Chem 101 Chapter 5

Covalent Bond

A bond that results from the sharing of electrons between atoms

Molecule

 

THe unit of matter held together by covalent bonds
bond length

-optimum distance between nuclei forming a bond.

-where net attractive forces are maximized and molecule is most stable

structural formula

-shows specific bonds between atoms

-gives much more info than a chemical formula

-uses lines between atoms to represent covalent bonds

 

chemical formula
lists the symbols of the compound’s constituent elements and uses subscripts to indicate the number of atoms of each element
bond dissociation energy (D)
the amount of energy that must be supplied to break a chemical bond in an isolated molecule in the gaseous state, and thus the amount of energy released when the bond forms

range of strength of bonds commonly encountered in naturally occuring molecules;

Ex. (C-H , C-C , C-O)

350-400kJ/mol
Lattice Energy (U)
The amount of energy that must be supplied to break an ionic solid into its individual gaseous ions and is thus a measurement of the strength of the crystal’s ionic bonds
polar covalent bonds

the large majority of bonds in which bonding electrons are shared unequally between two atoms but are not completely transferred 

Represented by delta (δ)

–  (δ+) for atom w/ smaller share

–  (δ-) for atom w/ larger share

electrostatic potential map

-uses cols to portray the calculated electron distribution in an isolated, gas-phase molecule

 -blue represents electron shortage (partial positive) and red represents electron surplus (partial negative)

nonpolar covalent bond

-the bond between the two atoms is equal

-occurs with diatomic molecules that contain a covalent bond between two identical atoms

Electronegativity (EN)

-The ability of an atom in a molecule to attract shared electrons in a covalent bond

-fluorine has the highest

-metallic elements have weakest

-highest top right decreases to lowest bottom left

what is bond polarity caused by
differences in electronegativity
electron affinity
the energy change that occurs when an electron is added to an isolated gaseous atom
ionization energy
the amount of energy needed to remove the highest-energy electron from an isolated neutral atom in the gaseous state

Lewis Structes

(Electron-Dot Structures)

represents an atom’s valence electrons by dots and indicates by the placement of the dots how the valence electrons are distributed in a molecule;
octet rule
states that main-group elements tend to undergo reactions that give them a noble-gas electron configuration with filled s and p sublevels in their valence electron shells
lone pairs
pairs of nonbonding electrons on each atom in a covalent bond
bonding pairs
the shared electrons between two atoms in a covalent bond
bond order

number of pairs ;of electrons shared in a covalent bond;

Delineated by lines

– is 1

= is 2

i dont have a button with three lines but you get the idea

Coordinate Covalent Bonds

Bond formed whenone atom donates both electrons (a lone pair) to another atom that has a vacant valence orbital.

Ex.

ammonium ion (NH4+) forms when two lone pair electrons from the nitrgen atom of ammonia (NH3) bond to (H+)

N,O,P, and S form these regularly

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