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AA IB Chemistry HL > Structure 3.1 > Flashcards

Structure 3.1 Flashcards

1
Q

What is the atomic radius?

A

1/2 the distance between the nuclei of two bonded atoms

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2
Q

What is the trend in atomic radius down the group?

A

Increases due to increasing energy levels, electrons further away from the nucleus
Same shielding

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3
Q

What is the trend in atomic radius across a period?

A

decreases
same energy level and shielding
increase in nuclear charge

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4
Q

What is electron affinity?

A

the energy released when 1mol of electrons is attached to 1 mol of neutral atoms or molecules in the gas phase
always negative, as atoms lose energy in the exothermic process of adding an electron

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5
Q

The greater the electron affinity…

A

the more negative it is, the greater is the attraction of the ion for the electron

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6
Q

Three factors that explain the trends are:

A
  1. attractive force of nucleus for the valence electrons - number of protons
  2. in which energy level the valence electrons are
  3. shielding of nuclear attraction by electrons
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7
Q

What is the general atomic radius trend?

A

down a group - increases
across a period - decreases

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8
Q

What is the general ionisation energy trend?

A

down a group - decreases
across a period - increases

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9
Q

What is the general electronegativity trend?

A

down a group - decreasing
across a period - increasing

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10
Q

What is the general electron affinity trend?

A

down a group - decreases
across a period - increases

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11
Q

What is the comparison between the size of cations and anions?

A

cations are smaller than anions, the opposite being true only for extremities of the periodic table

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12
Q

What is ionisation energy?

A

Ionisation energy is the energy required to remove the outermost electron from a species

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13
Q

What is (specifically) the 1st ionisation energy?

A

the minimum energy required to lose one mole of electrons from one mole of gaseous atoms in the ground state

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14
Q

What is the trend in 1st ionisation energy down a group?

A

Decreases:
Atomic radii increases, electrons occupy higher energy levels
Leads to a weaker attraction to the nucleus
Less energy required to remove an electron

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15
Q

What is the trend in 1st ionisation energy across a period?

A

Increases:
Nuclear charge increases (there are more protons) and the atomic radius decreases
More energy is required to remove an electron

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16
Q

What does the trend in ionisation energy across a period depend on?

A

nuclear charge and atomic radius
the greater the nuclear charge and the smaller the atomic radius, the higher the ionisation energy

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17
Q

What is electron affinity?

A

amount of energy released when a neutral atom gains an electron to form a negatively charged ion

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18
Q

What is the general trend in electron affinity going down a group?

A

Decreases going down a group
Elements increase their atomic radius, and outer valence shells are further away from the nucleus
Weaker attraction between the added electron and the nucleus

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19
Q

What is the general trend in electron affinity going across a period?

A

increases
Elements across the period have a higher effective nuclear charge
Stronger attraction between the added electron and the nucleus

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20
Q

What is electronegativity?

A

the tendency of an atom to attract a shared pair of electrons in a covalent bond

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21
Q

What is the general trend in electronegativity going down a group?

A

decrease down a group
atomic radius increases due to additional energy levels
Weaker attraction between the nucleus and the shared pair of electrons

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22
Q

What is the general trend in electronegativity going across a period?

A

increase
Effective nuclear charge increases
Stronger attraction between the nucleus and the shared pair of electrons

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23
Q

What is metallic and non-metallic character?

A

metallic: the tendency of an element to lose electrons to form positive ions, lower ionisation energy
non-metallic: tendency of an element to gain electrons, higher electron affinity

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24
Q

What is the general trend of reactivity for group 1 metals with water?

A

Increasing reactivity going down group 1
Elements have lower 1st ionisation energies, due to an additional energy level
Easier for with lower ionisation energy to transfer the outer valence electron to water increasing reactivity with water.

