2Daily AssignmentExplain, using your periodic table, how to calculate (find) the following in an atom:Atomic number _____________________Atomic mass _______________________Identity of the atom _________________Number of protons __________________Number of neutrons __________________Number of electrons ________________
3The Purpose of an Element Remember that the desire of every element is to be “happy,” that is, to have a full valence shell.Atoms are willing to do whatever it takes to accomplish this, including align themselves with some “seedy” atomsHaving a full valence shell is also known as having a stable electron configuration
4Drawing ElementsIn order to talk about bonding, we need to be able to visualize the elements we’re talking about. Here’s how we do that:
5Ionic Bonding Na gives an electron to Cl, creating two ions. atom atom When atoms bond together to form compounds, they may gain or lose electrons. An atom that has gained or lost electrons is called an ION.Na gives an electron to Cl, creating two ions.atomatom
6Let’s Look Closer… The atom Na has 11 (-) electrons, balanced by 11 (+) protons in the nucleus.The atom Cl has 17 (-) electrons, balanced by 17 (+) protons in its nucleus.
7THE OCTET RULEThe octet rule says that atoms tend to gain, lose or share electrons so as to have eight electrons in their outer electron shell (HAPPY).Na atom Cl atomNa has1 e Cl has 7e-( it can lose one or gain seven) (it can lose seven or gain one)If Na gives up its electron to Cl, both will have 8e- .
8IONS are formedWhen a bond is formed, Na gives up one electron to Cl, reducing its number of electrons to 16 and increasing Cl’s electrons to 18.Na forms a 1+ charge, since it now has one more proton than electron. Cl forms a 1- charge, since it now has one more electron than proton.The charge is written as a superscript number to the right of the element’s symbol.
9What is the charge? Mg loses two electrons to form ______________ Oxygen gains two electrons to form __________Phosphorus gains three electrons to form _______Carbon gains four electrons to form _________Calcium loses two electrons to form __________How was N3- formed? ___________________How was Ag1+formed? ___________________
10Daily AssignmentWhy do most atoms tend to form compounds, as opposed to existing in their unbonded state?
11The Structure of an IonTo find the number of protons, neutrons, and electrons in an ion, you need to look at the atomic number, mass, and the charge on the ion. Remember, atomic number = # of protons atomic mass = protons + neutrons neutrons = atomic mass – atomic number Now, to calculate the number of negative electrons, you must balance the charge of the ions with the number of positive protons.
12Periodic Table Atomic number = ______ Atomic mass = _______ Charge = ___________Element name _______Element symbol _______# protons __26___# neutrons __30__# electrons ___23__Atomic number = __26__Atomic mass = _______Charge = ___________Element name _______Element symbol _______# protons _____# neutrons __29__# electrons __24___
13Periodic Table Atomic number = __26__ Atomic mass = __56___ Charge = ___+3_____Element name __IronElement symbol __Fe___# protons __26___# neutrons __30__# electrons ___23__Atomic number = __26__Atomic mass = __55___Charge = ___+2____Element name __Iron__Element symbol __Fe___# protons __26_# neutrons __29__# electrons __24___
14Periodic Table Atomic number = __16__ Atomic mass = _______ Charge = _____2-____Element name ______Element symbol ____# protons ______# neutrons __18__# electrons _____Atomic number = _____Atomic mass = ___7____Charge = ___________Element name _______Element symbol _______# protons __3___# neutrons _____# electrons ___2__
15Periodic Table Atomic number = __16__ Atomic mass = __34__ Charge = _____2-____Element name ___Sulfur_Element symbol __S___# protons __16___# neutrons __18__# electrons __18___Atomic number = __3___Atomic mass = ___7____Charge = ____+1____Element name __Lithium_____Element symbol __Li___# protons __3___# neutrons __4__# electrons ___2__
16Periodic Table Atomic number = ______ Atomic mass = __40__ Charge = _____1+____Element name _______Element symbol ___K___# protons _____# neutrons ____# electrons _____Atomic number = __19__Atomic mass = _______Charge = ___________Element name _______Element symbol _______# protons _____# neutrons __22__# electrons __19___
17Periodic Table Atomic number = __19__ Atomic mass = __40__ Charge = _____1+____Element name __Potassium___Element symbol ___K___# protons __19__# neutrons __21_# electrons __18__Atomic number = __19__Atomic mass = ___41____Charge = _____0______Element name ___Potassium____Element symbol ___K___# protons ___19__# neutrons __22__# electrons __19___
18Review Time!!Explain the “Octet Rule” _______________________________________ _______________________________________ _______________________________________ ________One atom has 2 electrons in its outer shell. Another atom has six. Will they combine to form a compound?What about an atom with two electrons and 2 atoms with seven outer shell electrons?
