220 likes | 306 Views
Chemical Symbols of Common Elements. Prepare a chart in your notes …. Complete for elements:1-20, 26, 28-30, 35, 47, 50, 53, 79, 80, 82, 92 Use the chart on left to complete the two last columns (only listed elements will have anything for these columns). Mnemonics.
E N D
Chemical Symbols of Common Elements Prepare a chart in your notes …
Complete for elements:1-20, 26, 28-30, 35, 47, 50, 53, 79, 80, 82, 92 Use the chart on left to complete the two last columns (only listed elements will have anything for these columns).
Mnemonics • Mnemonics are ways to help you remember • Used by A students and experts • They are often rhymes or visual connections • E.g. “Thirty days has September, April, June and November, all the rest have 31” • Iron (Fe) … • Iron strong opposite is feeble Fe • A bad mnemonic for Cu is a copper cup (any metal can be made into a cup) • A good mnemonic for Cu is a cup full of pennies • It may seem like more to know, but it works
Mnemonics from Chembored Sodium (Na) Salt? Bad for Blood Pressure (Na, don’t want it) Potassium (K) Kangaroo eating bananas (have potassium)
Mnemonics Iron (Fe) Iron = strong giant = Fe-Fi-Fo-Fum Copper (Cu) A Cup filled with pennies
Mnemonics Mercury (Hg) thermometer goes down = Hug to stay warm Hot gas Lead (Pb) Plumber used lead pipes (not anymore) For more lessons, visit www.chalkbored.com
Mnemonics Silver (Ag) Almost gold Aging = grey hair = silver Tin (Sn) “Tin is Sin” Gold (Au) Always united (wedding ring) Gold = shiny = aura
Quiz yourself on Elements 1-12, sodium, potassium, iron, copper, mercury, lead, silver, tin, gold • 1 Hydrogen • 2 Helium • 3 Lithium • 4 Beryllium • 5 Boron • 6 Carbon • 7 Nitrogen • 8 Oxygen
Quiz Yourself • 9. Fluorine • 10. Neon • 11. Sodium • 12. Magnesium • 26. Iron • 29. Copper • 80. Mercury • 82. Lead
Quiz Yourself 47. Silver 50. Tin 79. Gold
Periodic Table • Periodic Table Rap
Electronegativity + – 0 0 H Cl H H
H H H H H H Na Na Na Na Cl Cl Cl Cl O O O The basic units: ionic vs. covalent • Ionic compounds form repeating units. • Covalent compounds form distinct molecules. • Consider adding to NaCl(s) vs. H2O(s): • NaCl: atoms of Cl and Na can add individually forming a compound with million of atoms. • H2O: O and H cannot add individually, instead molecules of H2O form the basic unit.
Intramolecular forces occur between atoms Intermolecular forces occur between molecules Holding it together Q: Consider a glass of water. Why do molecules of water stay together? A: there must be attractive forces. Intramolecular forces are much stronger • We do not consider intermolecular forces in ionic bonding because there are no molecules. • We will see that the type of intramolecular bond determines the type of intermolecular force.
+ + 0 – 0 – H2 HCl LiCl H H Cl H [Cl]– [Li]+ I’m not stealing, I’m sharing unequally • We described ionic bonds as stealing electrons • In fact, all bonds share – equally or unequally. • Note how bonding electrons spend their time: covalent (non-polar) polarcovalent ionic • Point: the bonding electrons are shared in each compound, but are not always shared equally. • The greek symbol indicates “partial charge”.
Electronegativity • Recall that electronegativity is “a number that describes the relative ability of an atom, when bonded, to attract electrons”. • The periodic table has electronegativity values. • We can determine the nature of a bond based on EN (electronegativity difference). • EN = higher EN – lower EN NBr3: EN = 3.0 – 2.8 = 0.2 (for all 3 bonds). • Basically: a EN below 0.5 = covalent, 0.5 - 1.7 = polar covalent, above 1.7 = ionic • Determine the EN and bond type for these: HCl, CrO, Br2, H2O, CH4, KCl
Electronegativity Answers HCl: 3.0 – 2.1 = 0.9 polar covalent CrO: 3.5 – 1.6 = 1.9 ionic Br2: 2.8 – 2.8 = 0 covalent H2O: 3.5 – 2.1 = 1.4 polar covalent CH4: 2.5 – 2.1 = 0.4 covalent KCl: 3.0 – 0.8 = 2.2 ionic
+ + + – + – – – + – + – Electronegativity & physical properties CaCl2 would have a lower melting/boiling point: CaCl2 = 3.0 – 1.0 = 2.0 CaF2 = 4.0 – 1.0 = 3.0 Note: other factors such as atomic size within molecules also affects melting and boiling points. EN is an important factor but not the only factor. It is most useful when comparing atoms and molecules of similar size. • Electronegativity can help to explain properties of compounds like those in the lab. • Lets look at HCl: partial charges keep molecules together. LiBr would have a lower melting/boiling point: KCl = 3.0 – 0.8 = 2.2 LiBr = 2.8 – 1.0 = 1.8 • The situation is similar in NaCl, but the attraction is even greater (EN = 2.1 vs. 0.9 for HCl). H2S would have a lower melting/boiling point: H2O= 3.5 – 2.1 = 1.4 H2S = 2.5 – 2.1 = 0.4 • Whichwouldhaveahighermelting/boilingpoint? • NaCl because of its greater EN. • For each, pick the one with the lower boiling point a) CaCl2, CaF2 b) KCl, LiBr c) H2O, H2S
CaCl2 would have a lower melting/boiling point: CaCl2 = 3.0 – 1.0 = 2.0 CaF2 = 4.0 – 1.0 = 3.0 Note: other factors such as atomic size within molecules also affects melting and boiling points. EN is an important factor but not the only factor. It is most useful when comparing atoms and molecules of similar size. LiBr would have a lower melting/boiling point: KCl = 3.0 – 0.8 = 2.2 LiBr = 2.8 – 1.0 = 1.8 H2S would have a lower melting/boiling point: H2O= 3.5 – 2.1 = 1.4 H2S = 2.5 – 2.1 = 0.4
– – – – – – – – – + + + + + + + + + + + + + + + + + + Why oil and water don’t mix • Lets take a look at why oil and water don’t mix (oil is non-polar, water is polar) The partial charges on water attract, pushing the oil (with no partial charge) out of the way.