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CHEM 135: EXAM 1
What is atomic mass unit (amu)? |
-->1/12 the mass of an atom of carbon-12
-->In imprecise terms, one AMU is the average of the proton rest mass and the neutron rest mass
--> It's is used to express the relative masses of, and thereby differentiate between, various isotopes of elements |
What is matter? |
-->Anything that has mass and volume -the "stuff" of the universe
-->It can either be a pure substance or a mixture
-->Examples: books, planets, trees or people
|
What is pure substance? |
-->Substance that is composed of only one atom or molecule |
What is an element? |
-->A substance that cannot be chemically broken down into a simpler substances (AKA it's indivisible)
-->Example: Hydrogen |
What is a compound? |
-->A substance that this composed of two or more elements in a fixed definite proportion (AKA it can be more broken down)
-->Example: H20 |
Classification of compounds and elements |
-->The classification of elements includes elements that are either atomic or molecular
-->The classification of compounds there are either molecular or ionic |
What is a mixture? |
-->A substance that this composed of two or more different types of atoms or molecules that can be combined in variable proportions |
What is homogeneous mixture? |
-->A mixture in which the composition is the same throughout (AKA spaciously uniform) |
What is heterogeneous mixture? |
-->A mixture in which the composition varies from one region to another (AKA spaciously non-uniform) |
What are the three different states of matter |
-->solid, liquid, and gas
-->These states change from each phase because of an increased temperature |
What's a solid? |
-->When Ions or molecules are closely packed together.
-->They also have a stable, definite shape, and a definite volume.
-->Examples: Ice Cubes and diamonds |
What's a liquid? |
-->Ions or molecules packed about as closely as they do in solid matters but are free to move relative to each other.
-->They also have a stable, definite shape, and a definite volume.
-->Examples: Water and alcohol |
What's a gas? |
-->Ions or molecules have a great deal of space between them and are free to move relative to one another
-->They lack a definite shape or volume and conforms to the shape and volume of its container
-->Examples: Helium and nitrogen |
What is a property? |
-->the characteristics that describe how matter behaves. |
What is a physical property? |
-->Properties in-which the substance exhibits by itself without any interacting with another matter such as color, melting point, boiling point, density |
What is a chemical property? |
-->Properties in-which the matter shows as it interacts with, or transforms into, other matter such as flammability, corrosiveness, acid/base behavior; oxidizing agent or reducing agent |
What are the two physical properties |
--> Extensive and intensive |
What is an extensive physical property? |
-->They are properties that depend on the amount of matter being measured
-->Examples: mass, volume, and length |
What is an intensive physical property? |
-->They are properties that do not depend on the amount of the substance present (Think of independent and intensive both start with the prefix -int)
-->Examples: color, viscosity, melting point, boiling
point, ductility, malleability, DENSITY! |
Dalton's Atomic Theory |
-->All matter is made of atoms because they are indivisible and indestructible.
-->All atoms of a given element are identical in mass and properties
-->Compounds are formed by a combination of two or more different kinds of atoms.
-->A chemical reaction is a rearrangement of atoms. |
Law of conservation of mass |
-->During a chemical reaction, which is when one or more substances are converted into one or more different substances, matter is neither created nor destroyed |
Law of definite proportions |
-->All samples of a given compound, regardless of their source or how they were prepared, have the same proportions of their constituent elements (meaning that there is always a ratio) |
Law of the multiple proportions |
->when two elements combine with each other to form more than one compound, the weights of one element that combine with a fixed weight of the other are in a ratio of small whole numbers. |
Law of conservation of energy |
-->When energy can neither be created nor destroyed, it is transformed from one form to another. |
Millikan's Oil Drop Experiment |
-->An experiment performed by Robert Millikan to determined the size of the charge on an electron.
-->He also determined that there was a smallest 'unit' charge, or that charge is 'quantized'. |
Plum-pudding Model |
-->This model is composed of electrons surrounded by a soup of positive charge to balance the electrons' negative charges, like negatively charged "plums" surrounded by positively charged "pudding" .
-->The electrons (as we know them today) were thought to be positioned throughout the atom in rotating rings.
-->In this model the atom was also sometimes described to have a "cloud" of positive charge. |
Rutherford's Gold Foil Experiment |
-->This experiment shot alpha particles at a thin sheet of gold. It was found that a small percentage of the particles were deflected, while a majority passed through the sheet.
