3.1 Flashcards
principle quantum number
The principal quantum number (n) tells you the energy level or shell number where the electron is.
Atomic radius definition + trend
Atomic radius is the distance from the nucleus of an atom to the outermost electron shell.
- Decreases across periods: Additional proton -> higher nuclear charge -> greater attraction between electrons and nucleus causing radius to become smaller
- Increases down groups -> Valence electrons are added to a higher energy level -> presence of additional shell shields the electrons from the attractive electrostatic froce of the nucleus ->** Low effective nuclear charge **
Effective nuclear charge
Diminished electrostatic force experienced by a shielded valence electron - Zeff
Ionic radius trend for cations + examples of groups
Cations have more protons than electrons, increasing the nuclear electrostatic force of attraction so ionic radius is smaller than atomic radius - Group 1,2 13
Ionic radius trend for anions
and how can this increase further?
Anions: More electrons than protons so force of attraction between nucleus and the additional electrons is smaller so ionic radius is greater than atomic radius
the greater the magnitude of charge, the greater the atomic radius
Ionic radius general
Increases down the group
Decreases across period
Ionization energy def + equation
Minimum energy required to eject an electron out of a neutral atom or molecule in its ground state
x + IE = X (+1) + e-
IE trend
Generally decreases down groups due to greater shielding effect, less energy required to **ionize atoms. **
Across a period increases as protons increase so outermost electrons held closer to the nucleus due to increased nuclear charge. **At the same time shielding effect remains nearly constant **
Electron affinity definition + equation
Energy released when an additional electron is attached to a neutral atom or molecule
X + e- = X- + EA
Electron affinity trend + PREDICTION
Trend for first electron affinity is like ionization energy,
nuclear charge increases across a period and so more energy is released when an electron is added
ONLY GROUP 1 ELEMENTS: Electron affinity decreases down the group due to shielding
electron affinity decreasing down a group +examples
& why cant the data be accurate sometimes
Sometimes it drops cuz adding an electron might result in a less stable electron config (silicon and phosphorus)
+ not always accurate data (like for metals) cuz adding an electron is not favourable
electronegativity definition
atoms ability to attract a pair of electrons from a chemical bond to itself
electronegativity trend & why
decreases down groups and increases across periods
smaller atoms with nearly complete valence shells will attract electrons more easily than larger atoms with fewer valence electrons
metallic character trend and why
linked to ionization energy
decreases across the period
increases down groups
high metallic character have delocalized electrons so usually have low ionization energies
bronsted lowry acids and bases
acid: donates protons H+
base: accepts protons H+
reaction of metal and water & how do they increase
X + H20 = 1/2H2 + XOH
more vigorous going down the grp cuz metallic character increases
Lewis acids and bases
Lewis acids: accept electron pairs
Bases: Donate electron pair
halide ions + halogens reactions occurs when
and increases when
occurs when more electronegative element can oxidize the lesser electronegative element
increases with greater difference in electronegativity between reacting species
F2 reacts faster with I than CL
How do oxides change across periods
More acidic, less basic
Metallic / non metallic oxides in terms of lewis and what do they do
metallic oxides: lewis bases, donate electron pair
MgO + H20 = Mg(OH)2
non metallic oxides: lewis acids, accept electron pair
CO2 + H2O = H2CO3
Amphoteric def + example of equations
Behaves as both a lewis acid and base like Al203
AL203 + 2NaOH = 2Na(Al(OH)4) + 3H20
Al203 + 6HCL = 2ALCl3 + 3H20
why is rainwater naturally acidic + equation
presence of dissolved carbon dioxide forms weak carbonic acid
C02 + H20 = H2C03
reactions for n02 and how does nitrous acid become nitric acid
nitrogen dioxide + h20 = HN03 + HN02 (nitrous acid)
Nitrous acid oxidized by atmospheric oxygen
2HN02 + 02 = 2HN03
Typical pH value for rain and when do we say its acid rain and why does it occur
typically 5.6
Its acid rain when below 5.6 which occurs due to nitrogen and sulfur dissolving in the air
Sulfur Dioxide and Nitrogen dioxides come from?
