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http://www.youtube.com/watch?v=x Tx_DWboEVs http://www.youtube.com/watch?v=5 IJqPU11ngY
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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
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http://wps.prenhall.com/wps/media/objects/476/488316/Instructor_Resources/Chapter_09/FG09_27-06un.JPG IB may group levels together and therefore you would see the 3d 10 before the 4s 2
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IB uses this one
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electron dot structures/diagrams are used to show valence electrons › each dot around the element symbol represents a valence electron
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B is 1s 2 2s 2 2p 1 ; › 2 is the outermost energy level › it contains 3 valence electrons, 2 in the s and 1 in the p Br is [Ar] 4s 2 3d 10 4p 5 How many valence electrons are present?
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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
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when forming compounds, atoms tend to achieve the electron configuration of a noble gas (ns 2 np 6 ) › 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 Ca 2+
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› 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 Cl 1-
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NeN Na F Na Na + O O O 2- Mg Mg Mg 2+ CationsAnions N N 3- F F 1-
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...etc. As it turns out, atoms bond together for a very simple reason: atoms that have full valence shells are more chemically stable than those that don’t‘. 1+2+ 3-3+4+2-1-0
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› 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 Fe 2+ or Fe 3+ (you don’t have to memorize this) these always have the same charge Al 3+, Sc 3+, Zn 2+, Cd 2+, Ag 1+ (you do have to memorize these)
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3+ 2+ 1+ 2+ 3+ = charge will vary except “x”
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usually composed of 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) + cations - anions
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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
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ions must have a difference in electronegativity of 1.7 or greater to form an ionic bond
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0.1 – 1.0 1.1 – 1.7 >1.7 0.0covalent, nonpolar covalent, slightly polar covalent, very polar ionic electronegativty difference probable type of bond
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Na Cl e–e– 1) 2) 3) Na + Cl –
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shows number of each element in the lowest whole-number ratio of ions in the ionic compound › Na 1+ + Cl 1- NaCl › Ca 2+ + Cl 1- CaCl 2 › Mg 2+ + O 2- MgO
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Mg and N? Mg 2+, N 3- it takes two nitrogens to combine with three magnesiums › Mg 3 N 2 › magnesium nitride
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Na 1+ + F 1- NaF
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cations transition metals form more than one cation with different ionic charges › charge is determined from the # of electrons lost Fe 2+ lost two electrons (the 2 in the 4s) Fe 3+ 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 Fe 2+ is iron(II) and Fe +3 is iron(III)
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› anions gain valence electrons and therefore are negatively charged change ending to –ide for the name
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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
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Memorize these! NO 3 1- nitrate NO 2 1- nitrite OH 1- hydroxide ClO 2 1- chlorite ClO 3 1- chlorate HCO 3 1- hydrogencarbonate (bicarbonate) SO 4 2- sulfate SO 3 2- sulfite CO 3 2- carbonate PO 4 3- phosphate NH 4 1+ ammonium
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Binary Compounds › cation is written first, followed by the anion with and –ide ending Cs 2 O cesium oxide SrF 2 strontium fluoride transitional metals are more difficult CuO copper(II) oxide oxygen is always 2- and therefore copper will be 2+ Cu 2 O copper(I) oxide oxygen is 2- and therefore needed two copper atoms with 1+ charge
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› SnF 2 ? fluorine is always 1- and therefore tin will be 2+ tin(II) fluoride › SnS 2 ? sulfur is always 2- and therefore tin will be 4+ tin(IV) sulfide
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write symbol of cation and then anion add subscripts to balance the charges › calcium bromide Ca 2+ and Br 1- is CaBr 2 › potassium sulfide K +1 and S 2- is K 2 S › iron(III) oxide Fe +3 and O 2- is Fe 2 O 3
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the ionic charge number of each ion is crossed over and becomes the subscript for the other ion
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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(NO 3 ) 2 Li 2 CO 3 ? lithium carbonate
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aluminum chloride Al Cl 3 2. Determine number of ions 1. Write symbols of elements Final Formula x(+3) + y(-1) = 0 1 For aluminum, a 1 is multiplied times the +3 to give a +3 charge If there is only one atom the “1” is not shown If there is no Roman Numeral, you must know the oxidation number of the positive ion. +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(+/-) (Al ) x (Cl -1 ) y What is the Lowest Common Multiple “LCM” of 3 and 1. Do not worry about the sign(+/-) For chloride, a 3 is multiplied times the -1 to give a -3 charge 1(+3) + 3(-1) = 0 Remember all compounds are neutral, thus the total positive charge must equal the total negative charge Next This formula says that the +3 charge of one Al atom will cancel the-3 charge from 3 Cl atoms
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Fe(NO 3 ) 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 next problem Polyatomic Ions Periodic Chart
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sodium chlorite Choose the correct formula for the compound 1. NaCl 2. NaClO 3. NaClO 2 4. Na(ClO) 2 5. none of the above next problem Prefixes Periodic Chart
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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
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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
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