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Chemistry SL > Unit 2 > Flashcards

Unit 2 Flashcards

1
Q

What is Dalton’s model of an atom?

A
  • Composed of particles called atoms
  • Cannot be destroyed or created
  • Atoms of the same elements are identical
  • Atoms of different elements combine in small numbers to form molecules
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2
Q

What are electrons?

A
  • Different metals produce a stream of negatively charged particles when voltage is high
  • Displayed negative electrons suspended in positively charged substances
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3
Q

What are features of a nucleus?

A
  • Atoms are mainly space
  • Nucleus contained most of the mass of atom
  • Electrons surround the nucleus
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4
Q

What are subatomic particles?

A

Nucleus contains subatomic particles called protons, neutrons and most mass of atom, electrons occupy space outside of nucleus.

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5
Q

What are ions?

A

Atoms lose or gain electrons to form ions

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6
Q

What are cations?

A

Positive ions formed by loss of one or more electrons

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7
Q

What are anions

A

Negative ions formed by gain of one or more electrons

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8
Q

What are isotopes and its properties?

A

Isotopes are elements with the same number of protons but different number of neutrons. They have:
- Same chemical properties as parent element since neutrons don’t affect how they react
- Isotopes with more neutrons heavier and slower
- Difference in neutrons affects physical properties such as boiling, melting points, density and rate of diffusion

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9
Q

What is the use of carbon 12?

A

Since masses of elements range, difficult to manage using relative values thus standard agreed upon.
Carbon 12 chosen as relative mass exactly 12g, thus other elements measured relative to Carbon 12 isotope.

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10
Q

What are atoms?

A

Smallest particles that retain of the element, they have nucleus and space around nucleus where electrons are located

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11
Q

What is a electromagnetic spectrum?

A

The electromagnetic spectrum is a range of frequencies that covers all electromagnetic radiation and their respective wavelengths and energy
It is divided into bands or regions, and is very important in analytical chemistry.
The spectrum shows the relationship between frequency, wavelength and energy2

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12
Q

What is emission spectrum?

A

When electrons energy increases, electrons jump to a higher level but can also be reversible and return to original energy levels results in frequency being same but as its emitted and not absorbed
Energy emitted is mixture of different frequencies which corresponds to possibility of electron jumps between energy shells.

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13
Q

What is continuous spectrum?

A

A continuous spectrum in the visible region contains all the colors of the spectrum
This is what you are seeing in a rainbow, which is formed by the refraction of white light through a prism or water droplets in rain

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14
Q

What is line spectrum?

A

a line spectrum only shows certain frequencies, This tells us that the emitted light from atoms can only be certain fixed frequencies with each line representing a specific energy level

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15
Q

What is the hydrogen spectrum?

A

Hydrogen atoms give out energy when electrons falls from higher to lower energy levels
Hydrogen produces visible light when electrons falls to second energy level

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16
Q

What region is n=1 level?

A

UV region

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17
Q

What regions is n=2 level?

A

Visible light

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18
Q

What region is n=3 level?

A

Infrared

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19
Q

What are rules and principles of electronic configurations?

A
  • Electrons enter lowest available energy level
  • 2 electrons in each orbital, providing they are opposite spin
  • Placing 2 electrons in one orbitals means both negatively charged, thus electrostatic combustions present which places electrons on separate orbital reducing repulsion and system become more stable.
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20
Q

What are properties of shells?

A

Electrons are arranged in electron shells with shells having sub shells. Each shell made up of electron orbitals each holding 2 electrons.

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21
Q

What are properties of orbitals?

A

Each level consist of electron orbitals, each holding 2 electrons with opposite spin. Orbitals are regions of space that electrons are most likely to be in.

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22
Q

What is afbau principle and level of energy shells?

A

When electrons enter orbital at lowest energy orbital available, Order is as follows: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4d etc

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23
Q

What is hund’s rule for electron orbitals?

A

Electrons occupy orbitals on own, they only pair up when no empty orbitals of the same energy available. Arrows represent opposite spins and are in up or down direction.

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24
Q

How are ions formed?

