What does an atom really look like

1
What does an atom really look like?

• After Rutherford discovered the nucleus of an
  atom, 2 questions came up
• 1. Why doesnt the nucleus tear itself apart?
• 2. Whats up with those electrons?
• (why dont they fall into the nucleus?)

Chadwick, an associate of Rutherfords, will
answer this question in 1932
Niels Bohr, another associate, will attempt to
explain behavior of electrons
2

• Niels Bohr, Danish physicist
• Proposes that
• Electrons orbit the nucleus in concentric,
  circular paths (orbits)
• Electrons in a particular path have a fixed
  energy electrons do not lose energy cannot
  fall into the nucleus. This Energy Level of an
  electron is the region around the nucleus where
  the electron is likely to be moving.

3

• Important Concepts
• Electrons are quantized found in specific
  energy levels.(n)
• These fixed energy levels of electrons are like
  the rungs of a ladder
• the lowest rung has the lowest energy. Higher
  rungs require higher energy
• electrons can exist in an energy level, or can
  jump from one energy level to another, but
  cannot exist between levels.
• It takes a quantum of energy to move an electron
  from its present energy level to the next higher
  one.
• Within the energy levels, there are sublevels.
  This is because electrons like to arrange
  themselves into regions where they are likely to
  be found. These sublevels are called atomic
  orbitals

4
Erwin Schrödinger, Austrian Physicist

• Wrote a mathematical equation to describe the
  location energy of an electron within energy
  levels.

The answer to his math problems?
3-dimensional shapes!!
Werner Heisenberg, German Physicist
Developed the Heisenberg Uncertainty Principle
You can know the path of an electron as it moves
through space or you can know where it is at a
given moment, but you cannot know both.
This is because electrons act as both waves and
particles.
5
The Quantum Mechanical Model
It also says that because you can never know the
speed of an electron its position at the same
time, you could only guess where an electron was
likely to be 90 of the time

• This model states that electrons still follow
  specific pathways, these orbitals, have specific
  3D shapes

6
In Summary

• The Quantum Mechanical Model is really about
  electrons
• Location and Arrangement

Just Remember Protons give an atom its
identity Electrons give an atom its
personality!!!
7
Electron Configurations

• Since we need to know about electrons, we look at
  the orbitals, and electron arrangement

8
Three Rules for e- configurations

• Aufbau Principle Electrons fill the lowest
  energy level (subshell) first
• Pauli Exclusion Principle Only 2 electrons can
  fill any one orbital. Each one will spin in
  opposite directions.
• Hunds Rule In orbitals of equal energy,
  electrons will spread out among the orbitals
  instead of sharing

9
To build the electron Configuration for Carbon..
1s22s22p2
Increasing Energy
10
What about Flourine?
1s22s22p5
Increasing Energy
11
What about Scandium?
Increasing Energy
1s22s22p63s23p64s23d1
12
Order to fill orbitals