19Why do atoms combine?Atoms will combine with other atoms to achieve a chemically stable arrangement of their electrons.Recall, the OCTET RULE drives chemical bonding. A chemically stable arrangement of electrons is attainable by completely filling the outer shell (with eight electrons*).
20To share or to not to share? Atoms, like small children, will always do what benefits them most In this case, their electrons can either be shared between atoms or transferred from one atom to another to form a chemical bond.
21Ionic BondIonic Bonds occur when one atom loses electrons to another atom that gains them. Ions arrange themselves into crystal lattices.
22Ionic Bonds = transfer of electrons between atoms in a reaction * Only outer shell electrons shown *
23Writing Ionic Compounds To write the newly formed ionic compound, take the charges after the reaction, criss-cross them, and drop the sign.NaCl MgS KI
24Daily AssignmentDraw a dot diagram and complete the charges for the reaction of:Sodium Boronate
25Molecular (Covalent Bond) Electrons are “shared” between atoms. Since they spend time in the electron clouds of each atom, the atom “feels” complete and happy.
26The fluorine atoms, being nice to each other as they are, decide to share two electrons - one from each of them. This obviously means that one of the atoms - the one donating - has a complete outer shell; the other atom has a gap for two electrons, e.g. something with six electrons in its outer shell).Despite the fact that each atom has its own electron cloud, each atom also feels like it has a full outer shell because of the shared electrons.All electrons are still spinning around each atom, but because of the sharing, the atoms are bonded together in order to maintain the sense of a full outer shell.
27Molecular (Covalent) Bond Most atoms become chemically stable by sharing electrons. This does not result in the formation of ions (the atoms do not have charges).These electrons belong to both H and O. At any point in time they can exist in either electron cloud.
28Daily AssignmentDo the following reactions at your seat. Draw the dot diagram. Are they covalent or ionic bonds?Hydrogen and HydrogenChlorine and ChlorineHydrogen and Chlorine
29Daily AssignmentCopy the reactions listed above. Determine the type of chemical bond formed during the reactions.
30Multiple Covalent Bonds Sometimes elements do not combine with other elements. Instead, atoms of the same element combine. When this happens, we write it a special way. Take Nitrogen, for example.Single bondDouble BondTriple Bond
31Unequal Electron Sharing Those elements on the right of the periodic table crave electrons more than others, and those at the top crave them more than those at the bottom.
32Polar Covalent BondsOccurs when atoms get greedy and “hog” the shared elements.Example: Water
33Polar and Nonpolar Molecules Not all molecules that contain polar bonds are polar molecules. It depends on how the electrons are shared.Water is a polar molecule because the oxygen has more need for the electrons.Carbon Dioxide shares the electrons between the carbon and oxygen atoms
34Polar and Nonpolar Molecules The attractive forces between polar molecules are greater than those in non polar molecules.The positive and negative ends of a polar molecule are attracted to eachother and create bonding forces.Water is an example
35Writing Chemical Formulas A chemical formula is a combination of element symbols and subscript numbers that is used to show the composition of a compound.MgCl2 The formula above tells you that the compound magnesium chloride contains one atom of magnesium bonded to two atoms of chlorine. There are three total atoms in the compound.
