Chapter 6 - Covalent Bonds

6.1 Intro to covalent bonds 6.2 Covalent Nomenclature 6.3 Electron Dot Notation and Lewis Structures 6.4 Polarity and Intermoleular Forces 6.5 VSEPR Theory

covalent bond

A chemical bond that involves sharing a pair of electrons between atoms in a molecule

What're covalent bonds generally formed by?

The are generally formed by 2 non-metals or 1 non-metal and 1 metalloid

How can covalent bonds form?

through atoms of non-metals coming together and combining like puzzle pieces into to covalent bonds by sharing their VEs.

physical property - crystalline structures

Covalent Compounds can form crystalline structures because their atoms share electrons, thus creating a stable, repeating pattern in a 3-dimensional structure

physical property - low melting points

Covalent Compounds have low melting points because their forces of attraction are weak. Meaning it will take less heat/energy to break/split bonds

physical property - liquid/gases @ rm temp.

Covalent compounds have weak forces of attraction that is not enough for them to maintain a solid composition.

physical property - Soft and Brittle

Covalent Compounds have weak forces of attraction which lets layers slide, making them soft. They are brittle because the bonds can be broken easily

physical property - don't transfer heat very well

physical property - little energy release

Covalent compounds have little energy release because when forces of attraction are overcome. This is because it takes little force of attraction to connect molecules, meaning it will take little energy to separate them

physical property - electrical conductivity

Covalent Compounds don't conduct electricity well when dissolved because they don't break into ions, making no way for electricity to travel as there is no free-flowing energy/charge in the solution

How are covalent compounds named?

They are named using prefixes because elements can bond in multiple ways

naming covalent compounds rule #1

the the first element is an single atom we DO NOT use mono

naming covalent compounds rule #2

second element will always use a prefix and make it end in -ide

Naming Binary Covalent Compounds

(prefix of element #1 [besides mono])(element #1)

+ (prefix of element #2)(element #2)(replace with -ide)

electron-dot notation

shows an atom that is ready to bond and the VE are represented by dots and the AS represents the rest of atom

Lone Pairs

A set of a pair of a electrons that belong to an atom but is not involved with the bonding

How to draw an element's electron Dot Notation

1. Write elements AS

2. IMAGINE a box around the AS

3. Determine the # of VE in the atom by looking at the G#

4. Draw dots around the AS (each side must have one before you pair them)

Lewis Structure

A structural formula in which electrons are represented by dots; dot pairs or dashes between two atomic symbols represent pairs in covalent bonds

How to Draw a Lewis Structure

1. add the valence electrons for all the atoms in the molecule

2. determine the central atom (least electro-negative besides Hydrogen)

3. draw single bonds in the form of lines towards the central atom

4. put all remaining VEs on atoms as lone pairs (except H)

5. Turn lone pairs into double or triple bonds if needed to give every atom an octet/duet by replacing them towards the atoms of higher electro-negativity

single bond

long/weak

double bonds

medium/moderate - sharing 2 pairs of e- between 2 atoms

triple bonds

short/strong - sharing 3 pairs of e- between 2 atoms

expanded octets

molecules that posses atoms utilizing an expanded octet = hypervalent

Polarity

the distribution of electrical charge over the atoms joined by the bond

polar molecule

molecule with an unequal distribution of charge, resulting in the molecule having a positive and a negative region of charge

nonpolar molecule

molecule with a symmetrical distribution of charge that is, resulting in the molecule having no regions of partial charge.

polarity range

dependent on what source you use

non polar covalent bond

the difference in EN between 2 atom will be 0<x<=0.40 - present in covalent compounds

Polar Covalent

the difference in EN between 2 atom will be 0.4<x<=1.80 - present in covalent compounds

Ionic

the difference in EN between 2 atom will be 1.8<0- present in ionic compounds

dipole moment

the mathematical product of the separation of the ends of a dipole and the magnitude if charges AKA the dipole avg

the product of the charge and the separation distance (bigger atom = bigger dipole moment)

when there is uneven distribution of charge within the molecule

intramolecular force

the force (attraction) between atoms within a compound

intermolecular force

the force (attraction or repulsion) that is between separate molecules

London dispersion forces

the result of attraction between separate molecules due to e- moving which create a temporary dipole

• present in ALL covalent compounds

• highest possible IMF for noble gasses and non-polar covalent compounds

dipole-dipole forces

the result of attraction between separate molecules due to permanently existing dipoles

• present in ALL POLAER covalent compounds

• highest possible IMF for polar covalent compounds

hydrogen bond

weak attraction between a hydrogen atom and another atom (N,O,F)

• present in ALL POLAR covalent compounds that have these three elements with H

• Highest Possible IMF that has these possibilities

Molecular Geometry

Describes the specific shape of the molecule as a result of e- wanting their own space

VSEPR stands for

Valence Shell Electron Pair Repulsion

electron geometry

geometry that describes a generalized shape since they want their own space (atoms and electrons will affect the shape)

No lone pair on A

EG and MG is the same

VSEPR Designation

A = central atom

X = atoms bonded to A

E = lone pair of E-