Chapter 5

Question 1

Lewis Dot structures

Answer 1

Lewis Dot structures are made by adding dots around an element. Each dot represents one valence electron. You start by writing the symbol of the element (O for oxygen) and then make dots on the 4 sides of it. each side can only have a pair of electrons (2). To find how many valence electrons there are you go by group numbers. For example, Group 1 will have 1 valence electron, 2 will have 2 and so on. You can have a max of 8 electrons which is a complete octet
EX: Fluorine there will be 7, meaning 3 pairs and one lone pair (1, non-bonding electrons).
*pg90

Question 2

Single bond from lewis structures

Answer 2

A bond formed from 2 electrons. The lone pairs are what can go and bond with another element to make a compound. (EX: the lone pair of Fluorine can bond with another Fluorine’s lone pair to form F2)
*pg90

Question 3

Double bonds from lewis structures

Answer 3

Double bonds use 4 electrons. This can be done when there’s 2 lone pairs (or more), one of the lone pairs joins with the other by using another one of the lone pairs from its elements, this way you will be left with no lone pairs (if you had 2).
EX: in Oxygen theres 2 lone pairs, so to form O2, you join one side of the lone pairs by using another side’s lone pair. This way you will be left with 2 pairs and on double bond.
*pg91

Question 4

Triple Bonds from lewis structures

Answer 4

This uses 6 electrons. Similar to double bonds but you need 3 lone pairs (or more), while one lone pair connects with another element’s lone pairs, it also uses the other 2 lone pairs to form the triple bond.
*pg91

Question 5

Formal charges

Answer 5

They don’t give the actual charges of the atoms, they just let us know if the sharing (bonding) of valence electrons bw 2 or more elements is in the best way possible. The best outcome is if the formal charge is 0 on all the atoms, if that’s not possible we try to achieve the lowest possible charge.
Formula: FC=V - 1/2B -L
— V is the number of valence electrons
— B is the number of bonding electrons (sticks)
— L is the number of non bonding electrons
This is calculated for each element in a compound seperately
*pg91/92

Question 6

Resonance structures

Answer 6

Two or more structures that are often used when there are double or triple bonds in molecules along with one or more lone pairs of electrons. This is mostly when you swith a double or triple bond from one element to another.
for example if a compound has 2 Oxygens like CO2, in one resonance structure

Question 6

Resonance structures

Answer 6

Two or more structures that are often used when there are double or triple bonds in molecules along with one or more lone pairs of electrons. This is mostly when you with a double or triple bond from one element to another.
for example if a compound has 2 Oxygens like CO2, in one resonance structure Oxygen 1 will have a double bond with C while in another Oxygen 2 will.
These are structures in which only nonbonding electrons, and double and triple bonds can move around.
*pg93

Question 7

Resonance Hybrid

Answer 7

When 2 resonance structures have an equal bond length and are both a good option to use. This can be either demonstrated by showing both the compounds with a double arrow bw them or one compound wish dashed lines for the second double bond that would be in the second structure.
A molecule can also have 2 or more non-equivalent resonance structures, in this case the resonance hybrid is a weighted average if them (diagram shown in picture)
*pg93/94

Question 8

Bond length

Answer 8

The distance between 2 nuclei that are bonded to one another

*pg95

Question 9

Bond Dissociation Energy (BDE)

Answer 9

the energy required to break a bind homolytically.

*pg95

Question 10

Homolytic bond cleavage

Answer 10

when one electron of the bond being broken goes to each fragment of the molecule. In this process 2 radicals form
*pg95

Question 11

Heterolytic Bond cleavage

Answer 11

AKA dissociation. In this case both the electrons of the electron pair that make up the bond end up on the same atom; This forms both a cation and an anion.
*pg95

Question 12

Trend bw bond length abd BDE

Answer 12

For similar bonds, The higher the bond order, the shorter and stronger the bond.
*pg95
Similar bond meaning Carbon-carbon bonds compared to other C-C bonds, and C-O bonds compared to other C-O bonds.
The longer the bond, the weaker it is and vice versa.
*pg96

Question 13

Bond order

Answer 13

The number of bonds between adjacent atoms, so a single bond has a bond order of 1 while a triple bond has a bond order of 3

Question 14

s and p orbitals compared to bond length

Answer 14

The greater the s character in the hybrid orbitals, the shorter the bond (because s orbitals are closer to the nucleus than p orbitals) A greater percentage of p character leads to a longer bond.