A

Ionic bonds involve transfer of electrons from metal to non metal, transferring electrons leaves metal and non metal with full outer shell

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25
Q

What is ionic bonding?

A

Forces of attraction between oppositely charged ions, cations and anions oppositely charged thus attract each other and forms ionic compounds, forms of attract very strong and requires lots of energy to overcome.

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26
Q

What are binary ionic compounds?

A

Composed of ions of 2 different element, consists of cation and anion.
Ex: Sodium Iodide

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27
Q

What are the charges of ionic compounds?

A

They are electrically neutral as positive charges equal negative charges meaning overall change is zero

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28
Q

What are charges of positive metal ions?

A
  • Metals form positive ions
  • Metals in group 1, 2 and 3 have charge of 1+, 2+ and 3+
  • Charge on transition elements shown through roman numerals
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29
Q

What are charges of negative nonmetal ions?

A
  • Non metals in group 6 to 8 have negative charge and suffix ide, elements in group 6, 7, 8 have charges 1-, 2- and 3-
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30
Q

What are polyatomic ions?

A

Negative compounds ions made up of more than one type of atom, generally negative but can be positive

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31
Q

What are the seven polyatomic ions?

A
  • Ammonium (NH4+)
  • Hydroxide (OH-)
  • Nitrate (NO3-)
  • Hydrogen carbonate (HCO3-)
  • Carbonate (CO3 2-)
  • Sulfate (SO4 2-)
  • Phosphate (PO4 3-)
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32
Q

How does nuclear charge work?

A
  • Increases as you move across periodic table
  • Nuclear charge of outer electrons less than full nuclear charge
  • Effective charge increases with nuclear charge as no change in inner electrons
  • As you go down the group, effective charge stays the same
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33
Q

How do ionization energies work for elements in periodic table?

A

Elements with lower ionization energies form positive ions, ionization decreases down the group.

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34
Q

What are ionic lattices?

A

Ionic compounds form ionic lattices, evenly distributed crystalline structures.
Ions in lattice arranged in regular pattern so that positive charges cancel out negative charges.
They are arranged in repeating pattern.

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35
Q

What forces hold ionic lattices together?

A

Consists of alternating cations and anions thus electrostatic forces of attraction between oppositely charged ions.

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36
Q

What is lattice enthalpy?

A

Lattice dissociation enthalpy is standard enthalpy change that occurs on formation of 1 mole of gaseous ions from solid lattice, endothermic process so enthalpy change will be positive value.

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37
Q

What are properties of ionic compounds (Melting point, volatility, solubility, conductive) ?

A
  • Strong electrostatic forces in ionic compound keeping ions together
  • Brittle as ionic compounds can split apart
  • High melting and boiling point due to electrostatic attractions in all directions to keep strongly together
  • Not volatile, lots of energy needed to overcome strong electrostatic attractions
  • Soluble in water as they form ion dipole bonds
  • Conducts electricity when molten or in solutions as ions freely move, cannot in solid as electrons in fixed position and cannot move.
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38
Q

What are covalent bonds?

A
  • Bonding between 2 non metals, involves electrostatic attractions between 2 nuclei at 2 atoms and electrons of their outer shells.
  • Electrons only shared in types of bonding where 2 atomic orbitals and molecular orbitals formed
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39
Q

Why does covalent bonding occur?

A

Electrons become more stable when attracted to 2 nuclei compared to only one and when elements have full outer shell.

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40
Q

How does the formation of covalent bonds happen in hydrogen molecules?

A
  • Each atom provides one of the bonds represented by short straight lines between 2 atoms, covalent bonds in constant motion and best regarded as charge clouds.
41
Q

How do the representation of electron charge clouds work?

A
  • Allows each of the atoms to have full electron configurations.
42
Q

What happens when electrons don’t have full outer shell

A

central atom of covalent molecule accommodates more or less than 8 electrons in outer shell, this is called electron deficiency.

43
Q

What are lewis formulas?

A

Simplified electron shell diagrams shows pairs of electrons around atoms and represented by dots, crosses and combinations of both or by a line.

44
Q

What are steps to draw a lewis formula?

