Unit 1

Question 1

Which are stronger Intermolecular or Intramolecular forces?

Answer 1

Intramolecular forces are physical and stronger

Question 2

What determines physical properties?

Answer 2

intermolecular forces determine physical properties

Question 3

How do intermolecular forces affect physical properties?

Answer 3

• More polar = higher boiling point
• More electrons = higher london dispersion forces
• Bigger molecule = higher LDF making it harder to break

Question 4

What does n, l, ml and ms mean?

Answer 4

• n: shell
• l: subshell
• ml: orbital
• ms: direction of spin

Question 5

What is the Pauli Exclusion principle?

Answer 5

No two electrons can have the same 4 quantum numbers + Electrons cannot spin the same direction in an orbital

Question 6

What is the Aufbau principle?

Answer 6

Electrons are added to the lowest possible energy orbital available in an atom or ion before being added to higher ones

Question 7

What is Hunds rule?

Answer 7

The positive electron occupies each orbital first before going back and filling the second electron space with a negative electron.

Question 8

Why do we emphasize the valence electrons in an atom when discussing atomic properties?

Answer 8

Valence electrons are responsible for properties like bonding

Question 9

What is the Anion rule for electron configuration?

Answer 9

Add the electrons needed
Ex. O: 1s2,2s2,2p4
O-2: 1s2,2s2,2p6

Question 10

What is the Cation rule for electron configuration?

Answer 10

Remove electrons from the orbital with the highest n value

Question 11

What are excited electrons?

Answer 11

electrons that have gained energy and have jumped to a higher energy orbital (total number of electrons stay the same)

Question 12

What is the formal charge?

Answer 12

hypothetical charge of an atom within a molecule

Question 13

What does isoelectric mean?

Answer 13

same number of electrons

Question 14

How does Quantum Theory explain ionic bonding?

Answer 14

Transfer of electrons from one orbital to another
(from the metal to the non-metal)

Question 15

How does the valence bond theory explain how covalent bonds are formed?

Answer 15

The model theorizes that a covalent bond forms when two orbitals overlap to produce a new combined orbital containing two electrons of opposite spin.

Question 16

Where is the shared electron pair most likely to be found?

Answer 16

The shared electron pair is most likely to be found in the space between the two nuclei of the atoms forming the bonds.

Question 17

Does orbital overlapping result in an increase or decrease in energy?

Answer 17

This overlapping results in a decrease in the energy of the atoms forming the bond. (having an orbital with only one electron is a higher energy state)

Question 18

What is hybridization?

Answer 18

Hybridization is the process of forming hybrid orbitals of at least two different orbitals (must be done for bonding)
- Creating a hybrid orbital where all the electrons are of the same energy level

Question 19

What is a sigma bond?

Answer 19

a bond created by the end-to-end overlap of atomic orbitals

Question 20

What is a pi bond?

Answer 20

a bond created by the side by side (or parallel) overlap of two un-hybridized p orbitals (one from each neighboring atom).

Question 21

what does a double bond contain? triple bond?

Answer 21

• double bond: 1 sigma 1 pi
• Triple bone: 1 sigma 2 pi
• both are partial hybridization

Question 22

What is an expanded octet?

Answer 22

An expanded octet is an exception to the octet rule where a central atom in a Lewis structure has more than eight electrons in its valence shell.
- For hybridized orbitals, must use d orbitals in the hybrids

Question 23

What is the VSEPR Theory?

Answer 23

A model used to predict the 3-dimensional geometry of molecules based on the repulsion of the bonding and non-bonding electrons in the molecule.

Question 24

What is the assumption in the VSEPR theory?

Answer 24

Atoms in a molecule are bound together by pairs of electrons 🡪 bonding pairs

Question 25

How do lone pairs position themselves on atoms in molecules?

Answer 25

- Pairs of electrons around any particular atom position themselves as far apart from each other as possible (as to minimize the repulsion between bonding and non-bonding pairs) - Lone pairs occupy slightly more space than bonding electron pairs (so they push bonding pairs away, decreasing their bond angle by 2.5°)

Question 26

How is shape of a molecule determined?

Answer 26

The shape is determined by the number of bonding and non-bonding electrons in the molecule. Lewis diagram must be drawn first.

Question 27

What is the difference between electron and molecular geometry?

