Ch.9 Covalent Bonding

acids

All ____start with H or end in COOH.

decreases

As the number of shared electron pairs increases, bond length _____.

Molecular Dot Structures

Count electrons-all valence electrons must appear in final structure. Follow octet rule. Remember how many bonds each ype of atom makes.(One for each extra electron needed). Mostly nonmetals.

Molecuar substances

Made of molecules which are loosely held together-van der Waals or London Dispersion forces (weakest). Tend to be liquids, gases or low melting solids. Melting molecular solids involves seperating molecules from each other. Most are insulators.

Polar bonds

formed when two atoms of unequal electronegativity are bonded The bond has a dipole moment because of the d+ and d- poles.

Lewis Structures

formulas in which atomic symbols represent nuclei and inner-shell electrons, dot-pairs or dashes between two atomic symbols represent electron paris in covalent bonds, and dots adjacent to only one atomic symbol represent unshared electrons

hybrid orbitals

orbitals of equal energy produced by the combination of two or more orbitals on the same atom.

lone pairs

pairs of valence electrons that are not involved in covalent bond formation, unshared pairs of electrons.

Exothermic

reactions occur when more energy is released forming new bons than is required to break bonds in the initial reatants.

Endothermic

reactions occure when a great amount of energy is required to break the existing bonds in the reactants than is released when the new bonds form in the product molecules.

hybridization

the mixing of two or more atomic orbitals of similar energies on the same atom to produce new hybrid atomic orbitals of equal energies

VSEPR model

valence shell electron pair repulsion, this model is based on an arrangement that minimizes the repulsion of shared and unshared pairs of electrons around the cenral atom. The repulsions among electron pairs in a molecule result in atoms existing at fixed angles to each other. Bonding and nonbonding pairs will arrange themselves around an atom so that they are as far from each other as possible.

symmetrical

elements of the design are centered or evenly divided horizontally and vertically on a page

pi bond

formed when parallel orbitals overlap to share electrons. The shared electron pair of a _____ ____ occupies the space above and below the line that represents where the two atoms are joined together. A multiple bond consists of one sigma bond and at least one ___ bond. A double covalen bond has one sigma bond and one ___ bond. A triple covalent bond consists of one sigma bond and two ___bonds.A ___bond always accomplanies a sigma bond when forming double and triple bonds.

triple covalent bonds

formed when three pairs of electrons are shared between two atoms.

trigonal bipyramidal

-central atom bonded to 5 other atoms -no lone pairs on central atom ex: PCl5 equatorial angle: 120 axial angle: 90 hybrization of sp3d.

octahedral

-central atom bonded to 6 other atoms -no lone pairs on central atom ex: SF6 angle: 90 Hybridation of sp3d2

mono

1

deca

10

Tetrahedral geometry

109.5; 4 shared pairs around central atom; no unshared pairs on central atom hybridization of sp3.

trigonal planar geometry

120; 3 shared pairs around central atom; NO unshared pairs on central atom. sp2

di

2

tri

3

tetra

4

penta

5

hexa

6

hepta

7

octa

8

nona

9

polar covalent bond

A covalent bond between atoms that differ in electronegativity. The shared electrons are pulled closer to the more electronegative atom, making it slightly negative and the other atom slightly positive.

structural formula

A molecular model that uses symbols and bonds to show relative positions of atoms; can be predicted for many molecules by drawing the Lewis structure.

nonpolar covalent

Electronegativity difference of 0-0.4

polar covalent

Electronegativity difference of x>0,4-1,4

ionic bond

Electronegativity difference of x>1.4

coordinate covalent bond

Forms when one atom donates a pair of electrons to be shared with an atom or an ion that needs two electrons to become stable.

greater melting point and boiling point

Greater dipole-dipole interactions means _____ _________________.

indicate the number present by using prefix + root of the second element + -ide.

How would you name an acidic non-aueous solution?

hydro+root of the second elemnt + -ic then acid.

