Chapter 7 - Atomic Structure and Periodicity Flashcards
electromagnetic radiation
radiant energy that exhibits wavelike behavior and travels through space as the speed of light in a vacuum
wavelength
the distance between two consecutive peaks or troughs in a wave
frequency
the number of waves (cycles) per second that pass a given point in space
Planck’s constant
the constant relating the change in energy for a system to the frequency for a system to the frequency of the electromagnetic radiation absorbed or emitted; equal to 6.626x10^-34 J x s
quantized
the concept that energy can occur only in discrete quanta
photons
a quantum of electromagnetic radiation
dual nature of light
the statement that light exhibits both wave and particulate properties
diffraction
the scattering of light from a regal array of points or lines, producing constructive and destructive interference
photoelectric effect
the phenomenon in which electrons are emitted from the surface of a metal when light strikes it
diffraction pattern
the distinctive pattern of light and dark fringes, rings, or spots formed when waves, such as X-rays or electrons, interact with a periodic structure (like a crystal lattice) and interfere with each other, revealing information about the structure’s arrangement
continuous spectrum
a spectrum that exhibits all the wavelengths of visible light
line spectrum
a spectrum showing only certain discrete wavelengths
quantum model
Bohr proposed that the electron in a hydrogen atom moves around the nucleus only in certain allowed circular orbits
ground state
the lowest possible energy of an atom or molecule
standing wave
a stationary wave as on a string of a musical instrument; in the wave mechanical model, the electron in the hydrogen atom is considered to be a standing wave
wave function
a function of the coordinates of an electrons position in three-dimensional space that describes the properties of the electron
orbital
a specific wave function for an electron in an atom. the square of this function gives the probability distribution for the electron
quantum (wave) mechanical model
a model for the hydrogen atom in which the electron is assumed to behave as a standing wave
Heisenberg uncertainty principle
a principle stating that there is a fundamental limitation to how precisely both the position and the momentum of a particle can be known at a given time
probability distribution
the square of the wave function indicating the probability of finding an electron at a particular point in space
radial probability distribution
when the total probability of finding the electron in each spherical shell is plotted versus the distance from the nucleus, the plot is obtained
quantum numbers
When we solve the Schrödinger equation for the hydrogen atom, we find many wave functions (orbitals) that satisfy it. Each of these orbitals is characterized by a series of numbers called quantum numbers, which describe various properties of the orbital:
The principal quantum number has integral values: . The principal quantum number is related to the size and energy of the orbital. As increases, the orbital becomes larger and the electron spends more time farther from the nucleus. An increase in also means higher energy, because the electron is less tightly bound to the nucleus, and the energy is less negative.
The angular momentum quantum number has integral values from to for each value of . This quantum number is related to the shape of atomic orbitals. The value of for a particular orbital is commonly assigned a letter: is called ; is called ; is called ; is called . This system arises from early spectral studies and is summarized in Table 7.1
principal quantum number (n)
the quantum number relating to the size and energy of an orbital; it can have any positive integer value.