A
  1. Count no. of valence electrons
  2. Draw skeletal structure to show how many atoms linked to each other
  3. Use crosses to put electron pair in each bond of atoms
  4. Add electron pairs to complete octets around atoms
  5. Form double / triple bonds if not enough
  6. Check total no. of electrons to see if equal to total no. of valence electrons
45
Q

What happens to elements with incomplete octets?

A

Elements below atom no. 20 aims to achieve 8 electrons in valence shells to have same electronic configuration as noble shells.

46
Q

What are exceptions to the octet rule?

A
  • Hydrogen and Lithium can have 2 in outer shell
  • Be forms stable compound with 4 valence electrons
  • B and Al forms stable compound with 6 valence electrons
  • S and P can hold more than 8 electrons
47
Q

What are multiple bonds?

A

Non metals able to share more than one pair of electrons to form covalent bonds, allows each of 2 atoms to achieve full electron configuration.

48
Q

How many covalent bonds can be shared?

A

Only two or three bonds, unable to form quad bonds as repulsion from having 8 electrons in same region between 2 nuclei too great.

49
Q

What is bond energy?

A

Energy required to break one mole of particular covalent bond in gaseous states, larger the bond the strong the covalent bond is.

50
Q

What is bond length?

A

Distance from nucleus of one atom to another atom forming covalent bonds.
- greater forces of attraction between electrons and nuclei, the more atoms pulled closer to each other causing bond length of molecule to decrease and strength of covalent bond to increase

51
Q

What is diamond?

A

Giant lattice of carbon atoms , each carbon covalently bonded to 4 others in tetrahedral arrangement with bond angle of 109.5 degrees, many strong covalent bonds that are needed to be broken down.

52
Q

What are the properties of diamond?

A
  • Hardest substance known, used for drills and glass cutting
  • High melting / boiling point
  • Not electrically conductive
  • Good thermal conductor
53
Q

What is graphite?

A

Each carbon atom bonded to 3 others in layered structure, layers made of hexagons with bond angle of 120 degrees. Spare electron is delocalized and occupies space in between layers with all atoms held by strong covalent bonds but with weak intermolecular forces between layers.

54
Q

What are the properties of graphite?

A
  • Soft and slippery
  • good electrical and thermal conductivity
  • Used in pencils, lubricants, batteries.
  • High melting / boiling point as they appear as grey solid
55
Q

What is buckminsterfullerene (C60) ?

A

Type of fullerene, contains 60 carbon atoms each bonded to three others by single covalent bonds thus having weak intermolecular forces of attractions between molecules. 4th electron is delocalized so electrons can migrate throughout structure

56
Q

What are properties of buckminsisterfullerene?

A
  • Same shape as football
  • Poor electrical and thermal conductivity
  • Light and strong
  • appear as black powder
  • High melting / boiling point but small amounts of heat energy needed to overcome bonds
  • Used for gene and drug delivery within body
57
Q

What is graphene?

A

Single layer of carbon atoms bonded together with 3 strong covalent bonds per atom in repeating pattern of hexagons, some substances contain lattice of covalently bonded atoms in 2 dimensions to form layers.

58
Q

Properties of graphene?

A
  • Thinnest and strongest material
  • Very good electrical and thermal conductivity
  • Appear as transparent
  • High melting / boiling point
  • Used for solar cells or batteries.
59
Q

What is silicon?

A

Silicon atoms in silicon are in tetrahedra arrangement with each silicon atom covalently bonded to 4 other silicon atoms with giant lattice structure

60
Q

Properties of silicon?

A
  • Poor electrical conductivity but good thermal conductivity
  • High melting and boiling point and appear as grey white solid
  • Used for construction, electronics
61
Q

What is silicon oxide?

A

Known as silicon dioxide has same structure as diamond with tetrahedral units bonded by strong covalent bonds, each silicon shared by 4 oxygens shared by two silicon atoms

62
Q

Properties of silicon oxide?

A
  • Very high melting / boiling point
  • Appears as transparent crystals
  • Non electrical conductors but good thermal conductivity
  • Used to produce concrete and glass.
63
Q

What are coordinate bonds?

