http://www.youtube.com/watch?v=x Tx_DWboEVs http://www.youtube.com/watch?v=5 IJqPU11ngY 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 electron dot structures/diagrams are used to show valence electrons › each dot around the element symbol represents a valence electron 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.phyastr.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 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, 2, 13 , & usually 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- Na Mg N O F Na+ Mg2+ N3- O2- F1- Cations Anions Ne 1+ 2+ 3+ 4+/- 3- 2- 1- 0 ...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) usually composed oppositely charged metallic cations and nonmetallic anions + cations - anions › because of the electrostatic attraction between oppositely charged particles electro- electricity/electrons static- non-moving (vs. current which is moving charges) 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 1.7 or greater to form an ionic bond electronegativty difference 0.0 probable type of bond 0.1 – 1.0 covalent, nonpolar covalent, slightly polar 1.1 – 1.7 >1.7 covalent, very polar ionic Na “gives” Cl one electron and now both atoms have a full valence shell (electron configuration of a noble gas) .9 3 e– 1) 2) Na Cl 3) Na+ Cl– 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 Mg and N? Mg2+, N3 it takes two nitrogens to combine with three magnesiums › Mg3N2 › magnesium nitride Na 1+ + 1F NaF 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 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 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 These will be given on tests NO3-1 nitrate NO2-1 nitrite OH-1 hydroxide ClO2-1 chlorite ClO3-1 chlorate HCO3-1 SO42- hydrogencarbonate (bicarbonate) sulfate SO32- sulfite CO3 2- carbonate PO43- phosphate NH4+ ammonium 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 ? 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 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 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 Fe(NO3)3 Choose the correct name for the compound 1. Iron trinitrate 2. iron(I) nitrate 3. iron(III) nitrite 4. iron(III) nitrate 5. none of the above Periodic Chart Polyatomic Ions next problem sodium chlorite Choose the correct formula for the compound 1. NaCl 2. NaClO 3. NaClO2 4. Na(ClO)2 5. none of the above Periodic Chart Prefixes next problem