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3.5 Atomic Theory for those in a Hurry

3.8 Nomenclature

3.11 Covalent Bonding

# Atomic Theory for those in a Hurry

Let's face it - a LOT of science and hard work went in to get us to modern day atomic theory. You are going to study the tail end of it all. I'm not even going to hound you about the details leading up to it. It was really hard. Lots of math/differential equations, experiments, analyzing line-spectra developing models, and on, and on... The valuable bits for US is the outcome from all of that. Before I go on though, here is a graphic with lots of stuff in it - all part of modern day atomic theory.

#### THANK YOU! smart people!

We thank them for their service and contributions to science. So what do YOU need to know from all of that? Energy Levels! Let's dig in and get those sorted out.

#### Atomic Theory and Schrodinger Equation Outcomes

1. atoms have a nucleus consisting of protons and neutrons
2. the nucleus has about 99.95% of the mass of the atom but only 1/35000th of its radius*
3. the nucleus is surrounded by electrons
4. the number of electrons equals the number of protons for all neutral atoms
5. electrons are in discrete energy levels within the atom
6. the energy scale is negative meaning the lowest level is the one that is the biggest negative number
7. the actual solutions to the Schrodinger equation are wavefunctions - they map out three dimensional regions of space around the nucleus where we find electrons - we then rename them orbitals
8. there are main levels and then sub-levels within those main levels
9. the levels are not evenly spaced in energy - each new level from bottom to top is closer than the previous level
10. we have a great numbering system (quantum numbers) for all the levels that works in parallel with the way the periodic table is laid out.
11. the numbering system can go all the way to infinity for main levels - however, we only need 8 for our current set of elements
12. if an electron is promoted up the ladder of energy, it can escape the atom (nucleus) and be a free electron
13. a free electron by definition has zero energy on this scale and is technically at the infinite level

* the relative masses of electron : proton : neutron are 1 : 1836 : 1839
average radius of an atomic nucleus is 3 fm while the atom itself is more like 105 pm which is a factor of 35000. If you calculate volumes off of those radii, you'll find that the nucleus occupies only 0.0000000000023% of the space of an atom. The other 99.9999999999987% is occupied by the electron cloud surrounding it.