Unformatted text preview: Molecularity Molecularity CH1010
Lecture 3 James P. Dittami Introduction to the Periodic Table Introduction to the Periodic Table The modern periodic table. The Periodic Table Periodic Table Collection of All known elements arranged in Table and each represented by a symbol in a box Number above each symbol = Atomic no. Atomic No. = # Protons Number below element = MASS From Mass & Atomic No we get# neutrons Periodic Table Periodic Table Element Boxes are arranged into the form of a grid or Table We refer to rows of boxes as Periods The columns of boxes are referred to as Groups The eight A groups (2 on left and 6 on right comprise the Main Group Elements Those in the middle labeled “B” are the Transition Elements Metals Metals Most Elements are “Metals” Metals tend to lose electrons to give positively charged species or Cations Efficient Conductors of Heat/ Electricity Malleable Ductile Lustrous Metals except for H Occur to the Left except of the Solid Line Staircase of NonMetals NonMetals NonMetals Appear in the upper right to the right of the solid line stair case NonMetals also include Hydrogen – H NonMetals tend to gain electrons to form negatively charged species called Anions Non Metals which include H Occur to the RIght of the Solid Line Staircase RIght Metalloids Metalloids Metalloids – show properties of both metals and nonmetals These occur along the solid line staircase The modern periodic table. The Groups or Families of Elements Groups or Families of Elements Vertical Columns of elements comprise Groups or Families of Elements They display similar properties Some groups have names Traditional names 1A, 2a etc. Group 1 Alkalai metals all form+1 cations Group 2 – Alkaline Earth Metals form +2 ions Group 7 Halogens form 1 Anions Group 8 – Noble Gases Generally inert The modern periodic table. The Molecules and Bonding Molecules and Bonding Atoms in a molecule are held together by bonds We can represent the molecule in different ways to give a better picture of bonding.
Empir ical For mulas H 2O Chemical For mulas H 2O Str uct ur al For mul as H O H C 2H6O C 2H6O HH HCCO HH H HO H 2O2 OO H H Bonding Bonding Ionic Covalent Compounds Elements gain or lose electrons to form ions Anion + Cation attract to form ionic bond Binary Ionic Compounds have 2 elements Elements come together and share electrons Usually nonmetals H2, O2, CH4 etc. Elements in Nature Elements in Nature Few Occur free in nature Some occur bonded to same type He, Ne, Ar, Kr, Xe –The Noble Gases Rn/ Cu, Ag, Au, Pt O2, N2, Br2, S8 etc. Most are bonded to some other element Why form Ions? Why form Ions? Many Compounds gain or lose electrons to form () Anions or (+) Cations In general they gain or lose electrons to get to the electronic configuration of the closest Noble gas He, Ne, Ar etc. Recall Noble gases are inherently stable!! The modern periodic table. The Some common monatomic ions of the elements. Some The modern periodic table. The Figure 2.14 The relationship between ions formed and the nearest noble gas. Ionic Compounds Ionic Compounds Binary Ionic Compounds Can form between Polyatomic ions Formed Between two atoms a metal and non metal e.g. Cesium Fluoride, Lithium Bromide NH4+, CO32 etc. Ionic Compounds are neutral – no net charge Covalent Compounds Covalent Compounds Usually form between non metals Diatomic molecules H2, N2, O2, Br2 HF, H2S, PCl5 Covalent species exist as “molecules” Ionic species exist as “ion pairs” Formation of a covalent bond between two H atoms.