Answer 27

- Electron geometry is the general shape of electron groups but is often not the shape of the molecule - Molecular geometry is the position of only the atoms in the molecule (not bonding pairs)

Question 28

What are vectors?

Answer 28

A vector is a bond dipole used to represent polar covalent bonds pointing towards the more electronegative atom. - to obtain final resultant vector, add vectors

Question 29

What are the 4 types of solids?

Answer 29

Ionic, metallic (metals cu), molecular (non-metals polar and non-polar), and covalent network (metalloids/carbon)

Question 30

What are ionic crystals made up of and it's properties?

Answer 30

- consisting of 3D arrangement of positive and negative ions in a crystal lattice structure - Hard but brittle (if struck, becomes distorted and repel) - high melting points (due to very strong electrostatic forces) - Soluble in water and conducts electricity in liquid (ions conduct better)

Question 31

What is the structure of metallic crystals?

Answer 31

- solids with closely packed atoms held together by electrostatic interactions and free moving electrons

Question 32

What is the electron sea model theory?

Answer 32

- states that the electrons in a metallic crystal move freely around the fixed positively charged nuclei

Question 33

What is metallic bonding?

Answer 33

bonding that holds the nuclei and electrons of metal together

Question 34

Why do metallic ions pack closely together?

Answer 34

Pack as close as possible because of strong electrostatic forces between the ions and the free moving electrons

Question 35

What are the properties of metallic crystals?

Answer 35

- Have low ionization energy and easily give up electrons - Sheen due to mobile valence electrons absorbing and emitting light - malleable due to the electron sea allowing electrons to slide over each other - Electrical conductivity due to free moving electrons (when metal is connected to a battery) - hardness due to the electron sea surrounding nuclei producing strong electrostatic attractions that hold nuclei together

Question 36

What are molecular crystals made of?

Answer 36

- composed of individual molecules held together by intermolecular forces - can be polar or non-polar

Question 37

What are the properties of molecular crystals?

Answer 37

- low melting point due to intermolecular interactions - little hardness due to intermolecular forces - bad with electrical conductivity when composed of non-polar molecules, some (not all) polar compounds when dissolved can ionize

Question 38

What are covalent network crystals?

Answer 38

atoms form covalent bonds in an interwoven network (ex. diamond, graphite, silicon carbide)

Question 39

What are the properties of covalent network crystals?

Answer 39

- Very high melting points - Extreme hardness - insoluble - not good conductors of electricity

Question 40

Compare diamond and graphite

Answer 40

- diamonds: huge network of C-C linkage (all 4 carbon bonds are equal in strength) - Graphite: carbons only use 3 electrons to bond with adjacent carbons - has a layer of carbon that isn't bonded - unused electrons can move freely (explains why graphite can conduct electricity) - layers are held together by weak LDF + can slip over each other (weak in 3D but strong in 2D)

Question 41

Compare glass and quartz

Answer 41

- have the same chemical formula but glass lacks long-range, regular crystalline structure of quartz making it weak

Question 42

What is the science behind bullet-proof fabrics (Kevlar)?

Answer 42

- The principle behind these fabrics is that impact energy is spread across many fibres, which deform and absorb the energy instead of letting the projectile penetrate deeply. - molecules are arranged in long chains with strong hydrogen bonding between chains creating crystalline structure.

Question 43

Advantage and Disadvantage of bullet-proof vest?

Answer 43

- multi-use for personal protection, recreational use (sports gloves and equipment) , industrial use (aerospace material) - non-biodegradable and involves harsh chemicals such as concentrated sulfuric acid

Question 44

How are lasers based on quantum theory?

Answer 44

Lasers work by exciting electrons with photons of specific energy, which then release identical photons when returning to lower energy levels. These photons amplify through collisions and reflections inside the ruby rod, producing a concentrated beam of parallel light waves that exit through a partially reflective mirror.

Question 45

What is the Bose-Einstein condensate?

Answer 45

Bose–Einstein condensate (BEC) is a state of matter that consists of a pile of atoms all in the same place at the same time and exists only at temperatures within a few billionths of a degree of absolute zero, which is 0 K or −273.15 °C.

Question 46

How do MRI work?

Answer 46

uses a strong magnetic field to cause the magnetic fields of the hydrogen atoms to align in the same direction as the outside magnetic field.