Unit 2 / Matter

Electron Structure of the Atom

General Organization:

I. principal energy level II. energy sublevel III. orbital (shell) (subshell) (electron "parking space")

  • Principal energy level (shell) = period number(n = 1, 2, 3, .... )
  • The shell defines the main energy level of an electron, but not its path
  • all electrons in one shell do not have the same energy. Most shells are made up of several energy levels grouped closely together called energy sublevels (subshells).
  • the subshells are designated with the letters s, p, d, f (instead of 1, 2, 3, 4) and have increasing levels of energy: energy of the subshells ---> s < p < d < f
  • the orbitals represent all the possible locations of an electron in a given energy level based on probability.
  • location of subshell blocks: mark on blank periodic table
  • a maximum of 2 electrons can occupy 1 orbital or “parking space” and the subshells have the following number of available parking spaces:

s subshell - contains 1 orbital

p subshell - contains 3 orbitals

d subshell - contains 5 orbitals

f subshell - contains 7 orbitals

  • Now we can figure out the maximum number of electrons that can occupy each subshell and shell:

Max. # of Electrons Max. # of Electrons

Shell Subshell # of Orbitals In Subshell In Shell

Electron Configurations:

  • this is the shorthand method chemists use to keep track of electrons.

Orbital Diagrams:

  • 1 orbital can only hold 2 electrons. The first e- spins in one direction and the second e- must spin in the reverse direction. e- parking space _____

Hund's Rule

  • we half-fill all orbitals within an energy sublevel before we pair them up. This is a result of the fact that 2 e- in the same orbital tend to repel one another because they are both negatively-charged. If there is an empty orbital of equal energy, the e- will go there first rather than go into an occupied orbital.

Noble gases

  • have filled outermost energy level --> “closed shell”
  • very stable electron arrangement
  • shortcut --> use [noble gas core]

Valence electrons

  • electrons in the outermost energy level/shell
  • except for He, all noble gases have an octet of valence e-
Electronic configurations of ions
  • many ions will lose/gain enough electrons to have the same configuration as a noble gas. When two things have the same electron configuration they are said to be isoelectronic. However, their nuclei will not be the same.

Conclusions:

Things to Think About:

So what is really going on during a chemical change?

What does sodium do in a chemical reaction?

What does chlorine do in a chemical reaction?

How many electrons do they now have?

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Chemistry I Cary Academy W.G. Rushin