Download Atomic Structure—Kitti, Noah, Derek

Atomic Structure—Kitti, Noah, Derek.
Atoms, subatomic particles, molecules, and ions – you know this.
Isotopes – Some elements have varying numbers of neutrons. These are isotopes. Some
isotopes are more stable than others, and the stable ratio of protons to neutrons depends
on the size of the nucleus. In smaller nuclei the ratio is simply 1:1, for the large ones it’s
about 1:1.5.
Carbon-14 is a radioactive isotope of carbon, which typically has 12 protons and
12 neutrons.
Atomic mass – a weighted average of all naturally occurring isotopes. It’s on the periodic
table.
Energy levels – Energy levels are home to electrons. The first one can only hold two
electrons. The second will take eight. And so on.
Excited states – if you add energy to an atom, some of its electrons will move to higher
energy levels (because they have more energy, how clever and self-aware atomic
chemistry is!).
Bohr Model – this is the model responsible for the planetary-style drawings of atoms.
Basically, a hydrogen atom consists of a proton about which an electron orbits; the
opposing charges create an electrostatic force, and the strength of this attraction is related
to the “centrifugal force” due to the circular motion of the electron. If you zoned out
there, here’s the equation that means the same thing: En=-RH/n2 En being the energy of
the electron, RH a constant (2.18x10-18J), and n the principal energy level of the electron
in question. You can calculate the energy required to excite an electron from one energy
level to another. It only works for hydrogen. That’s it! If you can subtract from here,
you’re set for anything anyone could ask you.
Have a sample problem!
Find the energy of an electron in the 3rd principal energy level of a
hydrogen atom: En=-RH/n2 En= -(2.18x10-18)/(32)
CRUNCH! Calculator!
En= -2.2x10-19J
Atomic Spectra – when an electron moves from excited to ground state, it releases
energy, usually in the form of light. The spectra created are unique both to the elements
and energy levels in question.
Quantum numbers – the first quantum number is the number of principal energy levels.
The second is one less than the first. The third is an integer and the fourth is either a
positive or negative ½.