Chem 101 Module 3

Ionic Compound

Rigid and brittle, high melting and boiling points, not electrically conductive when solid but only when melted, electrons shared between oppositely charsged cations and anions and held together by the force of electrostatic attraction

Ionic compounds in water

solube, can then conduct electricity

How do binary ionic compounds form?

When a metal loses an electron and donates them to a nonmental

What is a covalent bond?

A bond formed between two nonmetal that is the mutal attraction of atoms for a shared pair of electrons

What are the 3 exceptions to the octet rule? 

1. Odd electron molecules/free radicals have an odd number of valence eelectrons

2. Electron-deficient moleucles have a central atom with fewer electrons than needed for a noble gas configuration

3. Hypervalent molecules have a central atom that has more electrons than needed for a noble gas configuration

What is the VESPR theory?

The valence shell electron-pair theory that assumes electron pairs in the valence shells will adopt an arrangement than minimizes repulations between these paris by maximizing the distance between them

What is the VESPR theory used for?

To predict the molecular geometry of a molecule using the number of bonds and number of lone pairs 

Define iso electronic

When two elements ahve the same electron configuaration and only differ in the number of protons in the nucleus 

What are the typical traits of covalent compounds?

Gases under normal conditions, soft solids with low melting and boiling points, insoluble and are poor conductors of electricity in any state

Covalent compounds are formed between _____ elements

nonmetal

Define intermolecular distance

the ideal distance between to molecules that is the most stable where they can share electrons

Bond length

Determined by the intermolecular distance, distance where they lowest potential energy is achieved

Pure covalent bond (definition and value)

EN < 0.4, electrons are shared equally between atoms and each atom has an equal electron density

Polar covalent (value and definition)

EN between 0.4 and 1.8, there is a partial postive and negative charge and electrons are not shared equally 

When indicated polary the arrow points towards the _____ end

negative

Electronegativity definition

The measured tendency of an atom to attract electrons towards itself, a larger value attracts more electrons

Electronegativity _______ from left to right and ________ from top to bottom of the periodic table

increases; decreases 

Electron affinity vs electronegativity

Electron affinity is used during the creation of an anion for energy adding an electron while electronegativity is used in bonding situations only for how man an atom attracts an electron

How do you name basic ionic compounds with only monoatomic ions?

Name the first metal and then name the anion with the ending changed to -ide

How do you name an ionic compound with a polyatomic ion?

Name the cation and don’t change the name of the polyatomic ion

How do you name an ionic compoudn with a cation that has a variable charge?

Name the cation and specifiy the charge with a roman numeral and change the anion to the -ide ending

How do you name an ionic hydrate?

First name the compound without the water molecule then add the appropriate greek prefix for the hydrate

4 greek prefix

tetra

5 greek prefix

penta

6 greek prefix

hexa

7 greek prefix

hepta

9 greek prefix

nona

10 greek prefix

deca

What are the rules for naming molecular covalent compounds? 

1. Name the more metallic element and add a greek prefix if there are 2+ present

2. Name the more nonmetallic ending with the appropriate greek prefix and change the ending to -ide

How do you name binary acids?

add the prefix hydro, name the nonmetallic element and change the ending to -ic, add acid as a second word

What is an oxyacid?

A compound made up of H, O and at least one other element that are bonded in a way that gives acidic properties to the element

How do you name oxyacids? (endings with ate = _____ and endings with ite = _____)

start with the root name of the anion and change the endic to -ic;-ous

Sulfate or Sulfite → _____ when naming as an acid

Sulfuric; sulfurous

Phosphate → when naming as an oxyacid

Phosphoric 

What is the duet rule?

The idea that Hydrogen only needs two valence elctrons

When drawing a lewis strucutre, the _____ electronegative goes in the center

least

Formal charge definition

The hypothetical charge if electrons in bonds were redistributed equally between the atoms

Formal charge formula

FC = number of valence shell electrons - number of lone pair electrons - ½ the number of bonding electrons

How can you use formal charge to predict molecular structure? (3)

The preferred strucutre will have a FC as close to zero as possible, adjacent atoms will have an FC of 0 or opposite signs, and more electronegative atoms will have negative FCs

Define resonance

A situation when one Lewis structure is insufficient and the average of multiple structures is observed

What are resonance forms?