A

Simple covalent bonds have 2 atoms involved with share electrons, some molecules have lone pair of electrons donated to form electron deficient atom thus forming same atom.

64
Q

What is the valence shell electron pair repulsion (VSFER) theory?

A

VSFER theory is when electrons form covalent bonds with other atoms, electrons in different bonds in outer shell behave as negatively charged clouds and repel each other. Thus valence electrons spread out as far as possible.

65
Q

What are three basic rules of VSFER theory?

A
  • All electrons pairs and lone pairs arrange themselves as far as possible
  • Lone pairs repel more strongly than bonding pairs
  • Multiple bonds behave like single bonds
66
Q

What are 2 electron domains?

A
  • If 2 electron domain on central atom, bond angle is 180 degrees
  • Molecules known as molecular geometry linear
  • Examples: BeCL2 / CO2
67
Q

What are 3 electron domains?

A
  • If 3 electron domain on central atom, bond angle is 120 degrees
  • Molecules are molecular geometry trigonal planar shapes
  • Examples: BF3 / CH20
68
Q

What are 3 electron domains but one lone pair?

A
  • If one of these electrons have lone pair, bond angle less due to stronger repulsion from lone pairs forcing bonds closer together
  • Bond angle is 117-118 degrees
  • Known as molecular geometry bent
  • Example: Sulfur dioxide
69
Q

What are 4 electron domains?

A
  • 4 electron domain on central atom than bond angle is 109.5 degrees
  • Molecules are molecular geometry tetrahedral shape
70
Q

What are 4 electron domains but with one lone pair?

A
  • If one electron domain is lone pair, bond angle is 107 degrees due to extra lone pair repulsion forcing bonds closer together
  • Molecules which adopt these shape are molecular geometry trigonal pyramid.
71
Q

What are 4 electron domains but with 2 lone pairs

A
  • If 2 electron domains lone pairs, bond angle is 104.5 degrees due to extra lone pair repulsion
  • Molecules known as molecular geometry bent linear
72
Q

What are forces of attraction and how it works in ionic and covalent compounds?

A

Forces that hold atom together which are between positive and negative charges
- Ionic: Transfer of electrons between metals and non metals
- Covalent: Electrons shared between 2 atoms

73
Q

What is electronegativity?

A

Power of atom to attract electron density of covalent bond,

74
Q

What is electron density?

A

Used to describe way charge is distributed when considering electrons as clouds of charges

75
Q

What are polar bonds?

A

2 atoms in covalent bond have different electronegativities, this means bond is polar and electrons drawn towards more negative atom

76
Q

What are the results of polar bonds?

A
  • Negative charge center and positive charge center not coinciding
  • Electron distribution is asymmetric.
  • Less electronegative atom is delta positive partial charge
  • More electronegative atom is delta negative partial charge
77
Q

What is the extent of polarity?

A

Covalent bonds vary depending on how big different in electronegativity values of 2 bonded atoms, bigger the difference = bigger the polarity

78
Q

What is dipole?

A

Measures how polar a bond is, direction of dipole movement shown by arrow pointing towards negatively charged end of the dipole.

79
Q

What are forces affecting electronegativity?

A
  • Nuclear charge of atom
  • Distance between nucleus and outer electrons
  • Shielding of nuclear charge by electrons in inner shells
80
Q

What are partial charges?

A
  • If 2 atoms that are bonded together have different electronegativity, represents partial charge and shown as delta positive or negative.
81
Q

What is symmetry?

A

When molecules symmetrical, no overall polarity and electron cloud shared evenly over whole molecule.

82
Q

How to determine whether molecule is polar?

A
  • Polarity of each bond in molecule
  • How bonds arranged in molecules
  • Some molecules have polar bonds but not polar overall because polar bonds in molecules arranged in which individual diploe cancels each other out.
83
Q

What are dipole dipole forces?

A
  • Temporary dipole exists in all molecules but some are molecules with permanent dipole attracted to each other. This is attraction between permanent dipole on one molecule and permanent on other.
  • Dipole dipole results in boiling point to be slightly higher than expected thus increasing strength of intermolecular attractions
83
Q

What are trends of intermolecular forces?

