Chem 001 Chapters 4-6 – Flashcards
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How is the term photon related to quantum
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a quantum of light is actually one photon
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In Rutherford's gold foil experiment, alpha particles
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were deflected by the atomic nucleus
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Would you use a physical or conceptual model to describe the following: the brain, the mind, the solar system, and the beginning of the universe
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physical, conceptual, physical, conceptual
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The mass of an element is
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the sum of the protons and neutrons
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If an element has 18 protons and 20 neutrons and 18 electrons, which expression correctly identifies the element
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argon-38
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Since atoms are mostly empty space, why don't objects pass through one another
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The electrons on the atoms repel other electrons on other atoms when they get close
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Which of the following is not a form of electromagnetic radiation
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sound waves
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The cathode ray consists of
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negatively charged particles
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How are frequency and wavelength related
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the higher the frequency, the lower the wavelength
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A certain radioactive element has a half-life of one hour. If you start with a 1-g sample of the element at noon, how much of this same element will be left at 3 PM
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.125 gram
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If a material has a half-life of 24 hours, how long do you have to wait until the amount of radioisotope is 1/4 its original amount
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48 hours
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Which of the following types of radiation might be best for medicinal imaging
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Gamma radiation would be best because it penetrates best
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If carbon-14 is a beta emitter, what is the likely product of radioactive decay
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nitrogen-14
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How do fission plants work
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the heat from a nuclear reaction is used to produce steam that drives a turbine
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What is transmutation
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changing one element into another by adding or removing protons from the nucleus
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Which of the following statements about chain reactions is true
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A chain reaction will only take place when a critical mass of material has been assembled
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What is a rem
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a rem is a unit for measuring radiation exposure
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People who work around radioactivity wear film badges to monitor the amount of radiation that reaches their bodies. These badges consist of...these devices monitor
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Gamma radiation
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Radioactivity is a tendency for an element or a material to
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emit radiation
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Which of the following molecules contains a polar covalent bond
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H-F
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Why is metal shiny
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The loose electrons reflect most wavelengths of light
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The concept of a chemical bond is
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how two or more atoms are held together
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How many valence electrons does bromine (Br, atomic no. = 35) have
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7
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If a neutral atom loses one electron, what is the electrical charge of the atom
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+1
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Which of the following statements is true
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The valence shell gives us the electron dot structure
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Which of the following elements will most likely form an ion with a +2 charge
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Mg
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Which of the following best describes ionic bonding
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one atom giving up some of its electrons to another atom
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Which should be larger, the potassium atom, K, or the potassium ion, K⁺
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The potassium atom, K, with an additional shell of electrons is larger
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Which would you expect to have a higher melting point: sodium chloride, NaCl, or aluminum oxide
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The aluminum oxide has a higher melting point because of the greater charges of the ions, and hence the greater force of attractions between them
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Physical model
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a model of something very large or very small
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Conceptual model
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helps predict how a system behaves
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JJ Thomson
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amount of deflection is related to mass and charge Angle of Deflection is proportional to (charge of particle)/(mass of particle)
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Robert Millikan
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conducted the oil drop experiment Calculated the electric charge of a cathode particle and derived the particle's mass
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Electron
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the particle found in cathode rays
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Ernest Rutherford
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oversaw the gold-foil experiment Passed alpha particles through a thin gold foil and some alpha particles were deflected
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Atomic Model
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Nucleus is drawn at the center of atom and the electrons fill space around nucleus
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Protons
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positively charged particles in the nucleus
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Atomic number
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the number of protons an element contains
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Neutron
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discovered by James Chadwick in 1932 Same mass as proton with no charge
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Nucleons
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particles located in the nucleus
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Isotopes
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atoms with the same number of protons but different numbers of neutrons and exhibit different mass numbers Shows element, atomic number as a subscript and atomic mass as superscript
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Atomic mass
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total mass of atom (protons + neutrons)
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Electromagnetic waves
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oscillations of electric and magnetic fields
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Wavelength
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the distance between two crests of a wave
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Wave frequency
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measure of how rapidly waves oscillate
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Electromagnetic spectrum
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full range of frequencies and wavelengths
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Spectroscope
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an instrument used to observe colors
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Max Planck
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hypothesized that light energy quantized The total amount of energy must be equal to a multiple of a fundamental unit of energy
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Niels Bohr
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explained the atomic spectra using Planck's quantum hypothesis An electron has more potential energy when farther from the nucleus When an atom absorbs a photon of light, it is absorbing energy
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Bohr's planetary model
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electrons orbit the nucleus at certain intervals, similar to planets orbiting the sun
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Wave-particle duality
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idea that matter can behave as a wave or as a particle
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Energy level diagrams
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shows orbitals of similar energy together
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Periodic Trend
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gradual change a property across the periodic table
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Inner-shell shielding
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inner shell electrons reduce the attraction of the nucleus on outer shell electrons
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Effective nuclear charge
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reduced attraction the outer shell electrons experience
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Calculating Z
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nuclear charge minus the inner-shell electrons
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Atomic diameter trends
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atoms in the upper right of periodic table are smaller
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Smallest atoms have
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the most strongly held electrons
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Stable nuclei
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due to the ratio of protons to neutrons
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Unstable nuclei
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contains an "off balance" ratio of protons and neutrons and transforms the nucleus to a more stable composition
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Radioactive materials
