Electron Configuration Nucleus is (+) because it is composed of neutrons (0) and protons (+). Atoms = neutral, therefore #p (+) = #e- (-). Electrons determine the chemical properties of an atom. Nucleus changes during nuclear reactions, but remains unchanged during chemical and physical changes. Electrons do not get away because the (-) charge is attracted to the (+) nucleus.

We describe light as a wave with a: A) Frequency (V) - number of cycles or peaks per second. Units: (cycles/sec) = hertz B) Wavelength ( ) - distance from peak to peak. C) Speed - (C) - all light has the same speed = 3.00 X 10 8 m/s 3.00 X cm/s

Neils Bohr (1913) - Theory of Electron Behavior 1) Electrons are like planets - they orbit the nucleus in certain circular paths - INCORRECT! 2) Electrons can only have certain amount of energy - TRUE! Quanta or photons. 3) Electrons in orbit will not lose energy due to radiation: (+) nucleus holds e-(-) in place - TRUE! 4) Electrons pick up enough energy to get exactly to another orbit. Then they emit the asorbed energy in the form of light and return to their original orbit - TRUE!

How does Bohr explain spectral lines? Since e- can only pick up certain amounts of energy (quanta or photons of energy) to get exactly to another energy level they can only emit certain amounts of energy as well. That is why we can only see certain colors at certain wavelengths. Things to know: Electrons only give off energy when they return to a lower energy level. Highest probablity of finding an electron is in the electron cloud where it is most dense.

The position of the electron can be represented by a cloud. Electrons behave as particles and waves. All chemical behavior centers around the behavior of the electrons (specifically the valence = outer shell electrons).

Electron Behavior (1) energy level (n) - a group of electrons with the same amount of energy (not a place). n = 1,2,3,4,5,6,7 Electrons can only have seven different amounts of energy = energy levels. Energy level = shell = k,l,m,n,o,p,q Energy level = Principle quantum number. 1st energy level is the lowest in en - closest to the nucleus. 7th energy level is the highest in en - furthest from the nucleus.

2) subshell or sublevels = ways electrons carve out space or the path of the electron. Basically 4 ways that electrons carve out space = s,p,d,f e- in an s carve out space in a spherical shape. p e- carve out space like a figure 8 or 2 footballs pointing toward the nucleus. The shape of the d and f subshell are 3-D and are very complex!

Arrangement of electrons = Electron configuration Very important because it determines the chemical properties of the element. Basic law of nature: things seek positions of lowest energy, therefore we would expect the 1st en level to fill, then the 2nd, 3rd, 4th, and so on. Nearly true, but some complications. Energy levels do not completely fill before the next one starts to fill. Often small subshells of higher en levels are filled before large subshells of lower en levels.

Wave mechanical view of the atom Schrodinge Heisenberg, de Broglie, and Schrodinger helped to develop a theory of atomic structure. Electrons do not have paths like the planets, therefore it is impossible to determine the exact location of an electron at any given time. Heisenberg’s Uncertainy Principle: It is impossible to know both the position and the momentum of an e- at the same time. Schrodinger’s equation - dev. an equation to tell where the electron is at a given point in time.

Quantum numbers These are the variables that go into Schrodinger’s eq. Pauli exclusion principle: no 2 e- can have the same 4 quantum numbers. 1) Principle quantum # (n) - indicates the most probable distance of the e- from the nucleus. Relates to the overall en of the e-. n = 1,2,3,4,5,6,7

2) Angular momentum quantum number (l) - relates to the shape or the volume that the wave is in (subshell). l = > (n-1) 3) magnetic quantum number (m l ) - related to the direction in space or the orientation (# of orbitals) m l = -l -----> > +l