Atoms and Bonding

Chapter 4Unit Introduction to the chemistryPhysical ScienceMrs. N. CastroAtoms and Bonding1HomeworkWork chapters vocabulary words in your home.Remember, as always, do it in the index cards. Front part the vocabulary word. Back part vocabulary word definition.Bring all the index card with a rubber band for tomorrow. Value 10 points.

All the vocabulary words.2Atoms, bonding and the Periodic TableRead pages 125 to 127.Answer the following:What is compound?How the elements are combined?What is chemical bond?Which particle from the atom can form chemical bond?Compound Substance made of two or more elements chemically combined in a specific ratio or proportion. The elements are combined using a chemical bond.Chemical bond force of attraction that holds atoms together as a result of the rearrangement of the electrons between them.Electrons

3Atoms, bonding and the Periodic TableIs there all electrons in the same energy levels?Which electrons can form chemical bond, all of them or any specific?In which energy level we can find the valence electrons?What determines the valence electrons in each atoms?No

Valence electrons

In the higher energy level with the higher amount of energy.They determines the chemical property, to whom the atom will establish a chemical bond and how will be.4Atoms, bonding and the Periodic TableGroup or Family numberValence electronsChemical bond111222133314441553166217711880Which is the maximum of chemical bonds that the atom can do?Which family is able to perform the maximum chemical bond?Which is the minimum?

Note: Families 3 to 12 will be study in future grades.5Atoms, bonding and the Periodic TableHow the valence electrons can help me to determines the quantity of chemical bonds the atom can perform?Using the electron dot diagram or Lewis diagram.To perform electron dot diagram:Write the element symbol.Surround the symbol by dots.Each dot mean one valence electron.Maximum numbers of dots 8Maximum dots per side 2Side - 4 6Atoms, bonding and the Periodic TableAtoms tend to be more stable if they have 8 valence electrons. The only column in the Periodic Table with 8 valence electrons is family # 18. They are the most stable elements in the Periodic Table. This is the reason to explain why they dont perform chemical bond with any element.Family # 18 is nonreactive or stable.He (Helium) is an exception, because it has only 2 valence electrons and it stable or non reactive element. It is part of the Family 18.Another exception is H (Hydrogen), need only two valence electron to be stable. Actually, it has only one valence electron. Need only one more to complete it stability or nonreactive state.7Atoms, bonding and the Periodic TableLets work withElectron Dot Diagram.Teacher will perform someand you will perform more.8Atoms, bonding and the Periodic TableWays to forms atoms bonds:Valence electrons may be transferred from one atom to another. One atom loose the valence electron and the other gain it. Atoms share valence electrons.Depend on how the atom form the bond, it will be the chemical bond.Types of chemical bonds;Ionic bonds metal with nonmetalCovalent bonds nonmetal with nonmetalMetallic bonds metal with metal 9Atoms, bonding and the Periodic TableMetalReact by loosing valence electrons.Reactivity will depend on how easily its atoms loose valence electrons.NonmetalsReact when they gain or share enough electrons to have 8 valence electrons (except H).Nonmetals usually combine with metals by gaining electrons.Nonmetals can also combine with other nonmetals and metalloids by sharing electrons.10Atoms, bonding and the Periodic TableMetalloidsCan either lose or share electrons when they combine with other elements.HydrogenIts has 1 valence electron Family 1Is nonmetal.Properties very different from alkali metals.Share its electron when form compound with other nonmetals to obtain a stable arrangement of 2 electrons. 11Atoms, bonding and the Periodic TableN Element name?Find the protons, electrons and neutrons.Is N reactive or stable?Mention two elements with properties similar to N. Explain why they are similar.How many bonds N can performed?With which elements, N will prefer to establish chemical bond? Why?Practice12Atoms, bonding and the Periodic TableMore practicePerform all exercisesfrom your book,pages 125 to 129.Include Assess Your Understanding

13Ionic BondsLesson 2Pages 131 to 13714Ionic BondsTo perform ionic bonds you need ionsION is an atom or group of atoms that has an electric charge.Example: Cl-, Na+Types of ions:Negative ion when atom gain an electron.Positive ion when atom lose an electron.Examples:K = 1 valence electron, Family 1, lose the electron = K+Br = 7 valence electrons, Family 17, gain 1 = Br _

Metals atoms are likely to lose electrons.Nonmetals atoms likely to gain electrons.MetalNonmetal15Ionic BondsCommon IonsMonoatomic ion made of one elementExample: K+Polyatomic ions made of more than one elements. Can be positive or negative charges.Example: HCO3- = one Hydrogen, one Carbon and three Oxygen = one negative chargeSee table on page 132. 16Ionic BondsIonic bond is the attraction between two oppositely charged ions.Ionic compound resulting compound from ionic bond. The ionic compound always is neutral, charge = 0. The total positive charge of all positive ions equals to total negative charge of all the negative ions. Let see some examplesof ionic bonds.17Ionic Bonds Video

18Ionic Bonds FormulasWhat is the different between this? K , KBr , K+ , Br-K = element symbol KBr = chemical formulaK+ = positive ion Br- = negative ion

Chemical formula - is a group of symbols that show the ratio of elements in a compound.KBr ratio = one K and one BrMgCl2 ratio = one Mg and two Cl The formula tell you:The elements that component the compound.The ratio of each element in the compound (subscripts).

