Ionic Bonding Topic 4.1 http://www.youtube.com/watch?v=xTx_DWboEVs http://www.youtube.com/watch?v=5IJqPU11ngY

“Review” Valence electrons electrons in the highest occupied energy level always in the s and p orbitals normally just a draw a circle to represent these two orbitals determines the chemical properties of an element usually the only electrons used in chemical bonds

IB may group levels together and therefore you would see the 3d10 before the 4s2 http://wps.prenhall.com/wps/media/objects/476/488316/Instructor_Resources/Chapter_09/FG09_27-06un.JPG

IB uses this one

Lewis/Electron Dot Diagrams/Structures electron dot structures/diagrams are used to show valence electrons each dot around the element symbol represents a valence electron

Br is [Ar] 4s2 3d10 4p5 How many valence electrons are present? B is 1s2 2s2 2p1; 2 is the outermost energy level it contains 3 valence electrons, 2 in the s and 1 in the p Br is [Ar] 4s2 3d10 4p5 How many valence electrons are present?

http://images.google.com/imgres?imgurl=http://hyperphysics.phy-astr.gsu.edu/hbase/pertab/imgper/econfig.gif&imgrefurl=http://hyperphysics.phy-astr.gsu.edu/hbase/pertab/perlewis.html&h=267&w=512&sz=22&tbnid=__EXctBwlG0J:&tbnh=66&tbnw=128&hl=en&start=1&prev=/images%3Fq%3DElectron%2BDot%2BDiagrams%26svnum%3D10%26hl%3Den%26lr%3D

Ionic Charge when forming compounds, atoms tend to achieve the electron configuration of a noble gas (ns2np6) this means their highest energy level will be filled with 8 electrons that requires the least amount of energy cations atoms of metallic elements (groups 1-14) lose electrons producing cations (positive ions) the term oxidized (O.I.L – Oxidized Is Losing) is used to say it lost an electron example- Ca becomes Ca2+

anions atoms of nonmetallic elements (groups 15, 16, 17) gain electrons producing anions (negative ions) the term reduced (R.I.G.) – Reduction Is Gaining) is used to say it gained an electron example- Cl becomes Cl1-

N O F Ne Na Mg N3- Na+ Mg2+ O2- F1- Cations Anions

1+ 2+ 3+ 4+/- 3- 2- 1-   ...etc. As it turns out, atoms bond together for a very simple reason: atoms that have full valence shells are more stable than those that don’t‘.

some transitional metals can often form more than one cation and therefore charges may vary some orbitals get filled but might not get a noble gas electron configuration iron can be Fe2+ or Fe3+ (you don’t have to memorize this) these always have the same charge Sc3+, Zn2+, Cd2+, Ag1+ (you do have to memorize these)

Formation of Ionic Compounds usually composed oppositely charged metallic cations and nonmetallic anions because of the electrostatic attraction between oppositely charged particles electro- electricity/electrons static- non-moving (vs. current which is moving charges) - anions + cations

forms a compound with overall zero charge (+ and -) need to cancel out referred to as formula units, not a molecule, that is a term used only for covalently bonds which is something different

ions must have a difference in electronegativity of 1 ions must have a difference in electronegativity of 1.7 or greater to form an ionic bond

covalent, slightly polar electronegativty difference probable type of bond 0.0 covalent, nonpolar 0.1 – 1.0 covalent, slightly polar 1.1 – 1.7 covalent, very polar >1.7 ionic

Na “gives” Cl one electron and now both atoms have a full valence shell (electron configuration of a noble gas) 3 .9

e– 1) 2) Na Cl 3) Cl– Na+

Chemical Formula shows the kinds and numbers of atoms in the lowest whole-number ratio of ions in the ionic compound Na 1+ + Cl 1-  NaCl Ca 2+ + Cl 1-  CaCl2 Mg 2+ + O 2-  MgO

it takes two nitrogens to combine with three magnesiums Mg and N? Mg2+, N3- it takes two nitrogens to combine with three magnesiums Mg3N2 magnesium nitride