36Counting Atoms in a Chemical formula List the name of each element, the number of atoms of that element, and the total number of atoms in the chemical formula.H2O MgF NH4I
37Parentheses in a chemical formula Parentheses are used around polyatomic ions in a chemical formula. The subscript number to the right of the parentheses is used as a multiplier for the atoms inside.Ba(OH) (NH4)2S Au2(CO3)2
38Coefficients in a Chemical formula Coefficients are used in a chemical formula to represent the number of units of the compound present. They act as a multiplier for all atoms present in the formula.3 H2 O Ba3(PO4)2
39Counting Atoms in a formulas List the number of atoms of each element and the total number of atoms in the compound for the formulas listed below.2 C4H (NH4 )2CO Al2(SO4 )3
40Daily AssignmentYou have learned that elements chemically bond together (ionic or covalent) to form new substances.You have learned that a chemical formula indicates the number of atoms of each element contained in a chemical compound.magnesium chlorideMgCl2Write a formula for a compound with two aluminum and three sulfur atoms. Write a formula for a compound with one beryllium and two iodine atoms.
41Ionic Compounds calcium fluoride Ionic compounds are formed from the transfer of electrons, resulting in the creation of a positive ion and a negative ion.The compound is always written positive ion (cation) then negative ion (anion).The negative ion (if it is an element) will have an –ide ending.calcium fluoride
42Metal CationsSome metals form multiple ions. Alkalis, Alkaline Earths, and Aluminum form ions with positive charges equal to their group number, such as K+, Ca2+, and Al3+Many transition metals form more than one type of ion. Examples include copper I and copper II. Roman numerals designate the charge.Cu2O CuO
43Polyatomic Ions Ammonium NH4+ Acetate C2H3O2- Compounds that join together in a regular way and act as one unit. It can have either a negative or positive charge.Some examples of polyatomic ions:Ammonium NH4+ Acetate C2H3O2-Hydroxide OH- Peroxide O22-Nitrate NO3- Hydrogen SulfateSulfate SO HSO4-Carbonate CO32- Hydrogen CarbonatePhosphate PO HCO3-Chromate CrO42- Hydrogen PhosphateSilicate SiO32- HPO42-Permanganate MnO4- Hypochlorate OCl-
44Writing Compounds Write the symbol for the positive and negative ions. List the oxidation number (charge) for each. This can be found on your periodic table or listed in the formula name, following the positive ion as a roman numeral.Find the oxidation numbers for the following ions:Ag Au (I) Pb (IV) SBe Pb (II) Al CaH Cl O F
45Criss- cross and drop the charge! Writing CompoundsBalance the charges by the criss-cross method.Criss- cross and drop the charge!Place all parentheses around all polyatomic ions. Make sure the criss-crossed number is placed outside the parentheses.Reduce subscript numbers to reflect the Least Common Multiple.
46LETS TRY MORE Sodium nitride Magnesium bromide Barium sulfide Lead (IV) oxidePotassium selenide Chromium nitride Copper (I) oxide Copper (II) oxide
47Daily Assignment Write the formula for barium chloride. Explain, using electron dot diagrams, how this compound forms and whether it will be an ionic or covalent bond formed. (I’ll start you off)Ba + Cl + Cl
48Writing ionic formulas with polyatomic ions Place all parentheses around all polyatomic ions. Make sure the criss-crossed number is placed outside the parentheses.Reduce only the subscript numbers to the outside of the parentheses.Lead (II) phosphate magnesium acetateAmmonium sulfide silver silicate
50More practice with polyatomic ions Take out your homework and periodic table. Mercury (II) carbonate Platinum (I) sulfidePlatinum (IV) sulfate ammonium nitrateCalcium iodide hydrogen peroxide
51Writing formulas of Molecular Compounds As you recall, elements undergoing molecular (covalent) bonding are sharing electrons, so no charges (or ions) are formed during the formation of the compound.Molecular compounds are named and written using a system of Greek Prefixes, which must be memorized.
