Ap Chemistry, Chapter Seven Vocabulary

1 PART TWO: THE STRUCTURE OF ATOMS AND MOLECULES Chapter Seven: Atomic Structure (Text from Chemistry and Chemical Reactivity, by Kotz, Treichel, and Weaver

Electromagnetic radiation: radiation, such as light, microwaves, radio signals, x-rays, etc. Wavelength (λ): the distance between successive crests or high points of a wave Frequency (ν): the number of waves that pass a given point in some unit of time, usually per second Hertz (s-1): a unit for frequency, 1 per second Amplitude: the maximum height of a wave Node: a point of zero amplitude, occurs at intervals of λ/2 Standing wave: a type of wave that has two or more points of no amplitude, which has a distance of λ/2 between consecutive nodes, and is only possible in certain wavelengths. It is useful in describing electrons in atoms. Quantization: Max Planck's idea that heated vibrating atoms give rise to electromagnetic radiation at only certain frequencies Photoelectric effect: the ejection of electrons when light strikes the surface of a metal Photons: the mass-less particles that make up light, whose energy is proportional to the frequency of the radiation Line emission spectrum: the specific wavelengths emitted by gas particles when they are excited. Each element has its own unique one. Rydberg equation: an equation developed by Johann Balmer and Johannes Rydberg from which it was possible to calculate the wavelength of the red, green, and blue lines in the visible emission spectrum of hydrogen atoms Principal quantum number (n): a unitless integer having values of 1, 2, 3, and so on. It defines the energy level of an electron Ground state: the state of an atom with its electrons in the lowest possible energy levels Excited state: the state of an atom without all its electrons in the lowest possible energy levels

2 PART TWO: THE STRUCTURE OF ATOMS AND MOLECULES Chapter Seven: Atomic Structure (Text from Chemistry and Chemical Reactivity, by Kotz, Treichel, and Weaver

Lyman series: a series of emission lines having energies in the ultraviolet region that arises from electrons moving from states with n>1 to the n=1 state Balmer series: the series of lines that have energies in the visible region that arises from electrons moving from states with n>2 to the lower state with n=2 Quantum mechanics/wave mechanics: a concept developed by Schrödinger based on the hypothesis that an electron in an atom can be described by equations for wave motion Wave-particle duality: the electron has properties of both a wave and a particle Uncertainty principle: it is impossible to fix both the position of an electron in an atom and its energy with any degree of certainty Wave functions: the solutions to the wave equations, which describe an electron as a wave Electron density: the probability of finding an electron within a given region of space Quantum numbers n, ℓ, and mℓ: integral numbers that are a vital part of Schrödinger's solution. They also define the energy states and orbitals available to the electron Electron cloud pictures: a picture depicting the position of an electron in a 1s orbital at 1-second intervals for several thousand seconds Surface density plot/radial distribution plot: a plot that depicts the probability of finding the electron at a given distance from the nucleus Nodal surface: an imaginary planar surface that slices through the nucleus, divides the region of electron density in half, and which has zero probability of having an electron