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CHEM 115: Exam 1
Law of Conservation of Mass
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In a chemical reaction, matter is neither created or destroyed.
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Law of Definite Proportions
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All samples of a given compound, regardless of their source or how they were prepared, have the same proportions of their constituent elements.
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Law of Multiple Proportions
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When two elements (call then A and B) form two different compounds, the masses of element B that combine with 1 g of element A can be expressed as a ratio of small whole numbers.
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Atomic Theory
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The theory that each element is composed of tiny indestructible particles called atoms, that all atoms of a given element have the same mass and other properties, and the atoms combine in simple, whole-number ratios to form a compound.
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Cathode Rays
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A stream of electrons produced when a high electrical voltage is applied between two electrodes within a partially evacuated tube.
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Electrical Charge
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This is a fundamental property of some of the particles that compose atoms, and it results in attractive and repulsive forces.
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Electron
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A negative charged, low mass particle present with in all atoms.
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Protons
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Positively charged particles within the nucleus, so that the atom is electrically neutral.
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Neutrons
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Neutral particles within the nucleus, that's mass is similar to a proton.
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Atomic Mass Unit
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Defined as 1/12 the mass of a carbon atom containing six protons and six neutrons.
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Atomic Number
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The number of protons in an atom's nucleus and is given the symbol Z.
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Chemical Symbol
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Each element, identified by its unique atomic number, is represented with this.
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Isotopes
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Atoms with the same number of protons but different numbers of neutrons.
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Natural Abundance
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The percentages of the isotopes are called this.
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Mass Number
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The sum of the number of neutrons and protons and is represented by the symbol A.
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Ions
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An atom that loses or gains electrons.
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Cations
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Positively charged ions.
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Anions
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Negatively charged ions.
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Metals
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Lie on the lower left side and middle of the periodic table and share some common properties: they are good conductors, malleable, typically shiny and ductile, and tend to lose an electron in a chemical changes.
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Nonmetals
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Lie on the upper right side of the periodic table and share common properties; poor conductors, tend to gain electrons when they undergo chemical changes and some are solids at room temperature and others are gases and liquids.
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Metalloids
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Many lie along the zigzag diagonal line that divides meals and nonmetals and exhibit mixed properties.
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Semiconductors
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Some metalloids are classified as this because of there intermediate (and highly temperature dependent) electrical conductivity.
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Main-Group Elements
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Those elements found in the s or p blocks of the periodic table, whose properties tend to be based on their position in the periodic table.
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Transition Elements (Transition Metals)
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Those elements found in the d block of the periodic table whose properties tend to be less predictable based on their position on he periodic table.
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Group (Family)
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Each column within the main-group regions if the periodic table. Elements in the same column tend to have similar properties.
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Noble Gases
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The group of elements in A8 and are mostly unreactive.
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Alkali Metals
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The group of elements in 1A elements and are ALL reactive metals.
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Alkaline Earth Metals
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The group of elements in 2A are FAIRLY reactive.
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Halogens
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The group of elements in 7A are very reactive nonmetals.
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Atomic Mass
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The calculated average mass for each element.
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Mass Spectrometry
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The masses of atoms and the percent of abundance of isotopes of elements are measured using this.
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Avogadro's Number
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The number of ^12C atoms in exactly 12 g of ^12C; equal to 6.0221421X10^23 atoms. (With sigfigs 6.022X10^23 atoms)
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Molar Mass
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The mass of 1 mol of atoms of an element.
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Thermochemistry
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The study of relationships between chemistry and energy.
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Heat
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The flow of energy caused by temperature difference.
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Kinetic Energy
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The energy associated with motion of an object.
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Thermal Energy
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The energy associated with the temperature of an object.
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Potential Energy
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The energy associated with the position or composition of an object.
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Chemical Energy
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The energy associated with the relative position of electrons and nuclei in atoms and molecules, is also a for of potential energy.
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Law of Conservation of Energy
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Energy can be neither created nor destroyed.
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System
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In thermodynamics, the portion of the universe which is singled out for investigation.
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Surroundings
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In thermodynamics, everything in the universe which exists outside the system under investigation.
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Electromagnetic Radiation
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A type of energy embodied in oscillating energy and magnetic field.
