Chemistry - Unit 6 - Covalent Bonds

covalent bond

atoms held together by sharing electrons, usually occurs so that atoms attain electron configurations of noble gases, occurs between 2+ nonmetals

molecule

neutral group of atoms joined together by covalent bonds

diatomic molecule

molecule with two atoms

molecular compound

compound composed of molecules, tend to have relatively lower melting and boiling points than ionic compounds

molecular formula

chemical formula of a molecular compound, shows how many atoms of each element a molecule contains

single covalent bond

two atoms held together by sharing a pair of electrons

structural formula

represents the covalent bonds by dashes and shows the arrangement of contently bonded atoms

unshared pair/ione pair/nonbonding pair

a pair of valence electrons that is not shared between two atoms

double covalent bond

bond that involves two shared pairs of electrons between two atoms, contains one sigma bond and one pi bond

triple covalent bond

bond formed by sharing three pairs of electrons are shared between two atoms, contains one sigma bond and two pi bonds

coordinate covalent bond

covalent bond in which one atom contributes both bonding electrons, the shared electron pair comes from one of the bonding atoms

polyatomic ion

a tightly bound group of atoms (nonmetals) that has a positive or negative charge and behaves as a unit

bond disassociation energy

energy required to break two covalently bonded atoms, the stronger the bond, the more energy that's needed

resonance structure

a structure that occurs when it is possible to draw 2+ valid electron dot structures that have the same number of electron pairs for a molecule or ion

valence electrons

electrons on the outermost shell (s and p sublevels) and participate in chemical bonds

molecular orbital

orbitals that apply to the entire molecule

bonding orbital

molecular orbital that can be occupied by two electrons of a covalent bond

sigma bond (σ) (single bond)

when two atomic orbitals combine to form a molecular orbital symmetrical around the axis connecting two atomic nuclei

pi bond (π)

when a pi molecular orbital is filled with two electrons, bonding electrons are most likely to be found in sausage shaped regions below and above the bond axis of bonded atoms

VSEPR Theory (Valence Shell Electron Pair Repulsion)

the repulsion between electron pairs causes molecular shapes to adjust so that the valence electron pairs stay as far apart as possible, minimizes the repulsion of atoms around the central atom

orbital hybridization

provides information about molecular bonding and shape, several atomic orbitals mix to form the same total number of equivalent hybrid orbitals

molecular structure

indicates the types and numbers of each atomic molecule (ex: H₂O contains 2 Hydrogen atoms and 1 Oxygen atom)

bond

shared pair of electrons

tetrahedral

4 atoms bonded to the central atom, 0 lone pairs, 109.5° bond angle (ex: CH₄)

triagonal pyramidal

3 atoms bonded to the central atom, 1 lone pair, 107° bond angle (ex: NH₃)

bent

2 atoms bonded to the central atom, 2 lone pairs, 104.5° bond angle (ex: H₂O)

triagonal planar

3 atoms bonded to the central atom, 0 lone pairs, 120° bond angle (ex: BF₃)

bent

2 atoms bonded to the central atom, 1 lone pair, 120° bond angle (ex: SnCl₃)

linear

2 atoms bonded to the central atom, 0 lone pairs, 180° bond angle (ex: CO₂)

mono-

x₁, not used for the first atom

di-

x₂

tri-

x₃

tetra-

x₄

penta-

x₅

hexa-

x₆

hepta-

x₇

octa-

x₈

nona-

x₉

deca-

x₁₀

nonpolar covalent bond

when atoms in the bond pull equally and bonding electrons are shared equally, has an electronegativity difference of ≤ 0.4

polar covalent bond (polar bond)

covalent bond between atoms in which electrons are shared unequally, has an electronegativity difference of 0.5 ≥ 1.9

polar molecule

one end of the molecule is slightly negative and the other end is slightly positive, the molecule must be a polar bond AND have molecular symmetry

dipole (dipolar molecule)

molecule with two poles

van der Waals forces

two weakest attractions between molecules

dipolar interactions

occur when polar molecules are attracted to one another

dispersion forces

weakest of all molecular interactions, caused by motion of electrons

hydrogen bonds

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

ionic bond

electronegativity difference ≥ 2.0