Arrangement of Electrons in Atoms
Review
Rutherford - Gold Foil Experiment
Discovered the nucleus - a hard dense small center of the atom containing the _______________ and _______________
Most of the atom is empty space in which the _______________ move randomly throughout
Rutherford did not explain how the electrons filled the empty space surrounding the nucleus.
The Development of a New Atomic Model
I. Properties of Light
A. _______________Description of Light
i. Electromagnetic _______________ - * is a form of energy that exhibits wavelike behavior as it travels through space. Energy lost or gained as the electron moves from one energy level to another. (Only some are visible.) ii. Electromagnetic _______________ - consists of radiation over a broad range of wavelengths; includes radio waves, radar waves, microwaves, infrared waves, visible light waves, ultraviolet waves, x-rays, gamma rays, and cosmic rays. (Listed from longest λ to the shortest λ)
B. Light Behavior Review
i. _______________ = Electromagnetic Radiation (Energy that travels as a wave)
Electromagnetic Radiation: *energy lost or gained as the electron moves from one energy level to another (only some are visible) ii. All forms of electromagnetic radiation move at a constant speed of 3.00 x 108 m/s iii. _______________ (λ) is the distance between corresponding points on adjacent waves. iv. _______________ (ν) is defined as the number of waves that pass a given point in a specific time, Usually one second. Units of frequency: cycles/second or hertz (SI) v. Frequency and wavelength are mathematically related to each other: c = λν vi. In the equation, c is the speed of light (in m/s), λ is the wavelength of the electromagnetic wave c is the same for all electromagnetic radiation, c = 3.0 x 108 m/sec, which means wavelength and frequency are inversely proportional, when one goes up the other goes down. Ex: as the wavelength of light decreases, its frequency increases
II. The Photoelectric Effect
A. photoelectric _______________ *refers to the emission of electrons from a metal when light shines on the metal. *electrons are ejected by metals when light shines on them - light waves act like particles (Einstein). The energy of the light has to be at a certain minimum. Light can be absorbed or emitted by matter. Example: Calculators that require light to work. 1. For a given metal no e- were emitted if the lights frequency was below a certain minimum. 2. The wave theory of light predicted that any frequency of light should knock loose an electron. B. The Particle Description of Light i. Quantum* the minimum quantity of energy that can be lost or gained by an atom. ii. German physicist Max Planck proposed the following relationship between a quantum of energy and the frequency of radiation E = hν
a. E is the energy, in joules, of a quantum of radiation, ν is the frequency, in s−1, of the radiation emitted, and h is a fundamental physical constant now known as Planck’s constant; h = 6.626 × 10−34 J• s. iii. The photoelectric effect could only be explained if light acted like a particle & a wave.
The particles of light carried energy which knocked the electrons out of the atom. iv. A photon is a particle of electromagnetic radiation having zero mass and carrying a quantum of energy. The energy of a particular photon depends on the frequency of the radiation Ephoton = hν
III. The Hydrogen-Atom Line-Emission Spectrum A. _______________ State * the lowest energy state of an atom (n = 1 is the lowest energy level) i. Absorption* the process in which energy must be added to an atom in order to move an electron from a lower energy level to a higher energy level B. _______________ state* a state in which an atom has a higher potential energy than it has in its ground state i. Emission * process when an electron falls to a lower energy level and a photon is
