Atomic Structure, Periodicity and Bonding

1
Atomic Structure, Periodicity and Bonding
2
Important Scientists Contributions

• Dalton
• Thomson
• Rutherford
• Chadwick
• Milikan
• Lavoisier

3
1989

• Which of the following conclusions can be drawn
  from J.J. Thomsons cathode ray experiments?
• a.) Atoms contain electrons
• b.) Practically all the mass of the element is
  contained in the nucleus
• c.) Atoms contain protons, neutrons and
  electrons
• d.) Atoms have a positively charges nucleus
  surrounded by an electron cloud
• e.) No two electrons in one atom can have the
  same four quantum numbers

4
Isotopic Notation
Mass Number
Charge

• 118
• 42
• Be able to determine protons, neutrons, electrons
  and to identify isotopes

Mo
Atomic Number
5
Nuclear Decay

• Alpha particle helium nucleus, most mass,
  slowest, least penetrating, released from heavy
  nuclides
• Beta Particle mass of electron, negative,
  released when n/p ratio is too high, converts n?
  p
• Positron mass of electron, positive, released
  when n/p ratio is too low, converts p? n
• Gamma Particle no mass, high frequency
  radiation, most penetrating
• List the symbols for each

6
1994 21

• Correct statements about alpha particles include
  which of the following?
• I. They have a mass number of 4 and
• a charge of 2
• II. They are ore penetrating than beta
• particles
• III. They are helium nuclei

7
1989

• 251 131
• 98 54
• What is the missing product in the nuclear
  reaction?
• Mo b. Ru
• c. Mo d. Pd

Cf? 2n
Xe .
118 42
120 44
122 46
120 42
8
1984

• When Po-214 decays, the emission consists of
  consecutively, an alpha particle, then two beta
  particles, and finally another alpha particle.
  The resulting stable particle is
• a. Bi b. Bi
• c. Pb d. Pb
• e. Tl

210 83
206 83
206 82
208 82
21081
9
The Electron and the atom

• Scientists
• Plank
• Einstein
• DeBroglie
• Bohr
• Heisenberg
• Schrodinger
• Aufbau
• Pauli
• Hund

10
1984

• a. Heisenberg Uncertainly Principle
• b. Pauli Exclusion Principle
• c. Hunds Rule
• d. Shielding Effect
• e. Wave Nature of Matter
• Can be used to predict that a gaseous carbona tom
  inits ground state is paramagnetic
• Explains the experimental phenomenon of electron
  diffraction
• Indicates that an atomic orbital can contain no
  more than 2 electrons
• Predicts that it is impossible to determine
  simultaneously the exact position and velocity of
  an electron.

11
Quantum Numbers
12

• What are the quantum numbers for
• the outermost valence electron?Are they
  paramagnetic or diamagnetic?
• S ?
• Cd ?
• La ?
• Hf ?

13
Sulfur

• Since the last electron put in is 16 and it is
  in the 3p sublevel, n 3 and l 2.
• Its in the -1 slot, the ml -1.
• And, since its the second arrow placed down
  arrow its ms -1/2.
• So the set of quantum numbers for the 16th
  electron in sulfur is 3,2,-1, -1/2.

14
You accepted that the sublevels had differences
in energies long ago.

• You even know the increasing order of energies
  s lt p lt d lt f lt g
• Some fundamental scientific principles that you
  need to be able to mention when explaining the
  quantum numbers
• electrons repel each other
• electrons are attracted by the positive nucleus
• forces dissipate with increasing distance.

15

• See the small hump near the origin?
• Thats the
• distance from
• the nucleus that
• a 2s electron
• occupies a
• small but
• significant
• amount of the time.

16

• We say the electron penetrates to
• the nucleus more than for the 2p
• orbital.
• This causes a 2s electron to be
• ATTRACTED to the nucleus more
• than a 2p electron making the 2s
• orbital LOWER in E than the 2p
• orbital.

17
1980

• Write the ground state electron configuration for
  an arsenic atom, showing the number of electron
  sin each subshell
• Give one permissible set of four quantum numbers
  for each of the outermost electrons in a single
  As atom when it is in its ground state
• Is it paramagnetic or diamagnetic, explain.
• Explain how the electron configuration of the
  arsenic atom in the ground state is consistent
  with the existence of the following compounds
• Na3As AsCl3 and AsF5

18
Periodic Properties

• How do each of these change and why?
• ATOMIC Radius
• Ionic Radius
• Ionization Energy
• Electron Affinity
• Things to remember
• Effective nuclear charge increasing number of
  protons attract valence electrons in the same
  energy level more effectively
• Shielding as additional energy levels of
  electrons are added, the ability of the nucleus
  to attract the valence electrons is diminished