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Of a wave is the vertical height of a crest ( of depth of a trough).
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Of a wave is the vertical height of a crest ( of depth of a trough).
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Wavelength
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Of a wave is the distance between adjacent crests ( or any two analogous points) and is measured in units such as meters, micrometers, and nanometers. Symbol is λ in equations.
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Frequency
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The number of cycles (or wave crests) that pass through a stationary point in a given period of time. Symbol looks like a slanted v.
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Quantum Mechanical Model
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A model that explains how electron exist in atoms and how those electrons determine the chemical and physical properties of elements.
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Electromagnetic Spectrum
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All wavelengths of electromagnetic radiation.
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Constructive Interference
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The interaction of wave from two sources that align with overlapping crests, resulting in a wave of greater amplitude.
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Destructive Interference
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The interaction of waves from two sources aligned so that the crest of one overlaps the trough of the other, resulting in cancellation.
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Diffraction
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When a wave encounters an obstacle or a slit that is comparable to the size to it's wavelength, it bends around it.
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Photoelectric Effect
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The observation of many metals emit electrons when light shines upon them.
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Photon (Quantum)
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A packet of light.
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Emission Spectrum
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The range of wavelengths emitted by a particular element; used to identify the element.
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Heisenberg's Uncertainty Principle
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The principle stating that due to the wave-particle duality, it is fundamentally impossible to precisely determine both the velocity of a particle at a given moment in time.
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Deterministic
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A characteristic of the classical laws of motion, which imply that present circumstances determine future events.
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Indeterminacy
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The principle that presents circumstances do not necessarily determine future events in the quantum-mechanical realm.
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Orbital
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A probability distribution map showing where the electron is likely to be found.
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Quantum Number
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One of four interrelated numbers that determine the shape and energy of orbitals, as specified by a solution of the schrodinger equation.
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Principle Quantum Number
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An integer that specifies the overall size and energy of an orbital. The higher the quantum number (n), the greater the average distance between the electron and the nucleus and the higher its energy.
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Angular Momentum Quantum Number
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An integer that determines the shape of an orbital. (l)
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Magnetic Quantum Number
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An integer that specifies the orientation of an orbital. (ml)
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Radial Distribution Function
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This represents the total probability of finding the electron within a thin spherical shell at a distance r from the nucleus.
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Node
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A point where a wave function (ψ), and therefore the probability density (ψ^2) and radial distribution function, all go through zero.
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Phase
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The sign of the amplitude wave-positive or negative-is known as this.
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Principle Levels (Principle Shells)
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Orbitals with the same value of n are said to be in the same ________.
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Sublevel (Subshell)
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Orbitals with the same value of n and l are said to be in the same _________.
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Probability Density
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The probability (per unit volume) of finding the electron at a point in a space as expressed by a three-dimensional plot of the wave function squared (ψ^2).
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Periodic Property
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A property of an element that is predictable based on an element's position in the periodic table.
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Electron Configuration
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Shows the particular orbitals that are occupied for that atom.
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Ground State
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The lowest energy state of an atom.
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Electron Spin
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In orbital diagrams, the direction of the arrow (pointing up or pointing down) represents this.
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Spin Quantum Number
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The spin of an electron specified by a fourth quantum number (ms)
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Pauli Exclusion Principle
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No two electrons in an atom can have the same four quantum numbers.
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Coulomb's Law
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The potential energy (E) of two charged particles depends on their charges (q1 and q2) and on their separation (r).
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Shielding
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The effect on an electron of repulsion by electrons in lower-energy orbitals that screen it from the full effects of nuclear charge.
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Effective Nuclear Charge
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The actual nuclear charge experienced by an electron, defined as the charge of the nucleus plus the charge of the shielding electron.
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Penetration
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When an outer electron goes into the region occupied by the inner electrons, it experiences a greater nuclear charge and therefore (according to Coulomb's law) as lower energy.
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Hund's Rule
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When filling degenerate orbital's electrons fill them singly first, with parallel spins.
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Valence Electrons
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For main group elements, the valence electrons are those in the outermost principal energy level.
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Core Electron
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Those electrons in a complete principle energy level and those in complete d and f sublevels.
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