Electronic structure of atoms

• State Bohr’s Assumptions

  1.Electrons move in circular orbits round the nucleus.

  2.Electron can transfer from one energy level to another when it absorbs or emit energy.

  3.When electron absorbs photon or packet of energy, it jums to higher energy level.
• Under assumption one

  Each orbit corresponds to a definite?


  energy level
• Under assumption 1

  Electrons move in circular orbits round the nucleus.

  ✓Each orbit corresponds to a (a)

  ✓Energy levels (b) as its

  distance from the nucleus

  increases.

  ✓Each orbit contains definite

  number of (c).

  ✓As electron remains in that

  orbit, (d).

  ✓Electron energy is (e).

  a.definite energy level

  b.increases (or directly proportional)

  c. electrons

  d. no absorption or emission of electrons occur

  e. fixed
• Under assumption 2

  Electron can transfer from one energy level to another when it absorbs or emits energy

  ✓Each energy level is

  designated a positive

  integer (n) (a)

  ✓n=1, (b)most

  stable.

  a-principal quantum number

  b-ground state
• Under Assumption 3

  When electron absorbs photon or packets of energy, it “jumps” to higher energy level.

  ✓Stability of e (a)as it

  gets excited.

  ✓Energy is (b) when e

  falls back to lower energy

  level.

  ✓Only certain colors of light

  are produced because only

  certain discrete amounts of

  energy are released.

  a.decreases

  b.released
• Numbers that describe

  the energies of electrons in atoms; derived

  from quantum mechanical treatment.

  Consist of primary, secondary, magnetic, and

  spin numbers.


  Quantum numbers
• It can have integral values 1, 2, 3, and so forth.

  It also relates to the average distance of the electron from the nucleus in a

  particular orbital. The larger n is, the

  greater the average distance of an

  electron in the orbital from the nucleus

  and therefore the larger the orbital

  Principal Quantum Number
• Designates the shape of the region in space that an electron occupies

  It designates a sublevel, or specific shape of atomic orbital that an electron may occupy.

  This number, may take integral values from 0 up to and including (n -1)


  Angular Momentum Quantum number
• • designates the specific orbital within a subshell . Orbitals within a given subshell

  differ in their orientations in space, but not

  in their energies. Within each subshell, it

  may take any integral values from through

  zero up to and including :

  ml = (- l), . . . , 0, . . . , ( + l)

  The maximum value of fe on the value of l


  Magnetic Quantum Number
• In describing ground state electron

  configuration, the guiding idea is that the

  total energy of the atom is as low as

  possible.
• dictates that as protons are added one by one to the nucleus to build up the

  elements, electrons are similarly added to the atomic orbitals.

  • electrons fill orbitals starting at the lowest available energy state

  before filling higher states

  Aufbau Principle
• No two electrons in an atom may have

  identical sets of four quantum numbers.

  Atomic orbital can contain at most

  two electrons with opposite

  spins.


  Pauli Exclusion Principle
• the most stable arrangement of electrons in subshell is the one with the greatest number of parallel spins.

  In orbitals of the same subshell,

  electrons are filled singly first

  before pairing starts

  Hund’s Rule
• HYDROGEN ABSORBS WHAT COLOR

  blue,purple,res
• electron capacity of subshell formula

  4l+2
• electron capacity of shell

  2n^2
• the values n,ml, and ms describe a

  particulr atomic orbital
• each atomic orbital can accomodate no more than 2 electrons


  one with ms -1/2 and one with ms+1/2
• S orbitals has 2 electrons

  p orbitals has 6 electrons

  d orbitals has 10 electrons

  f orbitals has

  14 electrons
• Electrons occupy energy levels called electron shells or principal quantum levels.
• The first shell is the closest to the nucleus; it contains only two electrons.
• The second shell holds eight electrons (two s-orbitals and three p-orbitals).
• Noble gases and their number of electrons

  helium-2

  neon-10

  argon-18

  krypton-36

  xenon-54

  radon-86
• It does not follow aufbau principle, because half-filled orbitals are more stable than other conifgurations

  Cr
• Does not follow aufbau principle as completely filled orbitals are more stable than half-filled.

  Cu
• It shows when an electron is excite and jumps into a higher ortbital. From ground state to a higher energy orbital.

  Excited State Electron Configuration
• Al-13 ground state

  1s2 2s2 2p6 3s2 3px1
• Al-13 excited state

  1s2 2s2 2p6 3s1 3px1 3py1
• Carbon-6 ground state

  1s2 2s2 2px1 2py1
• Carbon-6 excited state electro configuratuon

  1s2 2s1 2px1 2py1 2pz1
• Have exceptional electron configuration

  Cr- half-filled is more stable

  Cu-completely filled is more stable

  Ag-completely filled is more stable

  Mo-

  Au-

  Pd
• Principal Quantum number (n) describes the average distance.

  Angular Momentum quantum number (l) describes the shape of the region in space.

  Magnetic Quantum number (l) describes the spatial orientation of the orbital.

  Magnetic Spin Quantum Number (Ms) describes the

  spin and the shape of the magnetic field the electron has produce
• Among the various quantum number which can have the largest value?


  Principal Quantum Number