive ions are called by the same name as the element. Ex: sodium is still sodium. The symbol for a sodium ion is Na+.

    4. Formation of negative ions (anions) Nonmetals gain electrons and form negative ions Negative ions are called anions To designate an anion, the ending –ide is added to the root name of the element. Example-chlorine is the element; chloride is the anion (Cl-) Nonmetals gain the number of electrons needed to equal eight when added to their valence electrons. (Octet Rule)

    5. Main properties of ionic compounds (a.k.a. salts ) All ionic compounds form crystals Ionic compounds tend to have high melting and boiling points Ionic compounds are very hard and very brittle Dry ionic compounds do not conduct electricity Ionic compounds conduct electricity when they dissolve in water (form aqueous solutions) and are called electrolytes

    6. How Ionic Compounds Are Formed Ionic compounds are formed between oppositely charged ions An ion can be a single charged atom (monatomic ion) or a small group of atoms (polyatomic ions) with a charge Binary ionic compounds are composed of two single atom ions (a cation and an anion).

    7. Naming Binary Compounds Binary ionic compounds are named by removing the end of the name from the nonmetal and adding -ide. Sodium and chlorine form sodium chloride Magnesium and oxygen form magnesium oxide Calcium and sulfur form calcium sulfide.

    8. Formula Writing To write the correct formula you must know the charges present on each ion. The positive and negative charges must balance each other in order to have the correct ratio of ions to form a neutral compound. Subscripts are used to indicate the number of ions required in the formula. The number 1 is understood so it is not written in the formula

    9. What are Ionic Bonds? Bond between a metal and nonmetal Solid @ RT and are nonconductors Form salts High mp and bp (strong attraction of particles) Tend to be electrolytes (Ionic compound whose aqueous solution conducts electricity Called “formula units” Strong Attraction between + and - charges

    12. How are ionic compounds written? Write both ions down. Cation then Anion Find oxidation # & put at top right of symbol as a superscript Circle the oxidation #’s, criss-cross them numbers and lose the charge

    13. Example Sodium can form a 1+ charged ion and is written: Na1+ Sulfur can form a 2- charged ion and is written: S2- The formula for sodium sulfide is Na2S

    14. Practice Write the formula for 1. potassium iodide. K+ I- = KI 2. Magnesium bromide Mg2+ Br- = MgBr2 3. Barium nitride Ba2+ N3- = Ba3N2

    15. Polyatomic Ionic Compounds A small group of atoms with a charge is called a polyatomic ion Common polyatomic ions include: nitrate NO31-, sulfate SO42-, carbonate CO32-, bicarbonate (or hydrogen carbonate) HCO31-, and hydroxide OH1- . Notice that the names of these ions end in -ate. When you see a name ending in -ate it probably implies that it is a polyatomic ionic compound.

    16. Polyatomic Ions (Cont’) Polyatomic ions are treated just like a single ion. For example, sodium nitrate needs one 1+ sodium ion to neutralize one 1- nitrate ion, so the formula is NaNO3 If you need more than one polyatomic ion then you put parenthesis around it in the formula. For example, calcium nitrate needs one Ca 2+ ion to neutralize two 1- nitrate ions, so the formula is Ca(NO3)2.

    17. Ions with Multiple Charges Some atoms can commonly form 2 or 3 different charges. These atoms are typically transition elements Copper, for example, usually forms 1+ or 2+ charged ions This can cause problems if a compound is named copper oxide. The formula could be CuO or Cu2O depending on the charge of the copper atom.

    18. continued To clear up this ambiguity, we can name the ions by specifically adding on a number to their name. Cu1+ is copper (I) and Cu2+ is copper (II). So the names of the copper compounds listed above are Copper (II) Oxide for CuO and Copper (I) Oxide for Cu2O.

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