enriched chem Flashcards
two types of solids
amorphous and crystalline
define amorphous solid
local ordering and lack any long range 3D order and structure, solutions that have been frozen in place before reaching a high ordered structure (ex glass)
define crystalline solid
long range repeating 3D structures. Most elements and solid compounds form crystalline solids
classifications of crystalline solids
atomic solids = only atoms in crystal structure (ex diamond)
ionic solids = made from ions (ex salt)
molecular solids = molecules dispersed through crystal structure (ex ice)
definition of crystal lattice
molecules or ions are in a regular 3D pattern called a crystal lattice made up of repeating sub units (unit cells)
name all crystal systems (unit cells)
cubic tetragonal orthorhombic monoclinic hexagonal rhombohedral triclinic
name the bravais lattices for cubic crystal system
simple cubic = atoms at corners of cube (total = 1 atom)
body centred cubic = corners and one in centre (total = 2 atoms)
face centred cubic = corners and six faces of cube (total = 4 atoms)
how are layers placed in a closest packed structure (1st + 2nd)
on top of one another in an offset pattern, 2nd layer placed in indentations of first
state the packing efficiency for the cubic bravais lattices
simple = least efficiently packed 52% body = 68% face = most efficiently packed 74% (closest packed structure for a collection of spherical objects)
characteristics of crystal systems
cubic Y = 90, B = 90, A = 90, a, b=a, c=a
tetragonal Y = 90, B = 90, A = 90, a, b=a, c
orthorhombic Y = 90, B = 90, A = 90, a, b, c
monoclinic Y, B = 90, A = 90, a, b, c
hexagonal Y = 120, B = 90, A = 90, a, b=a, c
rhombohedral A, A, A, a, b=a, c=a
triclinic Y, B, A, a, b, c
describe placement of 3rd layers
3rd layer determines type of crystal system
placed directly above first layer = ABA system which forms hexagonal unit cells (ex of hexagonal closest packed structure)
placed not above first or second layer = ABC system which forms face centred cubic cells (ex of cubic closest packed structure)
describe allotropes of carbon
graphite, diamond and buckminsterfullerenes
define allotropy
the existence of different forms of the same element
define allotrope
distinct forms of an element generally in the same phase
characteristics of buckminsterfullerenes
discovered in 1985, they are molecules comprised of 60 carbon atoms and are shaped like soccer balls
characteristics of diamond
extremely hard, each carbon atoms is covalently bonded to four other carbon atoms in a tetrahedral structure which imparts great rigidity. no delocalized electrons so it doesn’t conduct electricity, less thermodynamically stable than graphite but forms under higher conditions of pressure
describe allotropes of sulfur
sulfur can be found in minerals, pyrite FeS, PbS, cinnabar, HgS, has more allotropes than any other element
in solid state = rhombic sulfur and monoclinic sulfur, both are made from the same s8 crown shaped ring
in gas state = sulfur in the s s2 s4 s8 forms are observed under different conditions of temperature and pressure
in liquid state = long polymeric chains of sulfur exist
characteristics of graphite
soft and slippery material, ideal for writing, carbon atoms bonded together in hexagonal sheets, layers interact weakly and slide across each other allowing graphite to be deposited, graphite conducts electricity, each carbon is covalently bonded to three other carbon atoms per layer leaving one delocalized electron per carbon
characteristics of rhombic sulfur
most stable form of sulfur, made up of cyclic s8 molecules, heating rhombic sulfur to 120 and slow cooling it gives monoclinic sulfur
characteristics of monoclinic sulfur
below 96 monoclinic sulfur converts back to rhombic
describe allotropes of tin
tin is found in ore cassiterite SnO2, elemental tin is produced by reducing SnO2 w/ carbon source in furnace formula
gray tin and white tin
transition at 13 = very slow, occurs rapidly at very cold temps, white to gray tin is disintegration (tin disease)
characteristics of gray tin
at temps below 13 gray tin is most stable, brittle non metallic powder
characteristics of white tin
at temps above 13 white tin is most stable, metallic solid
describe allotropes of phosphorus
phosphorus is mainly found in phosphate minerals called fluorapatites, elemental phosphorus produced industrially by reacting fluorapatite derivative, phosphate rock with quartz sand, SiO2 and carbon in a furnace, cooled equation
white phosphorus and red phosphorus
characteristics of white phosphorus
white waxy solid, highly reactive and toxic, spontaneously ignites in air so stored in water, insoluble in water, soluble in some organic solvents like CS2, reactivity due to its structure, four phosphorus atoms bonded to each other in tetrahedral pattern, bond angles of 60 in p4 molecule deviate from ideal bond angles of 90, angle strain increases potential energy (reactivity), used for industrial production of phosphoric acid H3PO4 equation
