Chemistry Chapter 4 Arrangment of Electrons in Atoms

Chemical Bond

a mutal attraction between protons and electrons of an atom

Ionic Bonding

Electrons are transferred

Covalent

Electrons are shared

Non-polar Covalent

pair of electrons shared equally on both sides

Range from covalent bonds to ionic bonds

gradual continum that changes (one does not go away)

Ionic Bonding

Large difference in electronegativity

non-metals

who has high electronegativity?

metal

who has low electronegativity?

metal+nonmetal

an ionic bond is a bond between…?

#s

without…..you do not know if a covalent compound is polar or non-polar

Electron Dot Notation

show the valence electrons on an atom
Go all the way around the symbol before pairing up electron dots

Ionic Bonding

Ionic compound and Formula units are both part of…?

Ionic compound

when cations and antions combine they must make a neutral compound

Formula Unit

simplest ratio of cations to anions (of neutral compound)

Ionic Bonding

strength - strong bonds/attractions
crystal lattice - extremely organized
lattice energy - gas ions make 1 mol of solid compound (decrease in energy with energy released)

an ionic compound, also covalent w actual # of atoms in molecule

when do we talk about relative # of atoms?m

molecule

a neutral group of atoms held together by covalent bonds (covalent bonds)

molecular compound

a compound with molecules as its simplest unit

chemical formula

shows element and actual or relative # of atoms of each element in compound

molecular formula

the # of atoms and the element that is present in one molecule of compound

diatomic molecule

a molecule with 2 atoms of the same or different elements

diatomic elements

2 of the same elements

BrINClHOF

7 diatomic elements are…?

Bond Length

the average distance that gives the minumum energyBon

Bond Energy

the energy required (POSITIVE ENERGY) to break bond (chemical), breaks bonds and forms 2 neutral isolated atoms

Longer bonds are weaker, have to put in less energy to break it

What is the relationship between bond length and bond energy?

All atoms wants to look like a noble gas (need 8 valence electrons)

Octet Rule

REMEMBER
H - 2 electrons - 1 bond
Be - 4 electrons - 2 bond
B - 6 electrons - 3 bond
C - beyond…want full 8

THE ELEMENTS THAT DO NOT FOLLOW THE OCTET RULE
REMEMBER THEM!!

Lewis Strucutres

used for covalent compounds
Rules:
Count the total # of valence electrons (most F/ energy)Distribute electrons to satisfy the octet rule and show bonding pairs.
Put the least electronegative atom in the center
Attach other atoms to it (usually)
Carbon goes in the middle
give an octet to each atom that needs one
If not enough electrons, they need to do double duty
if too many electrons, put extras on the central atom
Double Check
Have you placed all electrons?
Does each atom have an octet that should?

Molecular Geometry

shape of molecule detemrines polarity
polarity detemrines characteristics (shape is based on)
characteristics include: high/low boiling and melting
high or low surface tension, how fast material diffuses
Capilary Action: liquid —> straw in liquid is higher
VSEPR Theory

VSEPR Theory

Valence shell electron pair repulsion

Ionic

very high melting/boiling point
hard and brittle
has conductivity (metal or dissolved)

Covalent

low melting/boiling point, soft (hardness), no conductivity

breaking bonds between positive and negative ions

melting means

mol

breaks an attraction, they are their own molecules - separate

Good Conductors

charge carrier (ion, e-), must be mobile or able to move

Intermolecular Attractive Forces (IMAFs)

inter, intra
Dipole-Dipole, Hydrogen Bonding, London DIspersion Forces

“weakest but important to non-polar substances”

inter

between two different moelcules

intra

inside of one molecule
attraction between two molecules are weak significant, weaker than, covalent bonds

Dipole-Dipole IMAF

Dipole, di(two)pole, caused by separation of charge, occurs between polar molecules
See Sketch

Dipole

in a polar molecule, one “end” is slightly positive, the other “end” is slightly negative

Hydrogen Bonding

Speical case of dipole-dipole IMAF
Not a bond (is an attraction)
If H is covalently bonded to N, O, F (3 most eneg smallest elemnts)
Then an especially strong attraction will form between that H and the N, O, F or a different molecule
Occurs between polar molecules

London Dispersion IMAF

indued dipole-induced dipole IMAF
electrons always moving around the nucleus
Statistically, they will “pile up”
this forms a slgihtly negative area
which induces a dipole in the next particle
Occurs between everything, BUT important in non-polar ones

decrease their potential energy, thus creating more stable arrangmeents of matter

As atoms bond with each other, they

0% nonpolar and covalent

The percentage ionic character and the type of bond in Br2 (electronegativty for Br is 2.8) is…?

weaker

compared with molecular bonds, the strength of intermolecule forces is….?

bond angles associated with molecular shape, the shape of molecules

VSEPR theory is amodel for predicting

3

How many more electrons does nitrogen need to satisfy the octet rule?

never hydrogen

In drawing a Lewis strucutre, the central atom is …?

chlorine

In the three molecules, O2, HCL, and F2, ahat atom would have a partial negative charge?

oxygen

multiple covalent vonds may occur in atoms that contain carbon, nitrogen or…?

hydrogen bonding

the reason the boiling point of water is higher than the boiling point of hydrogen sulfide (H2S) is partially explained by?

O and Cl

The pair of elements that forms a bond with the least ionic character is?

are usually much weaker than the dipole-dipole forces

Dipole-Dipole forces are considered the most important forces in polar substances because the London dispersion forces present in polar substances

beryllium and boron

Exceptions to the octet rule include…?

lower potential energy

Compared with energies of neutral atoms, a crystal lattice has…?

absorb and re-emit light of many wavelengths

To appear shiny, a material must be able to?

polar molecule

Iodine monochloride (ICl) has higher boiling point than bromine (Br2) partly because iodine monochloride is a(n)…?

inversely related to bond energy, is the average distance at which kinetic energy is at a maximum

Bond Length..?

dipole

the equal but opposite charges present in the two regions of a polar molecule create a(n)…?

NH3 and H2O

The substance whose Lewish structure shows three covalent bonds is?

contains a double or triple bond and shows resonance

bonding in molecules or ions that cannot be correctly represented by a single Lewis Strucutre

ratio of combined ions present in a sample

The chemical formula for an ionic compound represents the

NH3

The following molecules contain polar bonds. The only polar molecule is…?