The height of a wave's crest above its centerline, which is related to the intensity or brightness of light, is called the amplitude.
Missing Word
amplitude
Amplitude is the size of a wave's displacement from its center. For light, a larger amplitude means greater intensity, while the color depends on wavelength.
Category: Electromagnetic Radiation
Question 2
A single particle of light, whose energy equals hν (the constant h times the frequency), is called a photon.
Missing Word
photon
A photon is a particle of electromagnetic radiation. Its energy, E = hν, depends only on frequency, which explains why light below a threshold frequency cannot eject electrons from a metal.
Category: Electromagnetic Radiation
Question 3
The SI unit of frequency, equal to one cycle per second, is the hertz.
Missing Word
hertz
The hertz (Hz) is one cycle per second, or s^-1. Visible light has frequencies of a few hundred trillion hertz.
Category: Electromagnetic Radiation
Question 4
The bending and spreading of a wave as it passes an edge or travels through a narrow opening is called diffraction.
Missing Word
diffraction
Diffraction is a characteristic behavior of waves. The observation that beams of electrons also diffract was key evidence that matter has wave properties.
Category: Electromagnetic Radiation
Question 5
The region of the electromagnetic spectrum with wavelengths just shorter than those of visible violet light is called ultraviolet.
Missing Word
ultraviolet
Ultraviolet radiation lies just past the violet end of the visible spectrum, with shorter wavelengths and more energetic photons than visible light. Those higher-energy photons are what cause sunburn.
Category: Electromagnetic Radiation
Question 6
The constant h, equal to 6.626 × 10^-34 J·s and relating the energy of radiation to its frequency, is named for the physicist Max Planck.
Missing Word
Planck
Planck's constant is the proportionality constant in E = hν. Max Planck introduced it when he proposed that energy is absorbed and emitted in fixed quanta.
Category: Quantum Theory
Question 7
The model of the hydrogen atom in which the electron moves in circular orbits of fixed, quantized energy is named for Niels Bohr.
Missing Word
Bohr
Niels Bohr proposed in 1913 that the hydrogen electron can occupy only certain orbits with specific energies. His model explained the hydrogen line spectrum but failed for atoms with more than one electron.
Category: Bohr Model
Question 8
The empirical equation that predicts the wavelengths of all the series of lines in the hydrogen emission spectrum is named for Johannes Rydberg.
Missing Word
Rydberg
Johannes Rydberg generalized earlier work into one equation that gives the wavelength of every hydrogen spectral line from two integers. Bohr's model later explained why the equation works.
Category: Bohr Model
Question 9
A surface or point in an orbital where the probability of finding the electron is zero is called a node.
Missing Word
node
A node is a place where the electron's wavefunction, and so its probability density, equals zero. Orbitals with higher values of n have more nodes.
Category: Quantum Numbers and Orbitals
Question 10
The fourth quantum number, ms, which can be +1/2 or -1/2, describes an electron property called spin.
Missing Word
spin
Spin is an intrinsic property of the electron that makes it behave like a tiny magnet, with two possible orientations. Two electrons sharing an orbital must have opposite values of ms.
Category: Quantum Numbers and Orbitals
Question 11
Orbitals that have exactly the same energy, such as the three 2p orbitals of an isolated atom, are described as degenerate.
Missing Word
degenerate
Degenerate orbitals are orbitals of equal energy. In a given atom, all the orbitals of one subshell, such as the five 3d orbitals, are degenerate.
Category: Quantum Numbers and Orbitals
Question 12
In period 4, the first element whose ground-state atom has an electron in a 3d orbital is scandium.
Missing Word
scandium
Scandium, atomic number 21, has the configuration [Ar] 4s2 3d1. After the 4s subshell fills at calcium, the next electrons enter 3d, so scandium begins the first row of transition metals.
Category: Electron Configurations
Question 13
A p subshell can hold a maximum of 6 electrons.
Missing Word
6
A p subshell has three orbitals, and each orbital holds up to two electrons, so the subshell holds 6. This is why the p block of the periodic table is six columns wide.
Category: Quantum Numbers and Orbitals
Question 14
Species such as Na+, F- and O2- that have the same number of electrons and the same electron configuration are described as isoelectronic.
Missing Word
isoelectronic
Isoelectronic species share the same electron count and configuration; Na+, F- and O2- all have the configuration of neon. Within such a series, the ion with more protons is smaller.
Category: Periodic Trends
Question 15
An ion formed when an atom gains one or more electrons, and which is larger than its parent atom, is called an anion.
Missing Word
anion
An anion is a negatively charged ion. Adding electrons increases electron-electron repulsion while the nuclear charge stays the same, so the anion is larger than the neutral atom.
Category: Periodic Trends