Covalent bonds form when elements share electrons, which usually occurs between nonmetals. Naming Compounds Naming Compounds We will use a fool proof method with a flow chart for naming compounds!! We will look at classes of compounds Binary Ionic Type I Binary Ionic Type II Ionic Compounds with Polyatomic Ions Covalent Compound Type III Acids and Oxyanions Naming Ionic Compounds Naming Ionic Compounds Binary Ionic Type I Metals which form only a single cation e.g. Na+, Mg2+, Ca2+ Binary Ionic Type II Metals which form more than one cation e.g. Fe2+, Fe3+ and Pb2+, Pb4+ Ionic Compounds with Polyatomic Ions Binary Ionic (Type I) Binary Ionic (Type I) Monatomic Ion metal only forms a single cation Name Cation first using element name Name Anion last using root + ide Alkalai metals e.g. Na+ (Group 1) Alkaline earth metals e.g. Mg+2 (Group 2) Also Ag+, Zn2+, Cd2+ NaCl = Sodium Chloride CsBr = Cesium Bromide SrF2 = Strontium Fluoride Common Monatomic Cations Common Monatomic Cations and Anions Binary Ionic (Type II) Binary Ionic (Type II) Metals that can form multiple cations: Fe2+, Fe3+ FeCl2 = Iron (II) Chloride Use Roman Numeral to Specify Charge FeCl3 = Iron (III) Chloride Binary Ionic (Type II) Binary Ionic (Type II) Older nomenclature –ic and –ous FeCl2 = Ferrous Chloride (Lower Charge) FeCl3 = Ferric Chloride (Higher Charge) Fe2+– Lower Charge Use ous Fe3+– Higher Charge Use ic Table 2.4 Table 2.4 Common Type II Cations Things to note Things to note Most Type I are Group IA and IIA also Al3+ Most Type II are transition metals Ag+, Zn2+, Cd2+ are transition metals but only form one cation so treat as Type I no Roman Numeral is necessary. Mercury Hg, forms Hg(I) and Hg(II). But Hg(I) always occurs as Hg22+ Figure 2.22 Common Cations Figure 2.22 Common Cations and Anions Compounds with Polyatomic Ions Compounds with Polyatomic Ions Polyatomic Ions contain covalently bonded atoms with an overall charge to make ion Can be Anion or Cation : NO3, SO42, NH4+ Polyatomic Ions Oxyanions Polyatomic Ions Oxyanions Oxyanions Contain O Two in series Lower #O ite: SO32 Sulfite Sulfate Higher #O ate: SO42 Lowest # O – Highest # O Four in series add hypo and per ClO Hypochlorite ClO2 Chlorite ClO3 Chlorate ClO4 Perchlorate Polyatomic Ions Oxyanions Polyatomic Ions Oxyanions Typical examples of Oxyanions Na2SO3 Sodium Sulfite K2SO4 Potassium Sulfate NaClO Sodium Hypochlorite AgClO4 Silver Perchlorate Hydrates Hydrates Sodium Sulfate decahydrate Often Molecules cocrystallize with water Indicate number of waters with Greek Prefixes mono, di, tri…deca etc. Table 2.6 Na2SO4∙10 H20 Binary Covalent Compounds Binary Covalent Compounds Type III Formed Between NonMetals Rules similar to naming Binary Ionic compounds Element with lower group number comes first e.g. CO – carbon monoxide Exception With O and Halogen the halogen comes first in name e.g. BrO= Bromine Oxide Elements within a group use element with higher period first in name e.g. ICl= Iodine Chloride Binary Covalent Compounds Binary Covalent Compounds Type III 1st element takes name of element 2nd element treated like anion root + ide Prefixes indicate numbers of atoms 1st group Di, tri, tetra (never mono) 2nd group Mono, di, tri, tetra etc. CO2 = Carbon Dioxide P2O5 = Diphosphorous Pentoxide Binary Covalent Compounds Binary Covalent Compounds Type III Note Contraction of Prefix with vowels P2O5 = Diphosphorous Pentoxide Mono + Oxide = monoxide Tetra + oxide = tetroxide Penta + oxide = pentoxide But Penta + Chloride = pentachloride Acids Acids When dissolved in water acids release free H+ Acids can be viewed as one or more H+ attached to an anion. Acids from halides are named as covalent cmpds The anion of an acid may or may not contain O HCl Hydrogen Chloride HF Hydrogen Fluoride Naming Acids Naming Acids Anions without Oxygen If we are dealing with pure substance use proper name When dissolved in water choose root of anion
Prefix Hydro Suffix –ic HCl – Hydrochloric Acid HCN – Hydrocyanic Acid HCl Hydrogen Chloride HCN Hydrogen Cyanide Naming Acids Naming Acids Anions with Oxygen If the anion name ends in ate change it to the root + ic If the anion name ends in ite change it to the root + ous Formula H2SO4 H3PO4 HC2H3O2 H2SO3 HNO2 Acids with Oxygen Acids with Oxygen
Sulfate Root + suffix Sulfuric Acid name
Sulfuric Acid Phosphoric Acid Acetic Acid Sulfurous Acid Nitrous Acid PO43
Acetate Phosphoric Acetic Sulfurous Nitrous Phosphate C2H3O2 SO32
Nitrite Acids Anions with Oxygen Acids Anions with Oxygen H2SO4 Higher O content use –ic Sulfuric acid H2SO3 – Lower O content use –ous Sulfurous acid HNO3 – Nitric Acid HNO2 – Nitrous Acid ...
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