Na 1+ + F 1-  NaF

Properties of Ionic Compounds high melting and boiling points takes a lot of energy to break apart the electrostatic forces between cations and anions crystalline structure repeating arrays of cations and ions an ionic lattice

volatility- how easily a substance turns into a gas very low as electrostatic forces between cations and anions is very strong electrical conductivity can conduct electric currents when melted or dissolved in water because cations and anions are free moving instead in a lattice solubility will dissolve in other polar solvents such as water

Naming Ions and Writing Ionic Compounds

Naming Ions Monoatomic ions cations lose valence electrons and therefore are positively charged transition metals form more than one cation with different ionic charges charge is determined from the # of electrons lost Fe2+ lost two electrons (the 2 in the 4s) Fe3+ lost three electrons (the 2 in the 4s and 1 in the 3d) naming Stock system a Roman numeral is used to show the charge of the transition metal Fe2+ is iron(II) and Fe+3 is iron(III)

anions gain valence electrons and therefore are negatively charged change ending to –ide for the name

Polyatomic ions (look at list) composed of more than one atom that form a single unit/ion with a charge most end with -ite or –ate the –ite ending indicates one less oxygen than the –ate ending ionic charge is the same for both

hydrogencarbonate (bicarbonate) Memorize these! NO3-1 nitrate NO2-1 nitrite OH-1 hydroxide ClO2-1 chlorite ClO3-1 chlorate HCO3-1 hydrogencarbonate (bicarbonate) SO42- sulfate SO32- sulfite CO3 2- carbonate PO43- phosphate NH4+ ammonium

Naming ionic compounds Binary Compounds cation is written first, followed by the anion with and –ide ending Cs2O  cesium oxide SrF2  strontium fluoride CuO  copper(II) oxide oxygen is always 2- and therefore copper will be 2+ Cu2O  copper(I) oxide oxygen is 2- and therefore needed two copper atoms with 1+ charge

SnF2  ? SnS2  ? fluorine is always 1- and therefore tin will be 2+ tin(II) fluoride SnS2  ? sulfur is always 2- and therefore tin will be 4+ tin(IV) sulfide

Writing formulas for ionic compounds write symbol of cation and then anion add subscripts to balance the charges calcium bromide Ca2+ and Br1- is CaBr2 potassium sulfide K+1 and S2- is K2S iron(III) oxide Fe+3 and O2- is Fe2O3

“crisscross” method the ionic charge number of each ion is crossed over and becomes the subscript for the other ion

Compounds with polyatomic ions do same as binary compounds use the name of the polyatomic ion with the mono atomic ion calcium nitrate  ? Ca is 2+ and nitrate is 1- Ca(NO3)2 Li2CO3  ? lithium carbonate

Remember all compounds the total positive charge Names to Formulas aluminum chloride 1. Write symbols of elements 2. Determine number of ions (Al )x(Cl-1)y +3 If there is no Roman Numeral, you must know the oxidation number of the positive ion. What is the Lowest Common Multiple “LCM” of 3 and 1. Do not worry about the sign(+/-) What is the Lowest Common Multiple “LCM” of 3 and 1. Do not worry about the sign(+/-) For aluminum, a 1 is multiplied times the +3 to give a +3 charge For chloride, a 3 is multiplied times the -1 to give a -3 charge x(+3) + y(-1) = 0 Remember all compounds are neutral, thus the total positive charge must equal the total negative charge If there is no Roman Numeral, you must know the oxidation number of the positive ion. This formula says that the +3 charge of one Al atom will cancel the-3 charge from 3 Cl atoms 1(+3) + 3(-1) = 0 Al Cl 1 3 If there is only one atom the “1” is not shown Final Formula Next

Formula to Name No, you do not use prefixes Fe(NO3)3 Choose the correct name for the compound 1. Iron trinitrate No, you do not use prefixes 2. iron(I) nitrate No, you have the wrong oxidation number 3. iron(III) nitrite No, you need to review polyatomic ions 4. iron(III) nitrate Very good, click arrow to continue 5. none of the above No, there is a correct answer Polyatomic Ions next problem Periodic Chart

Choose the correct formula for the compound Name to Formula sodium chlorite Choose the correct formula for the compound 1. NaCl No, you need to review prefixes 2. NaClO No, you need to review prefixes 3. NaClO2 Very good, click arrow to continue 4. Na(ClO)2 No, you have several errors 5. none of the above No, there is a correct answer next problem Prefixes Periodic Chart