Chem Exam 4

Lewis symbol

valence e- represented as dots around a main group element symbol

How many valence e- does a element need to be stable

8

Octet rule

atoms bond in a way that gives them 8 valence e- to become a stable electron configuration similar to a noble gas

metal + non metal e- characteristics

e- are transferred

non metal + non metal e- characteristics

e- are shared

metal + metal e- characteristics

e- are pooled

metal + non metal bond

ionic bond

non metal + non metal bond

covalent bond

metal + metal bond

metallic bond

ionic bonding

transfer of e- from metal to non metal

Crystalline lattice

array of points representing atoms, ions, or molecules of a crystal, arranged at different sites on a 3 dimensional space

Ionic bonds in crystalline lattice

form crystalline lattice composed of alternating cations and anions

potential energy of a crystalline lattice decreases…

as oppositly charged ions come closer together (E is released as heat when lattice forms)

Coulumbs Law

describes the electrostatic force between two charged particles, which is directly proportional to the product of their charges and inversely proportional to the square of the distance between them

Lattice Energy

E associated with the formation of a crystalline lattice by cation and anions in the GASEOUS state (L.E makes up the difference between I.E + E.A and ΔH°f

Ionization Energy (I.E)

the energy required to remove an electron from a neutral atom or ion in its gaseous state

Electron Affinity (E.A)

the change in energy when an electron is added to a neutral atom to form a negative ion

Lattice Energy (L.E) is calculated using…

Born - Haber cycle

Born-Haber cycle

a hypothetical series of steps that represent the formation of an ionic compound from its constituents elements (E tracking / book keeping)

Trend in L.E ion size

L.E becomes smaller in magnitude down a column (as the size of the ion increases there is a larger distance between nuclei)

Trend in L.E ion charge

L.E increases with increasing ionic charges

Lewis Structure

bonding atoms share e- until both obtain an octet (8e-) → when counting octets, the shared e- is counted for both atoms

The more bonds between atoms…

the stronger and shorter those bonds are

Step one for drawing Lewis structure

Calculate total # of valence e- in a molecule (sum of valance e- in each atom) → charges must be considered (if present)

Step 2 of drawing Lewis Structures

Sketch a skeletal structure

→ H are always terminal (not central)

→ most electronegative atom is central (F is most EN)(Fr is least EN)

Step 3 of drawing Lewis Structures

distrubute valence e- among atoms giving octets to as many atoms possible

→ start with 1 bond (2e-) between each pair of atoms

→ distribute remaining pairs as lone pairs (terminal → central)

Step 4 of drawing Lewis Structure

if any atoms lack a octet, then convert lone pairs of e- into double/triple pairs until octet is reached