A
  • As you go down the group, valence shell further away from nucleus thus temporary dipole caused by electron distortion
  • Solids have highest IMF of attraction, then liquid then gas
  • Increase in boiling point as size of molecule increases due to greater electron density leading to higher IMF.
  • Large surface area = more contact with adjacent molecules thus higher melting / boiling point.
84
Q

What are the properties of hydrogen bonding to work?

A
  • Strongest type of IMF, special type of permanent dipole dipole bonding
  • Requires hydrogen to be bonded to O, N or F with lone pair of electrons leading to very highly polarized.
  • Hydrogen becomes delta positive when hydrogen bonding occurs
85
Q

How does London dispersion forces work?

A

Electrons not static but in constant motion, thus electrons not symmetrical with surplus of atoms on one side.
- Temporary induced dipoles constantly appearing and disappearing as electrons constantly moving
- Occur between all atoms but very weak and all reason all compounds liquid or solid
- Strength of forces dependent on no. of electrons and surface area.

86
Q

Trends with london dispersion forces for no. of electrons?

A
  • More no. of electrons, greater chance of distortion greater frequency and magnitude of temporary dipoles
  • Dispersion forces between molecules stronger and melting / boiling point higher
87
Q

Physical properties for melting and boiling point?

A
  • When covalent structures change, IMF overcome with strong the forces needed, more energy needed to break attractions
  • IMF weaker than covalent bond, thus covalent substances mainly liquid or gas at room temp
  • Low boiling / boiling point = Not volatile
  • Strength of IMF increases with size of molecule, increase in polarity and higher molecular formula
88
Q

Physical properties for solubility?

A
  • Non polar structures dissolve in non polar solvents as they form VDW forces between solvent and solute
  • Polar substances dissolve in polar solvent due to dipole-dipole interactions or hydrogen bonds between solute and solvent
  • Large covalent molecules = lower solubility as polar part of molecule is small part of overall structure
  • Polar substances unable to dissolve well in non polar solvents as dipole dipole attractions unable to interact with solvent
89
Q

Physical properties for solubility?

A
  • As covalent bonds don’t contain freely moving particles, unable to conduct electricity in solid or liquid.
  • Certain conditions allow polar covalent to conduct due to delocalized electrons.
90
Q

Physical properties of non polar covalent substances (boiling point/volatility/solubility/conductivity) ?

A

Melting / Boiling point = Low
Volatiltiy = Highest
Solubility in polar solvents = Insoluble
Solubility in non polar solvents = Soluble
Electrical conductivity = None

91
Q

Physical properties of polar covalent substances (boiling point/volatility/solubility/conductivity) ?

A

Melting / Boiling point = Low
Volatiltiy = High
Solubility in polar solvents = Some soluble
Solubility in non polar solvents = Some Soluble
Electrical conductivity = None

92
Q

Physical properties of giant covalent substances (boiling point/volatility/solubility/conductivity) ?

A

Melting / Boiling point = Very High
Volatiltiy = Low
Solubility in polar solvents = Insoluble
Solubility in non polar solvents = None
Electrical conductivity = None except graphite/graphene

93
Q

Physical properties of ionic substances (boiling point/volatility/solubility/conductivity) ?

A

Melting / Boiling point = Very High
Volatiltiy = Low
Solubility in polar solvents = Soluble
Solubility in non polar solvents = Insoluble
Electrical conductivity = Only when molten or aqueous.

94
Q

How does concept of ionization energy work from line spectrums?

A

In spectrum, lines get closer together at higher energy end as electron reaches maximum amount of energy. This corresponds to ionization energy of electron. We know that lines corresponds to electrons jumping from higher levels down to n=2.

95
Q

What are orbitals?

A

Subshells containing one or more atomic orbital that exist at specific energy levels with electron being found on one of these levels.

96
Q

What are shapes of s orbitals?

A

Spherical in shape with size of s orbital increases with increasing shell number. Ex: 3s larger than 1s.

97
Q
A

Chemistry SL (6 decks)

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