Ions In general, atoms are electrically neutral They have the same number of protons (+) as electrons (-) However, because atoms can gain or lose electrons, they can become charged.

These atoms lose electrons These atoms gain electrons IONS An atom or a group of atoms that have gained or lost electrons (it has a charge) 2 types ANIONS (negative ions) CATIONS (positive ions) These atoms lose electrons These atoms gain electrons Ex. Na1+ Ex. Cl1-

TYPES OF BONDS Example 1. IONIC BONDS – formed between oppositely charged ions (ex. between a metal and nonmetal) -forms when electrons are transferred from one atom to another Example Na+1 combined with Cl-1 NaCl

Ionic Bonding NaCl 1st: Na gives up an electron to Cl 2nd: Forming Na+ & Cl- 3rd: Oppositely charged ions attract & form a “bond” NaCl http://enstrophy.colorado.edu/~mohseni/ASEN5519Spring2004/TypesOfChemicalBonds1.html

http://www.visionlearning.com/library/module_viewer.php?mid=55 Sodium (Na) loses its one valence electron to Chlorine (Cl) resulting in Na Cl A negatively charged Cl ion (-1) A positively charged Na ion (+1) Na Cl

Ionic Bonding CaBr2 - Br Ca - Br 1st: Ca gives up an electron to each Br Ionic Bonding 2nd: Forming Ca2+ & two Br- 3rd: Oppositely charged ions attract & form a “bond” Br - Ca 2+ Br - CaBr2

Important! When compounds formed by ionic bonds are dissolved in water, the solution will conduct electricity Why? Ions in solution are mobile & carry a charge, therefore can carry an electric current

TYPES OF BONDS 2. COVALENT BONDS Examples -forms when electrons are shared between the atoms -formed between two non-metals. Examples Cl2 H2 CO

1st: Both Cl have a strong affinity for their valence electrons Covalent Bonding 2nd: So both Cl atoms share a valence electron 3rd: Forming a “bond” http://enstrophy.colorado.edu/~mohseni/ASEN5519Spring2004/TypesOfChemicalBonds1.html

Cl2 is an example of covalent bonding. http://wine1.sb.fsu.edu/chm1045/notes/Bonding/Covalent/Bond04.htm Cl2 is an example of covalent bonding. The chlorine atoms each share one of their valence electrons, Their outermost shell is now full (it is stable) H2 is another example of covalent bonding. The hydrogen atoms each share their valence electron with one another. Their outermost shell is now full (recall in the first shell there are only 2 valence electrons!)  

1st: Both C & H have a strong affinity for their valence electrons Covalent Bonding 2nd: So all atoms share their valence electron, forming a “covalent bond”

1st: Both O & H have a strong affinity for their valence electrons Covalent Bonding 2nd: So all atoms share their valence electron, forming a “covalent bond”

Important! When compounds formed by covalent bonds are dissolved in water, the solution will NOT conduct electricity Why? There are no ions or free charges present, so no electricity can be conducted

Recall – ionic bonds are Ex #1 Which of the following compounds have ionic bonds? 1. MgCl2 2. Al2O3 3. SO2 4. CH4 5. BeF2 6. SiO2 Recall – ionic bonds are formed between a metal & non-metal

Recall – covalent bonds Ex #2 Which of the following compounds have covalent bonds? 1. C2H6 2. P2O5 3. NH3 4. Li2S 5. F2 6. AlCl3 Recall – covalent bonds are formed between non-metals or metalloid & non-metal

Ex #3 Which of the following compounds when dissolved in water will produce an electrolytic solution? 1. C6H12O6 2. H2S 3. C2H4OH 4. MgCl2 5. AlBr3 Recall – ionic compounds when dissolved in water will conduct electricity

Ex #4 Which of the following compounds when dissolved in water will NOT form ions? 1. Fe2O3 2. H2 3. Ca(OH)2 4. MgS 5. NO2 Recall – only ionic compounds when dissolved in water will form ions

Same as ions except they are in groups instead of single atoms POLYATOMIC IONS A group of elements bonded together to form a single ion with their own charge Same as ions except they are in groups instead of single atoms

POLYATOMIC IONS Ex. OH_ (hydroxide ion) It has a charge of 1- Consists of an oxygen atom and a hydrogen atom Treated like one single ion even though it is made up of 2 atoms

POLYATOMIC IONS Ex. SO42- (sulfate ion) It has a charge of 2- Consists of a sulfur atom and four oxygen atoms

Other polyatomic ions... Charge on ion http://www.hcc.mnscu.edu/programs/dept/chem/V.12/page_id_23714.html

You must memorize the following names and charges for these polyatomic ions: OH-1 Hydroxide NH4+1 Ammonium SO4-2 Sulfate CO3-2 Carbonate PO4-3 Phosphate NO3-1 Nitrate

How do we write formulas using polyatomic ions??? MOLECULAR FORMULAS How do we write formulas using polyatomic ions??? Ex. Na1+ SO42- Sodium sulfate Na2SO4 Treat the polyatomic ion as a single item & note the charge (sulfate has a charge of 2-) 2. Note the charge on the other element (sodium (Na) has a charge of 1+) 3. Use the crossover rule to find the formula (Na2SO4)

MOLECULAR FORMULAS Ex. Magnesium Hydroxide Mg2+ OH1- Mg(OH)2 Treat the polyatomic ion as a single item & note the charge 2. Note the charge on the other element 3. Use the crossover rule to find the formula

MOLECULAR FORMULAS Ex. Lithium Phosphate Li+ PO43- Li3PO4 Treat the polyatomic ion as a single item & note the charge 2. Note the charge on the other element 3. Use the crossover rule to find the formula

MOLECULAR FORMULAS Ex. Calcium Carbonate Ca2+ CO32- CaCO3 Ca2(CO3)2 Treat the polyatomic ion as a single item & note the charge 2. Note the charge on the other element 3. Use the crossover rule to find the formula

MOLECULAR FORMULAS Ex. Ammonium bromide NH4+ Br- NH4Br Treat the polyatomic ion as a single item & note the charge 2. Note the charge on the other element 3. Use the crossover rule to find the formula

PRACTICE PROBLEMS Worksheet # 1 Study guide, Module 3, page 8 and 9