Question 15

Covalent bonds

Answer 15

A covalent bond is formed between atoms when each contributes one or more if its unpaired valence electrons. The electrons are shared by both atoms to help complete both octets

Question 16

Polarity of covalent bonds

Answer 16

When a molecule has a dipole moment. A bond is polar if the electron density between two nuclei is uneven, which occurs if there is a difference in electronegativity of the bonding atoms, and the greater the diff, the more uneven the electron density and the greater the dipole moment.
A bond is nonpolar if the electron density bw the 2 nuclei is even. This occurs when there is little to no difference in electronegativity bw the bonded atoms (mostly when its 2 of the same element bonded)
*pg97

Question 17

Coordinate covalent bond

Answer 17

when one atom will donate both of the shared electrons in a bond.
For example when element has a pair of non-bonded electrons and its boning with an element that doesn’t have any electrons. Instead of each element contributing one electron to bond in this case, only one element is contributing, and both the electrons.
*pg97

Question 18

Lewis Base vs lewis acid

Answer 18

Lewis base is When a molecule donates a pair of electrons. These bases can act as a ligand, or a nucleophile (nucleus-loving), so all 3 terms are synonymous
Lewis acid is when a molecule accepts a pair of electrons. Also can be called electrophile (electron loving)
These are both part of coordinate covalent bonding. base is the one that has the non bonding electron pair and acid is the one that doesn’t and isn’t contributing anything.
*pg98

Question 19

Ionic Bond

Answer 19

When a bond is formed by gaining or losing electrons. For example in NaCl, The Na giving its electron to Cl creating a cation (Na+) and an anion (Cl-). They’re held together by electrostatic attraction between a cation and anion.
*pg99

Question 20

What do you need to form an ionic bond between a metal and a non-metal

Answer 20

There has to be a big difference in electronegativity between the 2 elements.
*pg99

Question 21

The strength of ionic bonds

Answer 21

The strength of the bond is proportional to the charges on the ions, and it decreases as the ions get farther apart, or as the ionic radii inc. We can use this to estimate the relative strength of the ionic systems.
For EX: comparing MgS and NaCl, in MgS the Mg has a +2 charge and S ion has a -2 charge. While for NaCl, Na has +1 and Cl has -1, Therefore the MgS bond is expected to be about 4 times stronger than NaCl bond, assuming the size of the ions are very nearly the same.
*pg99

Question 22

VESPR theory

Answer 22

Valence Shell Electron-pair Repulsion.
The theory through which the shapes of simple molecules is predicted. This goes by one rule: Since electrons repel one another, electron pairs, whether bonding or non bonding, attempt to move as far away as possible.
*pg99/100 (table in textbook)

Question 23

Hybridization

Answer 23

used In order to rationalize observed chemical and structural trends. for this, you imagine a mathematical combination of atomic orbitals centered on the same atom to produce a set of composite, hybrid orbitals
*pg100

Question 24

the percentages of s characters and p character in a given sp^x hybrid orbitals

Answer 24

X orbital. s character p character

1. 50%. 50%
2. 33%. 67%
3. 25%. 75%
   * pg100

Question 25

how to determining hybridization in most atoms in simple molecules

Answer 25

Add the # of attached atoms (the number of elements connected to that element) to the # of non-bonding electron pairs and use this table
[in order of electron groups (#atoms + #lone pairs) : hybridization : Bond angles : Orbital geometry] :
2 : sp : 180º : Linear
3 : sp^2 ; 120º : Trigonal planar
4 : sp^3 : 109.5º : Tetrahedral
*pgg103

Question 26

Sigma(σ) bonds

Answer 26

A σ consists of 2 electrons that are localized bw 2 nuclei. it is formed by the end-to end overlap of one hybridized orbital (or an s orbital in the case of H)
basically: the overlap of the orbitals.

Question 27

Pi (π) bonds

Answer 27

A π bond is composed of 2 electrons that are localized in the region that lies on opposite sides of the plane formed by the 2 bonded nuclei and immediately adjacent atoms, not directly bw the 2 nuclei as with σ bond. It is formed by the proper, parallel, side-to-side alignment of 2 unhybridized p orbitals on adjacent atoms. In any multiple bond, there is only one σ bond and the rest are all pi bonds, so:
A single bond is composed if 1 σ bond
a double bond : 1 σ and 1 pi
triple bond: 1 σ and 2 pi
*pg105/106

