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. 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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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.