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Bonds Chemical Bonds Unit 3 Chemistry I. Elements and Periodic Table  Elements are organized into columns and rows  Columns have same number of valence.

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Presentation on theme: "Bonds Chemical Bonds Unit 3 Chemistry I. Elements and Periodic Table  Elements are organized into columns and rows  Columns have same number of valence."— Presentation transcript:

1 Bonds Chemical Bonds Unit 3 Chemistry I

2 Elements and Periodic Table  Elements are organized into columns and rows  Columns have same number of valence electrons (generally)  Rows for s and p are in the same energy level  Metals on left, nonmetals on right, metalloids are stair-step in p block. These divide metals and nonmetals

3 Element Classification  Metals  Solids at room temperature  Malleable and ductile  Good conductors  Nonmetals  Gases at room temperature (bromine is exception)  Brittle and dull  Poor conductors  Metalloids  Physical and chemical properties of metals and nonmetals

4 Nuclear Attraction  Shielding electrons  Electrons in the inner energy levels block the attraction from the nucleus to electrons in the outer energy level  Effective nuclear charge  Attraction between the nucleus and the electrons in the outer energy level

5 Periodic Trends  Atomic radius  Electronegativity  Ionization energy  Ionic radius

6 Bonding  Chemical Bonding  Bond is a force holding two atoms together  Type of bond is determined by the number of valence electrons

7 Ions  Ions  Charged particles from gaining or losing electrons  Done to reach a noble gas configuration (to be stable)  Number of electrons gained/lost depends on the number of valence electrons  Positive ions (cations) - metals  Atom loses one or more electrons  Transition metals can form more than one type of cation  Negative ions (anions) - nonmetals  Atom gains one or more electrons

8 Naming Ions  Cations keep their name and add the word ion  Anions change the suffix to --- -ide and add the word ion(oxide ion, chloride ion)

9 Ionic Bonds  Result from:  Metal cation losing one or more electrons  Nonmetal anion gaining one or more electrons  Opposite charges attracting one another  Naming  Cation is listed first (keeps its name)  Anion is listed second (has –ide suffix)

10 Polyatomic Ions  Ions made from more than one atom  Charge relates to the entire group of atoms  Indicates the number of electrons needed to gain or lose  List found on page 224.

11 Ionic Bonds and Metals  S Block metals have one oxidation number (number of electrons can lose)  D and P block metals can have more than one oxidation state  Must indicate the number of electrons lost with a Roman numeral in the name

12 Transition Metal Examples  Copper (II) chloride  Silver (I) sulfide  Lead (IV) oxide  Chromium (III) bromide  Vanadium (V) selenide

13 Metallic Bonds  Metals can exist bonded to other metal atoms  Sea of Electrons model proposes electrons travel through the metal atoms  Electrons changing atoms are called delocalized  Metallic properties are because of delocalized electrons (high MP/BP, good conductor, malleable)  Alloys are combinations of different metals

14 Covalent Bonds  Occur to achieve a noble gas configuration (8 valence electrons)  Electrons are shared between two nonmetals  More common than ionic bonds (N 2, H 2 O, CO 2 )

15 Types of Covalent Bonds  Single covalent bonds share one pair of electrons (one electron from each atom)  Double covalent bonds share two pairs of electrons  Triple covalent bonds share three pairs of electrons

16 Bond Strength  The longer the covalent bond, the weaker the bond is  The shorter the covalent bond, the stronger the bond is  Triple bonds are the strongest; single bonds are the weakest

17 Covalent Naming  Binary covalent molecules  First element  Keeps its name  Uses a prefix except if only one atom  Second element  Suffix is –ide  ALWAYS uses a prefix

18 Lewis Structures  Method used to predict the shape of molecules  Dots represent valence electrons and a dash/line represent a covalent bond  Hydrogen is always an end atom  Atom with least attraction for shared electrons is often the central atom (Usually furthest left)  Start on left of formula and work to right

19 VSEPR Model  Molecular shape can be determined based the Lewis structure of a molecule  Shape will determine many of the physical and chemical characteristics of a molecule  VSEPR (Valence Shell Electron Pair Repulsion) is the model  Arrangement is based on minimizing repulsion around a central atom  Lone pairs repel more than bonded pairs  Different shapes have different angles/properties  See page 260

20 Electronegativity and Polarity  Types of bonds are determined through difference in electronegativity (EN)  Difference in EN greater than 1.7 is an ionic bond  Difference in EN between 0.3 and 1.7 is a polar covalent bond  Electrons tend to be in the orbital of the element with higher electronegativity (partial negative)  Difference in EN less than 0.3 is a nonpolar covalent bond  Electrons are shared evenly (no partial charges)

21 Polarity  Bonds vs. Molecules  Bonds are based on electronegativity differences  Molecules have polarity based on geometry  All polar bonds can be nonpolar molecule

22 Intermolecular Forces (IMF)  Attraction between two molecules  Strength of IMF helps determine the phase of matter of a substance  London dispersion forces (dispersion forces)  Between nonpolar molecules  Weakest of IMFs  Dipole – dipole forces  Between polar molecules  1% as strong as a covalent bond  Hydrogen bonding (strongest IMF)  Specific dipole-dipole force between H and N, O, or F

23 Properties of Ionic Compounds  Ionic compounds form a crystal lattice  Crystal lattice is a highly ordered three dimensional shape  Positive ions are surrounded by negative ions and negative ions are surrounded by positive ions  Lattice energy is the energy needed to separate one mole of ions  The more negative the lattice energy, the stronger the attraction  Values are negative because energy is released when broken (exothermic)

24 Properties of Ionic Compounds  Due to strong attractions between positive and negative ions  High melting points and boiling points  Can conduct electricity in a liquid state (or aqueous state)  Hard and brittle

25 Properties of Covalent Molecules  Crystal lattice structure with complete molecules at the points  Low melting points and boiling points  Can be hard/soft, flexible  Nonpolar molecules will not conduct electricity

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