Question 28

Molecular Polarity

Answer 28

A molecule as a whole can be polar or non-polar. If a molecule has no polar bonds, it can’t be polar, if it has 2 or more symmetrically oriented polar bonds they cancel out, but if they are not symmetrical the molecule will be polar.
*pg107

Question 29

Intermolecular forces

Answer 29

Liquids and solids are held together by these forces, such as dipole-dipole and London dispersion forced. These are the relatively weak interaction that take place bw neutral molecules
*ph108

Question 30

Dipole-dipole forces

Answer 30

Polar molecules are attracted to ion dipole forces. Dipole-dipole forces are the attractions between the positive end of one polar molecule and the negative end of another polar molecule.
*pg108

Question 31

How can one produce a dipole-induced dipole force

Answer 31

A permanent dipole in a non polar molecule may induce a dipole in a neighbouring non-polar molecule, producing dipole-induced dipole force.
*pg108

Question 32

London dispersion forces

Answer 32

The attractions Caused by an instantaneous dipole in a nonpolar molecule which may induce a dipole in a neighbouring nonpolar molecule. These are very weak and transient interactions between the instantaneous dipoles in nonpolar molecules. These are default force, all a molecule needs to do to experience these are have electrons (every molecule has these ones)
*pg108

Question 33

Which ones are the weakest forces

Answer 33

London dispersion

Question 34

What makes the dispersion forces stronger

Answer 34

As the size of the molecule (molecular weight) increases, so does its electrons, which increases its polarizability, which causes the partial charges of the induced dipoles get larger, so the strength of the dispersion forces increase.
*pg108

Question 35

Phyical properties that get affected by intermolecular forces

Answer 35

No matter the strength all intermolecular forces impact physical changes. substances with stronger forces have higher melting and boiling points, greater viscosities, and lower vapour pressure than similar compounds with weaker forces.
*pg108

Question 36

van der Waal’s forces

Answer 36

collective term for dipole forces, H bonding, and London forces. Sometimes only used to say London forces though.
*pg108

Question 37

Hydrogen bonding

Answer 37

This is strongest type of intermolecular force bw neutral molecules. 2 rules for this to occur:
1. a molec must have a covalent bond bw H and either N, O, or F
2. another molecule must have a lone pair of electrons on an N, O, or F atom.
Water is one of the most common examples.
*pg109

Question 38

Consequences of H bonding

Answer 38

The boiling points of these compounds are very high.

*pg109

Question 39

Vapour pressure

Answer 39

The pressure exerted by the gaseous phase of liquid that evaporated from the exposed surface of the liquid. The weaker a substance’s intermolecular forces the higher the vapour pressure and the more easily it evaporates.
Vapour pressure is also temp dependent, and inc with temp of the substance. The reason for this is because inc the avg Kinetic energy of the particles lets them overcome the intermolecular forces.
Vapour pressure is indirectly related to its boiling point.
*pg109

Question 40

Volatile

Answer 40

Liquids with high vapour pressure

*pg109

Question 41

Ionic solids

Answer 41

Held together by the electrostatic attraction between cations and anions in a lattice structure. The bonds that hold all the ions together in the crystal lattice are the same as the bonds that hold each pair of ions together. Ionic bonds are strong and most ionic substances are solid.
The greater the charge the stronger the force of attraction bw the ions. The smaller the ions. the more they are attracted to each other.
*pg110

Question 42

Network solids

Answer 42

Atom are connected in a lattice of covalent bonds, meaning that all attractions between atoms are covalent bonds. Like in an ionic solid the intermolecular forces are identical to the intramolecular forces. You can think of these as one big molecule. These only contain intramolecular forces. These are very strong, and tend to be very hard solids. An example is diamond
*pg110

Question 43

Metallic solids

Answer 43

A covalently bound lattice of nuclei and their inner shell electrons, surrounded by a ‘sea’ or ‘cloud’ of electrons. At least one valence electron per atom is not bound to any one particular atom and is free to move throughout the lattice. These free electrons are called conduction electrons, this is why metals are excellent conductors of electricity and heat, and are malleable and ductile. These bonds vary widely in strength, but almost all metals are solid.
*pg111

Question 44

Molecular solids

Answer 44

The particles at the lattice points of a crystal of a molecular solid are molecules. These molecules are held together by one of 3 types of intermolecular interaction: H bonds, dipole, or London dispersion. These solids are much weaker than ionic, network, and metallic which is why they have much lower melting and boiling points. These are often liquids or gaseous, and are most likely to be solids as the strength of their forces increase.
*pg111