2What we will LearnRelate chemical behavior of an element, including bonding, to its placement on the periodic tableExplain how elements form chemical bonds and identify the role of electrons in bondingPredict chemical formulas of compounds made up of two different elementsWrite chemical formulas for compounds made up of many different elementsCalculate the formula mass of a compound and compare different compounds based on their formula masses
3The Octet RuleWhen an atom has eight valence electrons, it is said to have an octet of electrons.Atoms form chemical bonds with other atoms by either sharing electrons, or transferring them in order to complete their octet and move to a lower energy state.This is known as the octet rule.
4Predicting Atomic Behavior Looses 1 electron to satisfy Octet RuleLooses 1 electron to satisfy Octet RuleOctet Rule Satisfied
5Types of BondsChemical Bonds fall into two categories, depending on whether the valence electrons are transferred or sharedIonic Bonds: When electron(s) are transferred from one atom to the other.Covalent Bonds: When electron(s) are shared between atoms.
6Ionic BondsAtoms that either gain or lose an electron become ions. Ions may have either positive or negative electric charge.The positive and negative ions are attracted to each other, creating the bond. Ionic bonds tend to form between more than one pair of atoms at a time. The bond between sodium (Na) and chlorine (Cl) in sodium chloride (salt) is a good example of an ionic bond.
7Ionic BondsAlkali MetalsIf you put an alkali (Na) with a halogen (Cl), you get an ionic bond because one atom strongly wants to lose an electron and the other strongly wants to gain one.Halogens
8Ionic BondsWhen sodium, with its +1 charge, comes into contact with chlorine, with its -1 charge, they become electrically neutral as longas they are together. This is because +1 and -1 cancel each other out.This also explains why sodium and chlorine combine in a 1:1 ratio to make sodium chloride
9IONIC BONDING PROPERTIES OF IONIC COMPOUNDS Form between a metal and a nonmetalBrittle/crystallineHigh melting/boiling pointsDissolve (ions come apart) in water
10IONIC BONDING NAMING IONIC COMPOUNDS The metal (positive ion) goes first in the formulaThe nonmetal (negative ion) goes last in the formulaThe name of the metal stays the same, and the name of the nonmetal is changed so it endsin –ide.For example: Oxygen becomes Oxide
11NAMING IONIC COMPOUNDS NaClHFMgI2KBrSodium ChlorideHydrogen FluorideMagnesium IodidePotassium BromideThis is called Binary Nomenclature
12Oxidation NumbersA sodium atom always ionizes to become Na+ (a charge of +1) when it combineswith other atoms to make a compound. Therefore, we say that sodium has anoxidation number of 1+. An oxidation number indicates how many electrons arelost, gained, or shared when bonding occurs.
14Writing a Chemical Formula Using Oxidation Numbers Find the oxidation numbers of each element in the compound2. Determine the ratios of each element and then write the chemical formula
15Oxidation Numbers Element Oxidation Number Copper (I) 1+ Copper (II) 2+Iron (II)Iron (III)3+Chromium (II)Chromium (III)Chromium (VI)6+Lead (II)Lead (IV)4+Some elements have more than one oxidation number. In this case, roman numerals are used to distinguish the oxidation number.
16Polyatomic IonsPolyatomic Ions: contains more than one type of atom (poly means many)NameFormulaOxidation #AmmoniumNH4+1+AcetateC2H3O2-1-HydroxideOH-PhosphatePO43-3-NitrateNO3-HydroniumH3O+SulfateSO42-2-
17Writing Chemical formulas with polyatomic Ions 1. Find the formula and charge of the positive Ion2. Find the formula and charge of the negative ion (for poly atomic ions you will not have to memorize them they will be given)3. Determine how many of each ion are needed so the charges are equal to zero and write the chemical formula (Hint: Least common multiple)Example: Al2(SO4)3
18Writing Chemical formulas with polyatomic Ions Example: Write the formula for Aluminum SulfateAl SO42-1. Find Aluminum’s Oxidation Number (it is 3+)3. How many of each do we need to satisfy the charges? The common denominator between 3 and 2 is 6.6/3 = 2 Aluminums6/2 = 3 Sulfates2. Sulfate’s oxidation number will be given (it is 2-)Al2(SO4)3
19Covalent BondsIn a covalent bond the electrons are shared between atoms.An important differencebetween covalent and ionic bonds is that covalent bonds act only between the atoms in a single molecule, while ionic bonds act between all adjacent atoms
20Covalent BondsElements that have two to six valence electrons tend to form covalent bonds with each other since the tendency to take or receive electrons is more matched.Covalent bonds can form between two different types of atoms, or between two or more atoms of the same type. The gases nitrogen (N2), oxygen (O2) and hydrogen (H2) are a few examples. We call these covalently bonded atoms of the same type diatomic molecules.