characteristics of red phosphorus
produced by heating white phosphorus to 400, heating white phosphorus in a place devoid of oxygen causes one p-p bonds per molecule of p4 to break, p4 fragments rejoin and form polymeric structure, air stable, less reactive, insoluble in CS2, used to make striking surfaces for matches
rutherfords model limitations
alternating charges should radiate energy, so orbiting electrons should radiate energy and collapse into nucleus within 10^-10 s
bohr model limitations
can be extended to calculate ionization energy and bohr radius of hydrogen and can extend to ionic species with one electron, but bohr model doesn’t work for polyelectronic systems
quantum mechanical systems of schrodingers wave equation and heisenbergs matrix molecules superseded bohrs model
rydberg formula
sub in R(sub)H / hc as 1.097 * 10^7 n/m (link to balmer formula n(sub)f =2, was instance of rydberg formula
1/(lambda)y = R(sub)H / hc (1/n(sub)f^2- 1/n(sub)i ^2)
describe balmer series
distinct bands = balmer series resulted from electronic transitions in excited state hydrogen atoms between higher orbits and the n = 2 orbit
describe paschen series
infrared region, higher energy levels to n=3 orbit
describe lyman series
ultraviolet region, higher orbits to n = 1 orbit
formula for energy of emitted photon
E = hv = -(delta)E = - (Ef-Ei)
niels bohr model
electrons orbit nucleus in specific orbits, orbits were quantized, if electron stayed in a given orbit the electron wouldn’t radiate energy, electrons can transition between energy levels but couldn’t be in between adjacent orbits
atoms absorb energy = lone electron transitions to higher energy orbit
atoms emits energy = lone electron transitions to lower energy orbit (emits photons in process)
early models of the atom (democritus, boyle, lavoisier)
democritus = all matter is made up of small invisible particles boyle = gases lavoisier = conservation of mass in reactions (+ boyle = laid empirical foundation of chemistry as a quantitative science)
dalton
modern atom theory, elements were made up of atoms and the atoms of each element were unique in some way, chemical compounds were created by combining different elements in constant proportions, chemical reactions were the reorganization of atoms and recombined into new chemical compounds, atoms were neither created nor destroyed
thomson
discovers electrons, negatively charge subatomic particles, speculated that there were diffuse positive charges inside atom **plum pudding model
rutherford
disproved plum pudding model, gold sheets and bombarded with radioactive positively charged alpha particles, most went through foil but some small amounts of particles were deflected and bounced back from gold foil, concluded charge wasn’t diffuse but in the area called a nucleus
electromagnetic spectrum spans from
gamma to radio waves
describe wave particle duality
electromagnetic radiation exhibits wave properties and particle properties
describe wave part of wave particle duality
wavelength = lambda, distance between crests or troughs on a wave
frequency = v, number of wavelengths that pass through a point per unit of time, one wavelength (cycle) per second = one hertz (hz)
speed = 2.99 * 10^8 m/s in vacuum
frequency and wavelength are inversely proportional
describe particle part of wave particle duality
stream of particles called photons
energy of photons = frequency times plancks constant, energy is inversely proportional to wavelength
speed of light formula
c = (lambda)y * v
energy formula 1
E = hv
energy formula 2
E = hc/(lamda)y
describe atomic line spectra
atomic solids are heated in flame they produce characteristic colours
hydrogen gas to electrical discharge = produces certain discrete colours, when sample is heated it gains energy and goes into an excited state, for H the H-H bonds are broken which causes individual H atoms to go into an excited state and when they go back to lowest energy state emit excess energy in the form of photons
light emitted by atoms differs from ordinary white light, light emitted from hydrogen atom = discrete bands of light of definite wavelength = atomic line spectra
410 nm, 434 nm, 486 nm, 656 nm
balmer formula
1/(lambda)y = 1.097 / m (1/2^2 - 1/n^2)
volume of atoms in bravais cubic systems
corners v= 1/8 of an atom
centre v=1 atom
faces v=1/2 of an atom
equation to calculate orbits energy
E = R(sub)H / n^2
describe electromagnetic spectrum
gamma rays (10^-12) x rays (10^-10) ultraviolet (10^-8) visible (4 x 10^-7 - 7 x 10^-7) infrared (10^-4) microwaves (10^-2) radio waves (10^2) * fm = 1, shortwave = 10^2 and am = 10^4
visible light = blue - red
blue = 4 x 10^-7, green = 5 x 10^-7, orange = 6 x 10^-7, red = 7 x 10^-7
