Ch 4 Section 1 Flashcards
Visible light is a kind of
Electromagnetic radiation
Together all the forms of electromagnetic radiation form the
Electromagnetic spectrum
Wavelength is the distance between
Corresponding points on adjacent waves
Significant feature of wave motion is its
Rewriting nature which can be characterized by wavelength and frequency
Unit for wavelength
Distance unit (m, cm, nanometer)
Frequency (v) is defined as the number of
Waves that pass a given point in a specific time usually one second
Frequency unit
Waves per second (hertz)
Frequency and wavelength are
Mathematically related to each other
C = wavelength times frequency
In wavelength frequency equation c is the
Speed of light
In wavelength frequency equation wavelength symbol is the
Wavelength of the electromagnetic wave in m
In wavelength frequency equation v is the
Frequency of the electromagnetic wave in s^-1
In wavelength frequency equation the product is a
Constant
Wavelength is
Inversely proportional to v
As wavelength decreases
Frequency increases
The photoelectric effect refers to the
Emission of electrons from a metal when light shines on the metal
Wave theory of light predicted that light of any frequency could supply enough
Energy to eject an electron
A quantum of energy is the minimum quantity of
Energy that can be lost or gained by an atom
Max Planck proposed the following relationship between a quantum of energy and frequency of radiation:
E = hv
In equation E = hv, e is the
Energy in joules of a quantum of radiation
In equation E = hv, v is the
Frequency in s^-1 of the radiation emitted
In equation E = hv, and h is a fundamental
Physical constant known as plancks constant
Plancks constant
6.626 x 10^-34 J • s
Einstein introduced idea that electromagnetic radiation has a
Dual wave particle nature
Electromagnetic radiation is a form of energy that exhibits
Wavelike behavior as it travels through space
A photon is a particle of electromagnetic radiation having
Zero mass and carrying a quantum of energy
The energy of a particular photon spends on the
Frequency of the radiation
Ephoton =
Hv
Electromagnetic radiation is absorbed by matter only in
While numbers of photons
Different metals require different
Minimum frequencies to exhibit the photoelectric effect
When current is passed through gas at low pressure the
Potential energy of the gas atoms increases
Ground state of an atom
Lowest energy state of an atom
Excited state of an atom is a state in which an atom has a
Higher potential energy than it has in its ground state
When an excited atom returns to its ground state or lower energy excited state it gives off
Energy it gained in form of electromagnetic radiation
When investigators passed electric current through a vacuum tube containing hydrogen gas at low pressure the observed
The emission of a characteristic pinkish glow
When a narrow beam of the emitted light was shined through a prism it was
Separated into four specific colors of the visible spectrum
The four bands of emitted light were part of what is known as
Hydrogens line emission spectrum
Scientists had expected to observe the emission of a
Continuous range of frequencies of electromagnetic radiation: continuous spectrum
New atomic theory called the
Quantum theory
Whenever an excited hydrogen atom falls to its ground state or to lower energy excited state it emits a
Photon of radiation
The fact that hydrogen atoms emit only specific frequencies of light indicated that
Energy differences between atoms’ energy stars were fixed
Niels Bohr proposed a hydrogen atom model that linked the atoms
Electron to photon emission
According to the model the electron can
Circle the nucleus only in allowed paths (orbits)
When the electron is in one of these orbits atom has a
Definite fixed energy
The electron is in its lowest energy state when it is in the
Orbit closest to the nucleus
This orbit is separated from the nucleus by a
Large empty space where the electron cannot exists
The energy of the electron is higher when the electron is in orbits that are
Successively farther from the nucleus
An electron can be in one orbit or another but not
In between
While in a given orbit the electron is neither
Gaining nor losing energy
When an electron falls to a lower energy s photon is emitted and the process is called
Emission
Energy must be added to an atom in order to
Move an electron from a lower energy level to a higher energy level (absorption)
Energy of each absorbed or emitted photon corresponds to a
Particular frequency of emitted radiation
Ephoton= hv
Bohr’s approach did not explain the spectra of atoms with
More than one electron
Other kinds of electromagnetic radiation
X Rays
Ultraviolet and infrared light
Microwaves
Radio waves
All forms of electromagnetic radiation move at a constant speed though a vacuum of
3.00 x 10^8 meters per second
3,00 x 10^8 m/s is also lights
Approximate speed through air
C
The mystery of the photoelectric effect invoked the
Frequency of the light striking the metal
Max Planck studied the emission of light by
Hot objects
Planck proposed that a hot object does not emit
Electromagnetic energy continuously
Planck suggested that the object emits energy in
Small specific packets called quanta
The energy of this photon is equal to the difference in
Energy between the atoms Initial state and its final state
Bohr calculated the allowed
Energy levels for the hydrogen atom
Bohr related the possible energy level changes to the
Lines in the hydrogen emission line spectrum
Bohr’s theory didn’t explain the chemical
Behavior of atoms
