Presentation on theme: "Ions and Ionic Bonds. Review Octet Rule Atoms typically gain or lose valence e - so they will have the same e - configuration as a noble gas. Most noble."— Presentation transcript:
Ions and Ionic Bonds
Review Octet Rule Atoms typically gain or lose valence e - so they will have the same e - configuration as a noble gas. Most noble gases have 8 valence electrons. Helium has only 2 valence electrons.
The Octet Rule Na Ne 8 valence electrons 1 valence electron 8 valence electrons
The Octet Rule 8 valence electrons Cl 7 valence electrons Ar 8 valence electrons
The Octet Rule Li He 2 valence electrons 1 valence electron 2 valence electrons
Ionic bonds are a type of chemical bond based on electrostatic forces between two oppositely-charged ions. Ionic Bonds It is basically the transfer of one electron from one atom to another
An ion is an atom or group of atoms that have a charge. Atoms normally have a neutral charge because most often they have the same number of electrons and protons. They become ions by the loss or addition of one or more electrons. This process is called ionization. Ionic Bonds
An ion that has more electrons than protons is called an anion, and an ion that has fewer electrons than protons is called a cation. Ionic Bonds
The name ion was given by a man named Michael Faraday, which comes from a Greek word meaning “to go” or “a goer”. The word anion comes from the Greek word meaning (a thing) “going up” and cation means (a thing) “going down ”. Ionic Bonds
Ionic Compounds Ionic compound (salt) – compound made of cations and anions. cations are formed from metals anions are formed from non-metals Ionic bond – the force that holds an ionic substance together.
Ionic Bonding NaCl NaCl + -
Ionic bonds Occurs when: 1. a metal atom loses an electron and becomes a positive ion 2. a non-metal atom gains the electron and becomes a negative ion 3. the positive and negative attract each other and form a bond
Ionic Bonding + - - + - - + - - + - + - + - + - + - + - + - + - + - + - + - + - + - + - + - +++ + - + - + - + IMPORTANT: Although the ions in a salt are charged, the compound as a whole is not.
How do ionic bonds form Use the criss-cross method Step 1- Identify the metal and non-metal Step 2- Write the symbols Step 3- write the charges Step 4- cross over the charges Step 5- remove the charge (+ -) Step 6- simplify the numbers and get rid of 1’s NOTE: THE OVERALL CHARGE ON IONIC FORMULAS SHOULD ALWAYS EQUAL ZERO!!!!!!
Ionic Formulas Chemical formula – indicates the number and type of atoms in a substance. H 2 O 2 hydrogen atoms + 1 oxygen atom NaNO 3 1 sodium ion + 1 nitrogen atom + 3 oxygen atoms Formula unit – lowest whole-number ratio of ions in a compound. The formula unit for table salt is NaCl. 1 unit of Na + ions per 1 unit of Cl - ions. Formula does not show the charges of the ions.
Ionic Formulas What salt forms when aluminum combines with chlorine? Aluminum has 3 valence electrons. Loses 3 e - to reach octet. Forms Al +3 ion. Chlorine has 7 valence electrions. Gains 1 e - to reach octet. Forms Cl -1 ion. If the compound is neutral, it will take 1 Al +3 ion for every 3 Cl -1 ions. The formula is AlCl 3.
Aluminum + Chlorine Al Cl
Ionic Bonds – Writing Formulas CRISS-CROSS METHOD Oxidation numbers (excluding charge) of each ion trade places to become the subscripts in the formula – must be reduced to lowest whole number ratio; 1’s are not written Ca & S Ca 2 S 2 Al & Cl AlCl 3 3+ 1- 2+ 2- CaS
Writing Ionic Formulas Criss-Cross Method of writing ionic formulas: Criss-cross charges to become subscripts Drop the charges when crossing over. Example: What salt is formed from sodium and sulfur? Na forms +1 ions. S forms -2 ions. Na +1 + S -2 Na 2 S
Writing Ionic Formulas sodium + chlorine calcium + bromine lithium + oxygen aluminum + oxygen magnesium + nitrogen Na +1 + Cl -1 Ca +2 + Br -1 Li +1 + O -2 Al +3 + O -2 Mg +2 + N -3 NaCl CaBr 2 Li 2 O Al 2 O 3 Mg 3 N 2
Writing Ionic Formulas If the subscripts can be reduced, do so. Example: calcium + oxygen Ions: Ca +2 + O -2 Wrong: Ca 2 O 2 Right: CaO Example: lead + oxygen Ions: Pb +4 + O -2 Wrong: Pb 2 O 4 Right: PbO 2
Ionic Bonds – Writing Formulas Sodium and chlorine bond in a 1:1 ratio to form NaCl Calcium and chlorine bond in a 1:2 ratio for form CaCl 2 What determines each ratio & formula? ________________ oxidation numbers
Ionic Bonds – Writing Formulas IonsOxidation NumbersRatioFormula Magnesium & Oxygen Mg 2+ & O 2- 1:1MgO Lithium & Sulfur Aluminum & Oxygen Sodium & Phosphorus Barium & Fluorine Try to predict the ratio and resulting formula for each of the following ions based on their oxidation numbers: Li + & S 2- 2:1 Li 2 S Al 3+ & O 2- 2:3 Al 2 O 3 Na + & P 3- 3:1 Na 3 P Ba 2+ & F - 1:2 BaF 2
We will learn how to write nomenclature for: Ternary Salts 3 or more elements Includes a polyatomic ion Salts with Multiple Oxidation Numbers Can be binary or ternary Includes a transition metal
Polyatomic Ions Polyatomic Ions – ions made of more than one atom. Examples: NO 3 -1 1 nitrogen atom and 3 oxygen atoms that collectively have a -1 charge. SO 4 -2 1 sulfur atom and 4 oxygen atoms that collectively have a -2 charge. PO 4 -3 1 phosphorus atom and 4 oxygen atoms that collectively have a -3 charge. NH 4 +1 1 nitrogen atom and 4 hydrogen atoms that collectively have a +1 charge.
