Electron Structure

Bohr Model Used to explain the structure of the Hydrogen Atom –Hydrogen has only one electron This electron can only circle the nucleus in fixed paths called orbits. Energy levels As the energy levels distance from the nucleus increases so to does the energy of the electron –These energy levels are fixed in distance and energy, this is referred to as a quantum.

The state of lowest energy that an atom can exist in is called its ground state. –Any energy level higher than this is called an excited state. It takes energy to move an electron to a higher energy level. –If this happens the atoms is now in an excited state. If an electron moves from a higher energy level to a lower energy level, energy is released as a photon. –Energy can only be gained or lost by an atom in specific amount. This amount is called a quantum, and maybe different for different atoms. –Photon a specific quantum of light energy. –Losing a photon will work to return the atom to its ground state.

Bohr Model

Applet plets/Bohr/applet_files/Bohr.html

Electromagnetic Spectrum Light can be described as a wave –The wave length is the distance between two reoccurring points on the wave. This is symbolized by the Greek letter lambda λ –The velocity of light is always a constant 3 x 10 8 m/s, this is symbolized with the letter c –The frequency of light is symbolized with a v and is defined as the number of waves that pass a given point in a specific amount of time. Given in units of Hertz or Hz which are cycles per second.

The relationship between these parts of a wave is that c=vλ –As wave length goes down the frequency of the photon goes up. Radiation is emitted and absorbed in whole numbers of photons, described by the relationship: –E=hv E=energy h=Planck’s constant x J*s (joules per second)

These two equations relate the frequency of a photon of light to its energy. –Find the wavelength of light if its frequency is 7.5 x 10 2 Hz –Determine the energy in joules, of a photon whose frequency is 3.55 x Hz

Quantum Numbers and Atomic Orbital's Quantum numbers –These are numbers that specify the properties of the atomic orbital's and of their electrons. Principal quantum numbers (n) –Indicates the main energy levels surrounding a nucleus, referred to as shells –These are whole numbers which increase as their distance from the nucleus increases. Their energy increases as their number increases.

Orbital quantum number –This number indicates the shape of an orbital »Within each main energy level beyond the first, orbital's with different shapes occupy different regions »In order of energy they are as follows »s »This orbital has only one sublevel and can have 2 electrons in it

»p orbital »This orbital has 3 sublevels and can have 6 electron in it

»d orbital »This orbital has 5 sublevels init and can have 10 electrons in it

The f orbital has 7 suborbital's and can have 14 electrons in it. Spin quantum number –This number can have only 2 values +1/2 or -1/2

Electron Configurations This is a way to describe how the electrons are arranged around a nucleus. –It uses the quantum numbers to do this. –Follows the Aufbau principle, electrons will occupy the lowest energy level that they can. –Hund’s rule also applies Orbital’s of equal energy are each occupied by one electron before any is occupied by a second electron.

–Pauli exclusion principle also applies. No two electrons in the same atom can have the same four quantum numbers. Orbital notation –Uses lines to represent orbitals When filled electrons are represented by up arrows and down arrows. The lines are labeled with the principal quantum number and subshell letter.

Aufbau chart –This shows how the energy levels are filled and in what order.