HONORS CHEMISTRY Unit C: Chemical Bonding, Formulas, Reactions & Equations CHAPTER SIX: CHEMICAL BONDING

Transcription

1 HONORS CHEMISTRY Unit C: Chemical Bonding, Formulas, Reactions & Equations CHAPTER SIX: CHEMICAL BONDING

2 IONIC & COVALENT BONDS uchemical BONDS are formed from a mutual attraction between the nuclei and valence electrons of different atoms uthe force of attraction binds atoms/ions together uionic and COVALENT bonding are the two most general bonding types

3 BOND CHARACTER uionic BONDING results from the electrical attraction between cations and anions (IONS) ucovalent BONDING results from the sharing of electron pairs between atoms (ATOMS)

4 BOND CHARACTER

5 IONIC BONDING ubond types are almost never PURELY ionic or covalent ubond character is based on 100% scale ugreater than 50% ionic is IONIC uelectronegativity difference (END) greater than 1.7

6 COVALENT BONDING ubond types are almost never PURELY ionic or covalent ubond character is based on 100% scale ugreater than 50% covalent is COVALENT uelectronegativity difference (END) of 1.7 or less ( )

7 COVALENT BONDING ucovalent bonds can be classified as POLAR COVALENT or NON-POLAR COVALENT upolar COVALENT bonds are shared unevenly and have END values unon-polar COVALENT bonds are shared evenly and have END values

8 COVALENT BONDING & COMPOUNDS umolecules are groups of neutral atoms held together by covalent bonds umolecular COMPOUNDS are chemicals whose simplest unit is a molecule umolecular FORMULAS show the type and number of atoms combined in a single molecule

9 COVALENT BONDING & COMPOUNDS udiatomic MOLECULES are molecules containing only 2 atoms (usually the same element) umagnificent SEVEN: H 2, N 2, O 2, F 2, Cl 2, Br 2, I 2

10 COVALENT BOND FORMATION ucovalent bonds form because of the attractive forces between nuclei (+) and valence electrons (-) of two or more atoms uelectrons repel each other & nuclei repel each other uthe bond settles at the point where attraction and repulsion balance out (lowest PE)

11 COVALENT BOND FORMATION

12 COVALENT BOND CHARACTERISTICS ushared electron pairs uoverlap of valence electron orbitals uresults in a molecule with a decreased PE & increased stability

13 COVALENT BOND CHARACTERISTICS ubond ENERGY is the energy is required to break a covalent bond ubond LENGTH is the distance between bonded atoms ubond LENGTH & BOND ENERGY depend on the sizes and EN of the atoms and number of bonded electron pairs

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15 ELECTRON DOTS & LEWIS STRUCTURES uelectron DOT NOTATION uses dots to show the valence electrons for an atom ulewis STRUCTURES use element symbols, electron dots, and bond lines to show the structure of a molecule uthe OCTET RULE (rule of 8) is usually followed, but many exceptions exist

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17 RESONANCE STRUCTURES uresonance STRUCTURES are representations of molecules that have multiple possible structures uresonance is bonding in a molecule that can be correctly represented multiple ways udrawn as 2 or more structures, but the reality is a single hybrid udouble arrow indicates resonance

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19 IONIC BONDING uionic COMPOUNDS are composed of cations and anions uthe ions combine so that the sum of the charges is equal to zero umost exist as crystalline solids (salts) uform 3-D network of many, many ions in a lattice pattern uelectrons transferred, not shared

20 IONIC BONDING ua FORMULA UNIT is the simplest collection of ions for which an ionic compound formula can be written uexpressed using whole numbers in the most reduced form ucation is listed 1 st, Anion is listed 2 nd ucharges must sum to zero, but are not included in the formula unit

21 IONIC BONDING

22 IONIC BONDING uionic bonds minimized PE, resulting in an orderly arrangement of ions as CRYSTAL LATTICE uattraction exists between cations & anions, but repulsion exists between like charged ions

23 IONIC BONDING ulattice ENERGY describes the strength of an ionic bond uion sizes affect the number of surrounding ions and crystal structure uions of greater charge (2 +/-, 3 +/- ) have a greater attractive force

24 IONIC vs. MOLECULAR BONDING umolecular and ionic bonds are very strong uionic bonds have a stronger force of attraction among formula units umolecules bond less strongly between each other (intermolecular bonds) uionic compounds are generally solid, hard, brittle, and only conductive in an (aq) state

25 POLYATOMIC IONS upolyatomic IONS are a group of covalently bonded atoms with an overall charge uvery common in biology, chemistry, and industry u8 MUST KNOW POLYATOMIC IONS: (see board)

26 METALLIC BONDING umetallic BONDING results from the attraction between metal atoms and their delocalized electrons umetals have few valence electrons, and many vacant orbitals uthe overlap of vacant orbitals allows electrons to be mobile in a metal sample

27 METALLIC BONDING

28 METALLIC PROPERTIES umalleability is the ability of a substance to be hammered into thin sheets (Al, Au, Pb, Sn, etc.) uductility is the ability of a substance to be drawn into a wire (Cu, Al, Fe, Ag, Au, etc.)

29 METALLIC PROPERTIES umetals are CONDUCTIVE (heat & electricity) umetals can be polished to reflect light (LUSTER)

30 MOLECULAR GEOMETRY uproperties of molecules depend on the elements and the shape of the molecule ubond polarity and molecular polarity are important characteristics of molecules uthe shape can be predicted by the molecular formula and VSEPR Theory

31 VSEPR THEORY uvalence Shell Electron Pair Repulsion (VSEPR) uvsepr THEORY states that repulsion between sets of valence shell electron pairs around atoms causes the pairs to be oriented as far apart as possible uuses all 3-D space and focuses on the internal atom(s)

32 VSEPR THEORY

33 VSEPR THEORY ubonding PAIRS are the electrons involved in the covalent bonds unonbonding PAIRS are lone pairs that are unshared uboth electron pair types repel others and compete for space unonbonding PAIRS repel stronger than bonding pairs

34 HYBRIDIZATION uhybridization is the blending of the different energy s & p orbitals to produce hybrid orbitals of averaged and equal energy uevidence for HYBRIDIZATION is seen in the fact that all bonding regions around an atom appear uniform

35 HYBRIDIZATION

36 INTERMOLECULAR FORCES uintermolecular FORCES (IMF) are the forces of attraction between molecules uvary in strength, but generally weaker than covalent bonds (intramolecular within ) uimfs: Dipole-Dipole Interactions, Hydrogen Bonding, Dispersion Forces

37 INTERMOLECULAR FORCES

38 MOLECULAR POLARITY upolar MOLECULES have a strong IMF upolar molecules act as DIPOLES which are equal and opposite partial charges ubond POLARITY and MOLECULAR GEOMETRY determine molecular polarity umolecules are generally POLAR or NON-POLAR

39 MOLECULAR POLARITY

40 HYDROGEN BONDING uhydrogen BONDING is an IMF where an H atom bonded to an N, O, F atom in a molecule is attracted to the non-bonding electrons of an electronegative atom in a nearby molecule usmall size of H atoms and partial positive charge allows for hydrogen bonding urepresented by dotted lines

41 HYDROGEN BONDING

42 DISPERSION FORCES udispersion FORCES are the attractions that result form the constant motion of electrons ucreates instantaneous and weak dipoles uacts on all atoms and molecules including Noble Gases and Non-Polar Molecules udispersion FORCES are stronger for higher electron or mass atoms and molecules

43 DISPERSION FORCES