If there is no oxygen in the compound which prefixes and suffixes will you use to name the acid

Polyatomic Ion Dot Structures

Same as molecular dot structures, except electrons must be added or subtracted to account for ion charge. Subtract electrons for + charge add for - charge. Make all structures as symmetrical as possible.

bond dissociation energy

The amount of energy required to break a specific covalent bond. Breaking bonds also requires the addition of energy. THe sum of the ___ _____ ___ values for all bonds ina compound is used to determine the amount of chemical potential energy available in a molecule of that compound. ___ ______ ___indicates the strength of a chemical bond because a direct relationship exists between nond energy and bond length.

bond angle

The angle formed by any two terminal atoms and the central atom. Predicted by the VSEPR.

covalent bond

The chemical bond that results from the sharing of valence electrons. In a ________ ____the shared electrons are considered to be part of the complete oter energy levelof both atoms involved ______ ______ generally occurs when elements are relatively close to each other on the periodi table. The majority of _____ ___ form between nonmetallic elements. This type of bond form a molecule.

hydrocarbon compounds

compounds with just hydrogen and carbon. saturated hydrocarbons all single bonds (alkanes).

Naming binary molecular compounds

The first element in the formula is always named first, using the entire element name. The second element in the formula is named using the root of the element and adding the suffix -ide. Prefixes are used to indicate the number of ams of each type that are present in the compound.

bond length

The strength of a covalent bond depends on how much distance seperates bonded nuclei. The distance between two bonding nuclei at the position of maximum attraction is called ____ ______.

expanded octet

The third group of compounds that does not follow the octet rule has central atoms that contain more than eight valence electrons. only for period three or higher.

insulators

dont conduct electricity. All nonmetals. not salts are insulators only when said not when melted. Loosely held.

sigma bond

a bond formed when two atomic orbitals combine to form a molecular orbital that is symmetrical around the axis connecting the two atomic nuclei, a single covalent bond that is formed when an electron pair is shared by the direct overlap of bonding orbitals. This results if the atomic orbitals overlap end t end, concentrating the electrons in a bonding orbital between two atoms.

Resonance

a condition that occurs when more than one valid Lewis structure can be written for a molecule or an ion. These are known as ____structures.

bonding orbital

a localized region where bonding electrons will most likely be found.

Expections to the octet rule

a small group of molecules has an odd number of valence electrons and cannot form an octet around each atom. Some compunds form with fewer than eight electrons present an atom. Bh3 is an example. A total of six electrons is shared less than eight this tends to be reactive and can share an entire pair of electrons donated by another atom. This is called a coordinate covalent bond. A third group of compounds that does not follow the octet rule has central atoms than contain more than eight valence electrons. This is called an expanded octet.

aqueous solution

a solution in which water is the solvent

bent geometry

an atom surrounded by 4 groups, two of which are lone pairs, has bond angle of 104.5°. Hybridization of sp3 or sp2.

oxyacid

any acid that contains hydrogen and an oxyanion-a polyatomic that contains oxygen.The name of the _ consists of a form of the root of the anion, a suffix andd the word acid. If the anion suffix ends in -ate it is replaced with the suffix -ic. If the anion ends in -ite the suffix is replaced with -ous.

dipole-dipole forces

attractions between oppositely charged regions of polar molecules.

hydrogen bonds

attractive forces in which a hydrogen covalently bonded to a very electronegative atom is also weakly bonded to an unshared electron pair of another electronegative atom.

linear geometry

bond angle is 180, Shape of a molecule with two covalent bonds and three lone pairs of electrons on the central atom. Hybridization of sp.

double covalent bonds

bonds involving 2 pairs of shared electrons (H::H).

trigonal pyramidal geometry

characterized by a Sp³ hybridized central atom with one pair of lone electrons. , the molecular geometry of a molecule with tetrahedral electron geometry and one lone pair.