52Greek Prefixes – Molecular Compounds One = mono Six = hexaTwo = di Seven = heptaThree = tri Eight = octaFour = tetra Nine = nonaFive = penta Ten = deca
53Writing formulas of Molecular Compounds Just let the prefix for the element in the formula become the subscript number for that element. If there is no prefix, the subscript is 1.Examples:dihydrogen monoxide trisilicon pentabromidetetraphosphorus hexasulfide carbon dioxidearsenic trichloride decaphosphorus heptoxide
54Quiz Chapter Six 1. disulfur hexoxide 2. ammonium sulfide iron (III) carbonateiron (II) carbonatealuminum phosphitegold (III) nitridediphosphorus pentabromidesilicon sulfidetetraradon heptafluoridepotassium oxide
55Naming Ionic Formulas Write the name of the first element Add charges to periodic table Write the name of the first elementWrite the name of the second element changing the name to an _ide ending.Reverse cris-cross the subscript numbers to determine the charge of both ions.
56Naming Ionic FormulasCheck the periodic table to determine the number of positive charges that the first element forms. If it only forms one, and it is the one listed, then you are doneIf it only forms one, but it is not the one listed, then it has been reduced. Determine the multiplier and multiply both charges to determine the correct charge formed.If it forms more than one, write the Roman numeral equivalent of that charge in the compound’s name.If it forms more than one, yet none are listed, it has been reduced. See above, and use the Roman numeral.
59Naming Ionic Formulas with Polyatomic Ions Follow all of the same rules, with the following exceptions:Never change the name of a polyatomic ionPlace parentheses around polyatomic ions before reverse criss- crossing (if they are not already there)Check the charges of element and polyatomic ions to check for a reduction.
60Let’s try some Au2(CO3)3FeSO4Ca3(PO4 )2 (NH4)2CrO4
61I love naming formulas Ba(C2H3O2)2Pt(NO3)4Ni2 (SiO3)3 HgSO3
62Naming Molecular formulas Simply let the subscript number become the prefix for the element’s name.The first element keeps its name. It only gets a prefix if it has a subscript in the formulaThe second element always gets an – ide suffix (ending). The second element always gets a prefix.N20 P2O5 S3Cl CO
63Metallic BondsMetals have special bonds because of the way they configureMetals form regular patterns and share electrons with all the atoms around it, effectively forming cationsThis forms a crystalline lattice like those in polar bondsThe metal is effectively neutral, though.
64Metallic Bonds Properties of Metals explained Conductivity Metals are good conductors of electricity, but why?The lattice structure of metal atoms allows electrons to flow freely through the metalMalleabilityA block of ice, if hit with a hammer, would shatter because of its ionic bondsAlthough strong, the lattice in a metal is not as rigid as the lattice in ionic bonds. This allows the atoms to move but not break because the electrons keep the metal anions in place
65AlloysAn alloy is a mixture of metals to give it more desirable properties, such as hardness or resistance to rustCopper AlloysFirst alloy was Bronze – a mixture of copper and tinBrass – another alloy of copper, formed by mixing copper and zinc
66Alloys Iron Alloys The best known iron alloy is steel Steel is a combination of iron and carbon, which hardens the iron.Stainless steel contains about 10% of chromium, which makes it shiny and resistant to rustingOther elements, such as phosphorus, manganese, sulfur, and silicon, are added to steel to make strong, flexible metals used in bridges
67AlloysAluminum alloys are used in making airplane sheet metal (mixed with copper or manganese)Aluminum is also mixed with magnesium to create a lightweight, but strong metal (sometimes used in performance bicycle frames)