Structure of Atom Flashcards
Electromagnetic Radiation
Charged particles under acceleration producing alternating electrical and magnetic fields
Isotopes vs Isobars vs Isotones
Isotopes: Atoms of the same element which have the same atomic numbers but different mass numbers
Isobars: Atoms of different elements having the same mass numbers but different atomic numbers
Isotones: Atoms having same number of neutrons but different mass numbers
Relation between c, mu, lambda
c = (mu)(lambda)
Wavenumber
Number of wavelengths per unit length = 1 / lambda
Give the electromagnetic spectrum (in increasing wavelength)
gamma rays < X rays < UV < visible < IR < Microwave < FM < AM < long radio
Give the electromagnetic spectrum (in increasing frequency)
Long radio > AM > FM > Microwave > IR > visible > UV > X rays > gamma rays
Black Body Radiation Explanation
- When solids are heated they emit radiation over a wide range of wavelengths
- When an iron rod is heated, it turns to dull red and then progressively more and more red as temp increases
What is black body radiation?
The ideal black body, which emits and absorbs radiations of all frequencies, is called a black body and the radiation emitted by such a body is black body radiation
Relation between E, h, mu
E = h (mu)
Photoelectric effect + results
Electrons are ejected from certain metals when exposed to a beam of light
* Ejected as soon as light strikes the surface
* No. of electrons proportional to intensity
* Existence of minimum frequency
Relation between intensity and no. of electrons ejected
Directly proportional
Threshold frequency
Frequency below which photoelectric effect is not observed
Relation between frequency and KE
Directly proportional (Greater energy by photon = greater KE - greater frequency of photon)
Photoelectric effect equation
h(mu) = h(mu0) +1/2 mv^2
Longest wavelength
Red colour
Spectrum
Ray of white light is spread out into a series of coloured bands
Emission spectrum
Spectrum of radiation emitted by a substance that has absorbed energy
Absorption spectrum
When light is passed through unexcited atomic hydrogen and transmitted light is lacking in intensity
Wavenumber formula (Rydberg’s)
(mu)_ = 109,677 (1/n1^2 - 1/n2^2) cm^-1
Angular momentum formula
mvr = nh/2pi
All light spectrum correspondance
Lyman - Ultraviolet (Till n=1)
Balmer - Visible (Till n = 2)
Paschen - Infrared (Till n=3)
Formula of radius of bohr orbit
r = a(n^2)/Z
a = 52.9 pm
Convert:
1) picometer
2) nanometer
3) Armstrong
4) Micrometer
1) 10^-12m
2) 10^-9m
3) 10^-10m
4) 10^-6m
Ionized hydrogen atom
When an electron is taken free from the influence of nucleus, the energy is taken as zero. The electron in this situation is associated with the stationary state of Principal Quantum Number = n = infinity
Formula of E {Rydberg’s}
E = -Rh(Z^2/n^2)
Rh = 2.18 * 10^-18J
Magnitude of velocity of electron
Increases with positive charge on nucleus
Decreases with increase in principal quantum number
For which species can Bohr’s theory by applied
- Isoelectronic species having one electron
- H, He+, Li2+, Be3+, etc.
What happens when n1 > nf
Delta E is negative and energy is released
What does the brightness / intensity of spectral depend upon?
Number of photons of same wavelength or frequency absorbed or emitted
Relation between wavelength and momentum (dual behavior)
lambda = h / mv = h / p
Heisenberg Uncertainty Principle
Impossible to determine simultaneously, the exact position and exact momentum of an electron
Heisenberg Uncertainty Principle Formula
delta x * delta mv >= h / 4 pi
Principal quantum number
- Determines size and to large extent the energy of the orbit
- Identifies the shell
- Ranges from 1 to n
Number of allowed orbitals
n^2
With increase in ‘n’ value what increases?
- Energy
- Size of orbital
Azimuthal quantum number
Defines the 3D shape of the orbital
What do ‘l’ values range from
0 to (n-1)
How many subshells are there?
n total
Magnetic orbital quantum number
Gives information about spatial orientation of the orbit with respect to standard set of co-ordinate axis
How many possible values of magnetic quantum number
2l + 1
Electron spin
Can have two orientations relative to chosen axis {Spin of the electron}
nodes
Refers to the area / region where probability density function reduces to zero
Nodes:
1) Total
2) Radial
3) Angular
1) n-1
2) n - l -1
3) l
Draw 2px, 2py, 2pz
-
Draw dxy, dyz, dxz, d(x^2-y^2), dz^2
-
Degenerate
Orbitals having the same energy
Effective nuclear charge
The attractive positive charge of nuclear protons acting on valence electrons
Formula of Zeff
Zeff = Z - S
Z = atomic number
S = number of shielding electrons
Relation between l and Zeff and why?
Inversely proportional
Increase in azimuthal causes s electron to be more tightly bound to the nucleus than p electron which in turn will be more tightly bound than the d electron
Energy of orbit formula (using n and l values)
n+l
Aufbau Principle
In the ground state of the atoms, the orbitals are filled in order of increasing energies
Pauli Exclusion Principle
- No two electrons in an atom can have the same set of four quantum numbers
- Only two electrons may exist in the same orbital and these electrons must have opposite spin
Maximum number of electrons in shell with principal quantum number n
2n^2
Hund’s rule of maximum multiplicity
Pairing of electrons in the orbitals belonging to the same subshell does not take place until each orbital belonging to that subshell has got one electron each
Valence Electrons
Electrons in the completely filled shells are known as core electrons and electrons added to electronic shell with highest principal quantum number
Config of copper and chromium
Chromium: 1s2 2s2 2p6 3s2 3p6 4s1 3d5
Copper: 1s2 2s2 2p6 3s2 3p6 4s1 3d10
Explain copper and chromium’s electronic config
- Fully filled and half-filled orbitals have extra stability
- Hence, they take on that config
Causes of stability of completely filled and half filled sub-shells
- Symmetrical distribution of electrons
- Exchange energy - Maximum and hence max stability
Fe2+ configuration
1s2 2s2 2p6 3s2 3p6 3d6
We have to remove from the valence electron shell first