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25
What are the halogens?
non-metallic elements in group 17 that exist as diatomic molecules highly reactive since they have a tendency to gain electrons
26
What is the relationship between electron affinity and reactivity?
as electron affinity decreases, so does reactivity
27
What is a spectator ion?
Aqueous ions that remain unchanged throughout a chemical reaction
28
What is amphoteric?
means that a substance has the ability to act as either an acid or a base depending on the surrounding environment
29
What are the period 3 oxides acid-base character?
goes from basic metal oxides to acidic non-metal oxides as you move across the period
30
What is the acid/base nature of oxides at the cusp of the bonding triangle (between ionic and covalent)?
may be amphoteric
31
What is formed when a non-metal oxide reacts with water?
an acid
32
What is formed when a metal oxide reacts with water?
metal hydroxide is formed, basic
33
What is ocean acidification and its impacts?
CO2 can dissolve in bodies of water, acidifying it as H2CO3 is formed - marine organisms have difficulty adapting to minor pH changes - marine food chains and storm protection from reefs are negatively impacted
34
What is acid rain?
Sulfur and nitrogen containing oxides produce H2SO4 and HNO3 when they react with water
35
What are the environmental impacts of acid rain?
impacting crop yields damaging infrastructure impacting tree growth negatively impacting the respiratory systems of mammals
36
What is an oxidation state?
a number assigned to an element showing the number of electrons lost/gained/shared in a compound or ion
37
What determines the oxidation number?
the relative electronegativities of elements
38
What is the difference between an oxidation state and an ionic charge?
Oxidation states - hypothetical, a method to track how electrons are distributed, electron transfer may not have occurred at all Ionic charges - numerical quantity of electrons that has been lost/gained
39
What are the different notations for ionic charge and oxidation state?
Ionic - 1+ Oxidation - +1
40
What are the main rules for assigning oxidation states?
1. a pure element will have an oxidation state of 0, due to the same tendency to attract or gain electrons 2. monoatomic ions have an oxidation state equal to the ionic charge 3. oxidation state in a neutral compound sum to 0 4. oxidation states in polyatomic ions add to sum of ionic charge 5. oxidation numbers are usually the charge of the most common ion 6. assign positive oxidation numbers first to most/least metallic elements, on the outside of the formula
41
Where are the discontinuities in the trend in 1st ionisation energy?
between groups 2 and 3 between groups 5 and 6
42
Why is there a discontinuity in 1st ionisation energy between groups 2 and 3?
group 2 elements - outer electron occupies an s sublevel group 3 elements - outer electron occupies a p sublevel p sublevel has a higher energy so the nucleus has a weaker attraction to it
43
What do the discontinuities in the 1st ionisation energy suggest?
group 3 and 6 elements have a weaker attraction between nucleus and valence electrons than expected (given their higher ENC than groups 2 and 5)
44
What does the discontinuity between group 2 and 3 in the 1st ionisation energy prove?
the existence of a sublevel that is slightly higher in energy for the placement of a 3rd electron
45
Why is there a discontinuity in 1st ionisation energy between groups 5 and 6?
group 5 - valence electrons occupy p sublevel singly group 6 - one double occupancy in the p sublevel increased electron electron repulsion decreases attraction between valence electron and nucleus
46
What does the discontinuity between group 5 and 6 in the 1st ionisation energy prove?
the existence of orbitals able to hold a maximum of two electrons that make up each sublevel
47
What is a transition element?
an element with an incomplete d-sublevel that is able to form cations with an incomplete d-subshell
48
Why are transition elements called transition?
they exhibit transitional behaviour acting as somewhere between s-block metals and p-block non-metals
49
What is the main determiner of transition element's properties?
their incomplete d-sublevels
50
What are 6 characteristic properties of transition elements?
1. variable oxidation states 2. high melting points 3. magnetic properties 4. catalytic properties 5. form coloured compounds 6. form complex ions
51
Why do transition elements have variable oxidation states?
valence electrons occupy both s and d sublevels, so electron loss can occur from d sublevel after s sublevel loss variable number of electrons that can be removed
52
Why do transition elements have high m.p?
form ions with varying oxidation states, leads to many delocalised electrons in the 'sea'' increases strength of the metallic bond
53
Why do transition elements have high magnetic properties?
sublevels with unpaired electrons can show magnetism
54
What is and what causes ferromagnetism?
it is a strong interaction with a magnetic field when some transition metals form a metallic lattice structure with a long range alignment of unpaired electrons
55
Why do transition elements have catalytic properties?
provide a surface for the reaction to occur and ions to lose/gain electrons ions of transition elements react with one reactant to increase its oxidation state, then reacting with the other reactant to return to its original oxidation state. the two reactants have either gained/lost electrons and can easily react now
56
What is a catalyst?
a substance that changes the rate of a reaction and is not used up nor changed by the reaction
57
Why do transition elements form coloured compounds?
vary depending on transition element, oxidation state, other species in the compound...
58
Why do transition elements form complex ions?
transition metal ions bond to other substances lone pairs on ligands are attracted to the positively charged transition element and form a coordination bond
59
What is a ligand?
in a complex ion, a ligand is the surround species that donates a lone pair of electrons, forming a coordinate bond with a transition metal ion
60
What is the requirement for something to be a ligand?
it must have a lone pair of electrons on at least one atom in a molecule
61
What is necessary for a ligand to form multiple coordinate bonds with the transition metal ion?
it must have more than 1 lone pair available
62
Are electrons first lost from the s or d sublevel?
first from the outer s, then the outer d
63
What is successive ionisation?
the process of removing successive electrons from an atom or cation
64
Explain in more detail why transition elements have variable oxidation states.
4s and 3d-sublevels are close in energy Electrons are lost first from the 4s-, but can also be lost from the 3d-sublevel without applying much additional energy there are a number of d electrons that can be lost in addition to s electrons
65
How are complex ions formed?
when ligands form coordinate bonds to the transition metal ion by donating a lone pair
66
What happens as the ligand approaches the transition metal?
the electrons from the ligand will be closer to the electrons in some d-orbitals and further from others the electrons in the d orbitals repel the lone pair electrons, causing a split in the d sublevel
67
What causes dd splitting?
- as ligands approach a transition metal ion, the electrons in the d-orbitals repel the lone pair electrons - causes the d level to split in energy - orbitals that are closer to the ligands become higher in energy due to this repulsion, remaining orbitals become slightly lower in energy
68
What happens after dd splitting?
electrons occupying d orbitals in the lower level are able to absorb energy and transition to the higher level
69
How is visible light formed from dd splitting?
difference in energy of the splitting of the d-sublevel links to the energy from photons of visible light
70
What happens when a solution containing a transition metal complex encounters visible light photons?
electrons in the lower d-sublevel absorb specific wavelengths of visible light the remainder, non absorbed, wavelengths of visible light are transmitted through the solution
71
Why are different colours formed in different transition element complexes?
slightly different energies between the split d sublevel resuls in visible light of a different wavelength absorbed for each complex
72
What happens when a colour is absorbed?
we observe the transmitted light as the complementary colour
73
Which equations relate the energy of dd splitting to the frequency/wavelength of light ABSORBED?
E = hf c = f*wavelength
74
What is spectrophotometry and colorimetry?
Technique to quantify concentration of transition metal ions in solution
75
What 2 techniques can be used to find out the concentration of transition metal ions in solution?
spectrophotometry colorimetry
76
What is the relative size of cations/anions?
cations - smaller than parent ions anions - larger than parent ions

AA IB Chemistry HL (9 decks)

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