When there is the same arrangement of atoms but different electron arrangements

How do you indicate a resonance hybrid?

←—→

Define bond angle

the angle between any tw bonds that include a common atom

Define bond distance

The distance between the nuclei of two bonded atoms along the straight line joining the nuclei measured in Angstroms

Electron geometry for two regions of electron density

linear

Electron geometry for three regions of electron density around an atom

Trigonal planar

Electron geometry for four regions of electron density around an atom

Tetraderal

Electron geometry for five electron regions around an atom

Trigonal bypyramidal

Electron geometry for 6 regions of electron density around an atom

Octahedral

Molecular geometry vs electron geometry

Electron geometry doesn’t differentiate between bonds and lone pairs

Which has a stronger repulsion: lone pair - lone pair or bonding pair - bonding pair

lone pair - lone pair

Rank from largest to smallest: double bond, triple bond, lone pair, single bond

lone pair > triple bond > double bond > single bond

Molecular geometry from 2 electron regions and no lone pairs

Linear

Molecular geometry for 3 electron regions and no lone pairs

trigonal planar

Molecular geometry for 3 electron regions and 1 lone pair

bent/angular

Molecular geometry for 4 electron regions and no lone pairs

Tetrahedral

Molecular geomery for 4 electron regions and one lone pair

Trigoanl pyramid

Molecular geometry for 4 electron regions and 2 lone pairs

Bent/angular

Molecular geometry for 5 electron regions and no lone pairs

Trigonal bipyramidal

Molecular geometry for 5 electron regions and 1 lone pair

Seesaw

Molecular geometry for 5 electron regions and no lone pairs

Molecular geometry for 5 electron regions and 2 lone pairs

T-shape

Molecular geometry for 5 electron regions and 3 lone pairs

Linear

Molecular geometry for 6 electron regions and no lone pairs

Octahedral

Molecular geometry for 6 electron regions and 1 lone pair

Square pyramid

Molecular geometry for 6 electron regions and 2 lone pairs

Square planar 

Molecular geometry for 6 electron regions and 3 lone pairs

T-shapes

Molecular geometry for 6 electron regions and 4 lone pairs

Linear

What is a bond dipole?

The separation of charge in a bond 

What is a dipole moment?

The description fo the separation of charge in the molecule as a whole, the sum of all the bond moments in a 3d space that takes into account molecular structure

Solid arrangement

tightly packed, regular pattern, vibrate in a fixed position and don’t move in relation to each other

Liquids

close together and no regular arrangement, remain essentially in constant contact but move past each other

Gas

molecules far apart with no regular arrangement, move independently of each other 

The phase of a substance depends on ____ and ____ of the molecules

intermolecular forces; kinetic energies

With an increase in temperature kinetic energy _____ and IMF _____

increases; decreases

Intramolecular forces

between atoms

Intermolecular forces

attractions between molecules, determine physical properties

What are the three types of Van der Waals Forces

1. Disperson/London

2. Dipole-Dipole

3. Hydrogen Bonding

Disperson forces 

the weak attractive forces between all particles becuase of the constant electron movement and temporary dipoles, increases with proximity and atomic size

Instantaneous dipoles

occur becuase electrons are in constant motion

Induced dipole

temporary dipole that forms when an electron is distorted by the instantaneous dipole of a neighboring atom

polarizability

how easy or different it is for an external charge to distort a molecule’s charge distribution 

dipole-dipole attractions

the attractive electrostatic forces bteween the partially positive end of one polar molecule and the partially negative end of another

Hydrogen bonding 

the strong dipole-dipole attraction that occurs when exceptionally strong dipoles attract, contains IM bonds between hydrogen and one of the three most electronegative elements

what are the three most electronegative elements

F, O, N

Rank covalent and the three Van Der Waals forces in terms of strength

Covalent bonds > hydrogen bonds > dipole-dipole > dispersion forces