- Naturally: volcanic eruptions and decomposing vegetation
- Industrial processes: combustion of fossil fuels with high levels of sulfur impururities
reactions for s02 and how does sulfurous acid become sulfuric acid
S02 + H20 = H2S03
Sulfurous acid is oxidized to form sulfuric acid
2H2S03 + 2H2S04
Why & how is the ocean affected by carbonic acid
It absorbs a lot of c02 released into the air which forms carbonic acid.
This affects the ability of coral reefs and shellfish to calcify their skeletons
oxidation state represents
charge on atom in compound
describes electrons shared or transferred when forming a bond
Important rules for oxidation states
Oxidation state of fluorine is -1 in all compounds
Oxidation of group 1/2 metals is always +1 / +2
oxidation state of oxygen is always, except….
Oxidation state of oxygen is -2
except OF2
(since fluorine is more electronegative oxygen has +2)
and in peroxides like h202 where it is -1
oxidation state of hydrogen is
-1 when combined with metals (less electronegative)
+1 when combined with more electronegative elements (non metals)
Hydrogen in -1 oxidation state is called
hydride ion
NAME
N02-
N03-
S032-
S042-
Nitrite (III)
Nitrate (V)
Sulfite (IV)
Sulfate (VI)
Discontinuity in ionization energy between berrylium and boron
Berrylium - 1s2 2s2
Boron - 1s2 2s2 2p1
Even though boron has greater charge its its outermost electron is in the 2p orbital, which is higher in energy and less stable than the 2s orbital of Be.
easier to remove lone electron rather than paired electron
Discontinuity in ionization energy between nitrogen and oxygen
Nitrogen - 1s2 2s2 2p3
Oxygen - 1s2 2s2 sp4
In nitrogen the 3 electrons do not come into close proximity, the paired electrons in oxygen occupy the same region of space and have increased repulsion so its easier to remove
definition of transition elements (2)
element that has a partially filled d sublevel
or can form a stable cation with an incomplete d sublevel
why do transition elements have a high melting point
d electrons have high energy and are delocalised,
this attraction between the delocalised electrons and metal ions is very strong
why is zinc not a transition element
does not form cations with incomplete d sublevel
its 4s2 3d10, so it loses 2 electrons but still has an inctact 3d10 sublevel
define catalyst
species that reduces the activation energy required for a reaction to occur while not being used up in that reaction
define heterogeneous catalysts
type of catalyst that exist in a separate phase to the reactants.
how are transition elements used as catalysts
transition elements are used as heterogenous catalysts as gas molecules get absorbed on their solid surface and the molecules undergo chemical changes.
the molecules then desorb off the catalyst
examples of transition elements used as heterogeneous catalysts and in what?
platinum, palladium and rhodium are used in catalytic converters
catalytic converters def + eq
absorb carbon monoxide and oxygen molecules in the exhaust and desorb carbon dioxide
2C0 + 02 = 2C02
how do transition elements form variable oxidation states
Transition elements form variable oxidation states because their 4s and 3d electrons have similar energy levels, allowing the removal of different numbers of electrons with low energy differences.
ligand definition
molecules or ions with a lone pair of electrons that can be donated to the cation of a transition element to form a coordination bond
transition elements forming coloured compounds known as ___ when bonded with ligands
complex ions
what happesn when ligands form a coordination bond in terms of orbitals
first, they are degenerate (same energy)
then oribitals in the d sublevel are split into 2 sets with different energies
the energy gap between the orbitals corresponds to a wavelength within the visible light region of the electromagnetic spectrum
how do lower energy oribtals climb to higher energy orbitals in a complex
difference in energy between split orbitals allows lower electrons to be promoted into higher orbitals.
the complex absorbs light with a wavelength corresponding to teh energy gap between the non - degenerate orbitals
once energy is absorbed what colour is shown in complex
the colour observed is the complementary colour to the colour absorbed
complementary colours state
RED GREEN
ORANGE BLUE
VIOLET YELLO W
Race Goals, Outrun Battles, Victory’s Yours.”
speed formula
speed = frequency x wavelength
energy formula
Planck constant (6.63 x 10^-34) x Frequency
the larger the splitting between oribtals
light shud have?
the greater the energy required to promote the electron
for large splitting light should have low wavelength and higher freeq