Polyatomic Ions in Salts Treat them like single-atom ions. But do not change their formula! If you need more than one of a particular polyatomic ion, use parentheses. Example: Na +1 + NO 3 -1 NaNO 3 Mg +2 + NO 3 -1 Mg(NO 3 ) 2 Al +3 + NO 3 -1 Al(NO 3 ) 3
Polyatomic Ions in Salts K +1 + OH -1 Ca +2 + OH -1 Ga +3 + OH -1 NH 4 +1 + Cl -1 NH 4 +1 + S -2 NH 4 +1 + P -3 NH 4 +1 + SO 4 -2 KOH Ca(OH) 2 Ga(OH) 3 NH 4 Cl (NH 4 ) 2 S (NH 4 ) 3 P (NH 4 ) 2 SO 4
Polyatomic Ions NameFormula acetateC 2 H 3 O 2 - or CH 3 COO - ammoniumNH 4 + carbonateCO 3 2- chlorateClO 3 - chloriteClO 2 - chromateCrO 4 2- cyanideCN - dichromateCr 2 O 7 2- hydrogen carbonateHCO 3 - hydroxideOH - hypochloriteClO - nitrateNO 3 - nitriteNO 2 - perchlorateClO 4 - permanganateMnO 4 - phosphatePO 4 3- sulfateSO 4 2- sulfiteSO 3 2- Some ions contain more than one element - called a polyatomic ion The group as a whole has an overall charge Examples: Lithium and sulfate would bond together to make Li 2 SO 4 Ammonium and sulfur would bond together to make (NH 4 ) 2 S
Ternary Salt Naming Contains 3 or more elements: cation & anion – most polyatomic ions are anions, only cation is ammonium (NH 4 + ) Naming: Name the cation (no changes) Name the anion (no changes) Example: Na 2 SO 4 = sodium sulfate Exception: When ammonium is paired with an element anion NH 4 Cl = ammonium chloride
Ternary Salt Formulas You must use parentheses if you have more than one polyatomic ion. Be sure to criss-cross the oxidation numbers and write it OUTSIDE of the parentheses. K & PO 4 K 3 PO 4 Al & SO 3 Al 2 (SO 3 ) 3 3+ 2- + 3-
Ternary Salt Formulas & Naming Ions Oxidation Numbers RatioFormulaName Potassium & Hydroxide K + & OH - 1:1KOH potassium hydroxide Calcium & Carbonate Barium & Nitrate Sodium & Phosphate Ammonium & Sulfur Try to predict the formulas and names for each ternary salt: Ca 2+ & CO 3 2- 1:1 CaCO 3 calcium carbonate Ba 2+ & NO 3 - 2:1 Ba(NO 3 ) 2 barium nitrate Na 3 PO 4 Na + & PO 4 3- 1:3 sodium phosphate NH 4 + & S 2- 1:2(NH 4 ) 2 S ammonium sulfide
Salts with Multiple Oxidation #s Naming Transition elements can form more than one type of positive ion. For example, copper can form both Cu + and Cu 2+ ions, and iron can form both Fe 2+ and Fe 3+ ions. Zinc and silver are two exceptions – they only have one oxidation number The zinc ion is Zn 2+ and the silver ion is Ag +.
Salts with Multiple Oxidation #s Naming Transition elements can form more than one type of positive ion. Naming: Name the cation Put the roman numeral representing the oxidation # of the metal in parentheses (do not indicate the charge) Name the anion, changing the ending to “ide” (binary) or naming the polyatomic ion (ternary) Example: FeCl 2 = iron (II) chloride FeCl 3 = iron (III) chloride
Salts with Multiple Oxidation Numbers Practice Ions Oxidation Numbers RatioFormulaName Copper & Nitrate Cu + & NO 3 - 1:1CuNO 3 copper (I) nitrate Lead & Oxygen Cobalt & Hydroxide Nickel & Phosphate Chromium & Sulfur Pb 4+ & O 2- 2:1 PbO 2 lead (IV) oxide Co 3+ & OH - 3:1 Co(OH) 3 cobalt (III) hydroxide Ni 2+ & PO 4 3- 2:3 Ni 3 (PO 4 ) 2 nickel (II) phosphate Cr 2+ & S 2- 1:1 CrS chromium (II) sulfide