19Ionic Bonds FormulasRules:To write the formula for compound, always write the positive charge first and then the negative charge.Add subscripts that are needed to balance the charge. ONLY SUBSCRIPTS.If no subscripts is written, its is understood that the subscript is 1. Example: NaCl = no subscripts for both elements; means: one Na and one Cl.Formulas for compounds off polyatomic ions are written in a similar way.20Ionic Bonds NamesRules for ionic compounds:The name of the positive charge comes first, followed by the name of the negative ion.NaCl Sodium chlorideMgBr Magnesium bromideThe name of the positive ion is usually the name of a metal.If the positive charge is a polyatomic ion, use the name of the polyatomic ion. NH4Br Ammonium chlorideIf the negative ion is a single element, the end of its name changes to ide. MgO Magnesium oxideIf the negative ion is polyatomic, its name usually ends in ate or ite.NH4NO3 Ammonium nitrate.NH4HCO3 Ammonium bicarbonate21Ionic BondsExercises:Teacher exercises Find the ratio of each element in the compound.Write chemical formula for ionic's compounds.Name ionic's compounds.Complete exercises from pages 131 to 135.22Ionic BondsProperties of ionic compounds:Hard.Brittle crystals.Forms solids by building up repeating patterns of ions. This three dimensional arrangement is called crystals.High melting pointsWhen dissolved in water or melted, they conduct electric current.Attraction between ions is very strong, so it takes a lot of energy to break the bond.When ionic compounds dissolve in water, they become ions again.The charged particles carry electric current where the neutral ionic crystals do not.23Ionic BondsExtra exercises:A fluorine (F) ion has a charge of 1-. An aluminum (Al) ion has a charge of 3+.Draw for both atom the electron dot diagram.Explain how the F and Al would exchange valence electrons to form an ionic compound. Draw the explanation first and then explain in your own words.Write the compounds chemical formula.Name the compound.A potassium ion has a charge of 1+. A sulfide ion has a charge of 2-. What is the chemical formula for ionic compound and the name.Name the following compound MgOPerform exercises on pages 136 and 137.24Covalent BondsLesson 3Pages 138 to 14525Covalent BondsIt formed when 2 atoms share electrons.Usually are between nonmetals atoms.The attractions between the shared electrons and the protons in the nucleus of each atom hold the atom together in a covalent bond.The product of a covalent bond is called a molecule.A molecule is a neutral group of atoms joined by covalent bonds.

26Covalent Bonds

27Covalent BondsExercise:Draw the Lewis diagram for Bromine atom.Draw the Lewis diagram for the Br2 molecule. Perform exercise on page 139.28Covalent BondsAtoms can form single, double and triple covalent bonds by sharing one or more pairs of electrons.Double bond 2 atoms share 2 pairs of electrons

29Covalent BondsTriple bond share 3 pairs of electrons.

30Covalent BondsIdentify the single, double and triple covalent bonds:

Draw the Lewis diagram for (CH3)2SO - dimethyl sulfoxide

31Covalent BondsSolutionCHSO

Fam. 14Fam.1Fam.16Fam.16

32Covalent BondsProperties:Do not conduct electric current when melted or dissolved in water.Lower melting point and boiling point.33Covalent BondsSometimes, atoms of some elements pull more strongly on the shared electrons of a covalent bond than do atoms of other elements. As a result, the electrons ser shared unequally.Unequal sharing of electrons causes covalently bonded atoms to have slight electric charges.

34Covalent BondsTypes of covalent bonds:Non polar bond a covalent bond in which electrons are shared equally.Example: H2

35Covalent BondsPolar bonds Covalent bonds in which electrons are share unequally. When electrons in a covalent bond are shared unequally, the atom with the stronger pull gains a slightly negative charge. The atom with the weaker pull gains a slightly positive charge. Example: HF

36Covalent Bonds video

37Bonding in MetalsLesson 4Pages 146 -15138Bonding in metalsMetal atoms lose electrons easily because they do not hold their valence electrons very strongly.The loosely held valence electrons in metal atoms result in a type of bonding that happens in metals.Most metals are crystalline solids.A metal crystal is composed of closely packed, positively charged ions.Each metal ion is held in the crystal by a metallic bonds.Metallic bonds is an attraction between a positive metal ion and electrons surrounding it.

39Bonding in metalsMetallic bonds is formed an attraction within metal atoms.Video ...\..\Clark-9805.Fig.4 (2).movProperties:Luster When the light strikes these valence electrons, they absorb the light and then re-emit the light.Malleability and Ductility The positive metal ions are attracted to the loose electrons all around them rather than to other metal ions. These ions can be made to change position. However, the metallic bonds between the ion and the surrounding electrons keep the metal ions from breaking apart from one another.

40Bonding in metalsThermal conductivity Metals conduct heat easily because the valence electrons within a metal are free to move.Electrical conductivity Metals conduct electric current easily because the valence electrons in a metal can move freely among the atoms.

Alloys is a mixture made of two or more elements, at least one of which is a metal.Generally are stronger and less reactive than the pure metals from which they are made.Example: stainless steel = iron +carbon + nickel + chromiumGold jewelry = gold+ cooper + silver41Assess your understandingAll bondings42All Bondingshttp://www.bsc2.ehb-schweiz2.ch/Chemie/Simulationen%20Chemie/Bindung/Bindung%20Hundeanalogie.htm

Compare and contrast the following concepts:

Ionic bondCovalent bondMetallic Bond1.2.3.4.1.2.3.4.1.2.3.4.43END

Complete chapter review44