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material containing unstable nuclei
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Radioactivity
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emitted high-energy particles and radiation from unstable nuclei
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Radioactive decay
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process of emitting radioactivity
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Alpha
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positive charge
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Alpha radiation
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releases a stream of alpha particles
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Alpha particle
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contains 2 protons and 2 neutrons and is the same as a helium nuclei with low penetrating power
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Beta
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negative charge
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Gamma
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no charge
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Gamma radiation
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high-frequency electromagnetic radiation
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Gamma particle
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pure energy with high penetrating power
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Radon-222
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common source of radiation
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Mutations
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alterations in genetic information contained in our cells
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Rems
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units of radiation
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Radioactive Tracers
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allow molecules to be traced due to radiation
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Medical imaging
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isotopes used for the diagnosis of internal disorders
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Strong nuclear forces
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very strong force between nucleons
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Neutrons act as
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nuclear cement Neutrons feel attraction but not repulsion because they do not have a charge Neutrons can decay to a proton and an electron
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Transmutation
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changing of one element to another by changing the number of protons
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Nuclear Equation for Alpha and Beta Particles
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Alpha: Helium with subscript 2 and superscript 4 Beta: electron with subscript -1 and superscript 0
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Changes in atomic number by each type of particle (alpha and beta) release
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Alpha: decrease by two Beta: increase by one
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Half-life
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the time required for half of the radioactive atoms to decay
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Carbon-14 Dating
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used to calculate the age of carbon-containing artifacts
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Half of C-14 decays in about
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5730 years
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Nuclear Fission
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splitting a large nucleus into smaller halves which releases energy
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Chain reaction
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when a product of one reaction begins the next reaction
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Nuclear Fission Reactors
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produces electrical energy from nuclear reactions
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Nuclear fuel
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U-238 mostly with about 3% U-235
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Control rods
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neutron-absorbing material
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Moderator
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slows the velocity of the neutrons
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Liquid
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transfers the heat from the reactor
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Radioactive waste
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by products of nuclear reaction
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Albert Einstein
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postulated that mass and energy are two sides of the same coin E=mc2
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Nuclear Fusion
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combining two light nuclei to form a larger nucleus Mass is lost during the fusion process and this lost mass is released as energy
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Thermonuclear Fusion
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fusion brought about by high temperatures
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Valence electrons
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outermost electrons of an atom
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Valence shell
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the outer shell containing electrons
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Electron-Dot Structure
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convenient notation showing the valence electrons
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Nonbonding electron pairs
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don't normally form bonds
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Unpaired electrons
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strong tendency to form bonds
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Electron spin
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causes of the electron pairing and spins clockwise and counterclockwise
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Ion
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atoms with a charge
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Positive charge
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cation
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Negative charge
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anion
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Ionic bond
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electric force of attraction between 2 oppositely charged ions
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Ionic compound
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compound of ions
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Ionic crystal
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3-dimensional arrangement of ions in an ionic compound
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Metallic bonds
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electrons are loosely held and easily dislodged
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Alloy
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2 or more metals held together with metallic bonding
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Native metal
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metal found pure in nature
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Ores
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geologic deposits containing high concentrations of metal-containing compounds
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Covalent bonds
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bond formed through sharing of valence electrons primarily in nonmetal pairings and hydrogen tends to form covalent bonds
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Covalent Compound
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substance held together by covalent bonds
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Bonding pairs of electrons in covalent bonds are
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shared between 2 atoms and can be represented by 2 dots or a line
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Diamond
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carbon covalent compound where each carbon is bound to 4 other carbons
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Multiple bonds
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when more than two electrons are shared Double bond: sharing of 4 electrons Triple bond: sharing of 6 electrons
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Covalent bonding in polyatomic ions
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comprised of covalent bonding and an overall charge
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Valence-shell electron-pair repulsion (VSEPR)
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electron pairs arrange so they are as far apart as possible
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Linear
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straight line of 3 atoms
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Bent
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a compound with one center atom and 2 outer atoms with a bent shape to accompany for nonbonding electron pairs that are pushed to one side
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Trigonal planar
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2-D triangle consisting of one center atom and 3 outer atoms
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Trigonal Pyramidal
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pyramid consisting of one center atom and 3 outer atoms with the center atom being raised to make it 3-D (kind of like a bent trigonal planar)
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Tetrahedral
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pyramid consisting of one center atom with 4 outer atoms (resembling trigonal pyramidal except there is another atom on top)
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Substituent atom
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an atom or a lone pair on the central atom
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Dipole
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Separation of charges
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Electronegativity
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ability of an atom to tug on bonding electrons
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Polar bond
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the two atoms differ in electronegativity which means there is an unequal sharing of electrons and it exhibits a dipole
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Nonpolar bond
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the two atoms have the same electronegativity meaning they equally share electrons and it isn't a dipole
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Water is
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polar
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Polar molecule can be thought of as sticky because
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the different charges are attracted to each other
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The stronger the interaction
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the higher boiling and melting points