21Covalent Bonds This is how you DRAW a SINGLE COVALENT BOND A single line means each atom shared one electron each to get full.
22Covalent BondsSome atoms need more than one electron to become stable.What type of element is oxygen?What kind of bond will two oxygen atoms make?
23Covalent Bonds Draw the Electron Dot Diagram for Oxygen. How many electrons does each oxygen need to become stable?How many TOTAL electrons are shared?FOUR
24O Covalent Bonds How would you draw this? This is a DOUBLE COVALENT BOND.2 pairs of electrons are sharedO
25Covalent Bonds How many total electrons are shared? What kind of bond would 2 nitrogen atoms form?COVALENTHow many electrons does each atom need?ThreeHow many total electrons are shared?Six, 3 pairs of electrons
26Covalent Bonds How would you draw this? This is a TRIPLE COVALENT BOND 3 pairs shared
27Covalent BondsSometimes, one atom is not enough to fill all the “empty” spots another atom has.How many electrons does Carbon need to be stable?How many electrons does Hydrogen need to be stable?
28How do you write the Chemical Formula Covalent BondsHow do you write the Chemical Formulafor a MOLECULE?O2CH4H2F2N2
29Covalent Bonds Naming Covalent Molecules The element with the lowest ionization energy goes first (farthest from Fluorine).Each element gets a prefix to identify how many there are.Exception: If there is only one of the first element, no prefix is used.The second element changes so that it ends with –ide.
30Covalent Bonds Prefixes for covalent bonding nomenclature Number 1Mono-5Penta-2Di-6Hexa-3Tri-7Septa-4Tetra-8Octa-
31Name the following molecules Covalent BondsName the following moleculesH2OCO2SF6B2SiSO3P2O5Dihydrogen monoxideCarbon dioxideSulfur hexafluorideDiboron monosilicideSulfur trioxideDiphosphorus pentoxide
33Molecular WeightDoes a molecule of water (H2O) have the same mass as a group of atoms (also called a formula unit) that make up the ionic compound calcium carbonate (CaCO3)?
34Molecular WeightCarbon atoms are used as a standard for determining the atomic mass units for theother elements on the periodic table. One carbon atom is equivalent to atomic mass units.
35Molecular Weight A chemical Formula does 3 things for us: 1. Tells us the types of atoms in the compound2. Lets you know if polyatomic ions are present3. Allows you to calculate the Molecular Weight (MW) or Formula Mass
36Molecular Weight So one molecule of water has: Lets go back to our first example: Water vs Calcium Carbonate.Water has a chemical formula of H2OHydrogen has an atomic mass of 1.01 amuOxygen has an atomic mass of amuSo one molecule of water has:2(1.01 amu) + 1(16.00 amu) = amu
37Molecular Weight So one molecule of Calcium Carbonate has: Lets go back to our first example: Water vs Calcium Carbonate.Calcium Carbonate has a chemicalFormula Of CaCO3Calcium has an atomic mass of amuOxygen has an atomic mass of amuCarbon has an atomic mass of amuSo one molecule of Calcium Carbonate has:1(40.08 amu) + 1(12.01 amu) + 3(16.00 amu) = amu
38Molecular Weight The molecular weight comparison: 18.02 amu for Water vs amu for Calcium Carbonate
40Molecular Weight Rules for finding Molecular Weight: 1. Write the chemical formula for the compound.2. List the atoms, number of each atom, and the atomic mass of each atom3. Add up the values for each type of atom
41IsomersIsomers: Compounds that have the same molecular formula but different structural formulas.
42IsomersExample: C3H6OHow many ways can we bond these atoms? (hint there are 7 ways minimum)