-->This caused Rutherford to conclude that the mass of an atom was concentrated at its center. It also proved that the Plum-Pudding Model was wrong .
|
What is the nuclear theory of the atom? |
-->Most of the atom's mass and all of its positive charge are contained in a small core called the nucleus
-->Most of the volume in an atom is empty space, throughout which tiny negatively charged electrons are dispersed
-->There are as many negatively charged electrons outside the nucleus as there are positively charged particules (AKA protons) with the nucleus, so that the atom is electrical neutral |
What's a proton? |
-->A positively charged subatomic particle found inside the nucleus's atom
-->it's equal to the electrons
-->It's also equal to the Atomic Number |
What's a neutron? |
--> A subatomic particle with no net electric charge found inside the nucleus's atom |
What's a electron? |
--> A negative charged subatomic particle found in the outer shell of the nucleus's atom
-->It's equal to the number of protons |
What's an atomic number |
It's the number that defines the element and that assigned an element name
-->They range from 1-116 in the periodic table
-->In diagrams it's symbol is Z |
What is the mass number |
-->The sum of the number of protons and neutrons in the atom
-->In diagrams it's symbol is A |
What's an isotope? |
-->One of two or more atoms of the same element with the same number of protons (meaning same Atomic number) but different number of neutrons (meaning different mass number) and consequently different masses |
Characteristics of isotopes |
-->All Isotopes of an element have the same chemical behavior
-->The number of isotopes for an element tends to increase with increasing Z.
-->Not all isotopes are stable! |
Ways you can write isotopes of elements or elements by themselves? |
->Having the chemical symbol (or just the element) followed by a dash mark and then the mass of the isotope or the element |
What is natural abundance? |
-->The percentage of each different isotope in a naturally occurring sample of a given element |
What is Atomic Mass? |
-->It's the weighted average of the masses of the individual isotopes. |
What is the Atomic Weight equation |
[(% of natural abundance of isotope 1)(mass of isotope 1)] + [(% of natural abundance of isotope 2)(mass of isotope 2)] + [(% of natural abundance of isotope 3)*(mass of isotope 3)] + .... |
What's a Mass Spectrometry? |
-->a powerful characterization method that identifies elements, isotopes, and compounds based on mass-to-charge ratios. |
Measuring Atomic Mass by Mass Spectrometry |
-->The atom is put into the gas phase
-->An Electron is removed to make the atom into an ion
-->The Ion is accelerated in an electric field and its path deflected by a magnetic field |
What's an ion? |
-->An atom or molecule with a net charge caused by the loss or gain of electrons |
What's an cation? |
->A positively charged ion (AKA an ion that has more number of protons than electrons)
-->The type of element that it does it for is a metal
-->tend to loose 1 or more e−
-->For many main group metals, the charge =
the group number |
What's an anion? |
-->A negative charged ion (AKA an ion that has more number of electrons than protons)
-->The type of element that it does it for is a non-metal
-->tend to gain 1 or more e−
For nonmetals, the charge = the group
number − 8 |
What's a unit? |
--> a quantity used to specify measurements, which are critical in chemistry. |
What are the two most common unit system? |
-->Metric system which is used in most of the world
-->English system which is used in the United States |
What is the International System of Units |
-->(AKA SI) A unit of measurement that is based on the metric system and it has seven base quantities assumed to be mutually independent |
What are the 7 Base quantity? |
--> length (in meters or m)
-->mass(in kilogram or kg)
-->time (in seconds to s)
-->electrical current (in ampere or A)
-->temperature (in kelvin or K)
-->Luminosity intensity (in candela or cd)
-->amount of a particular substance (in mole or mol) |
Which ones are you going to be using in class? |
-->mass, length, time, temperature and amount of a particular substance |
What is a mole? |
-->A unit defined as the amount of material containing Avogadro's number |
How do you convert between number of moles and number of Atoms and vice versa? |
->Converting Moles to Atoms:
# of moles[(Avogadro's number)/(1 mole)]=y atoms |
What is uncertainty? |
-->Scientific measurements are reported so that every digit is certain except the last one, which always estimated
-->No measurement can be made with absolute certainty |
What is a significant figure? |
-->indicate what is known about the accuracy and/or precision of a measurement or calculated value. |
What is accuracy? |
-->It refers to how close the measured value is to the actual value.
-->It also refers to the measure of the bias. |
What is precision? |
-->It refers to how close a series of measurements are to one another or how reproducible they are.
-->It also refers to the measure of the bias. |
What is a systematic error? |
--> the mean that would result from an infinite number of measurements of the same measurand carried out under repeatability conditions, minus a true value of the measurand. |
What is random error? |
-->the result of a measurement minus the mean that would result from an infinite number of measurements of the same measurand carried out under repeatability conditions. |
What is a deviation? |
deviation=the averages of all of the values---the measured values |
What is standard deviation? |
-->square each deviation, then take the average, then take square root! |
What are the basic rules for significant digits? |
-->All nonzero digits are significant
-->All zeroes between significant digits are significant
-->All zeroes which are both to the right of the decimal point and to the right of all non-zero significant digits are themselves significant. |
What's the rule of thumb for significant figures in addition or subtraction? |
-->the number of places after the decimal point in the result should be less than or equal to the number of decimal places in every term in the sum. |
What's the rule of thumb for significant figures in multiplication or division? |
-->the number of significant figures in the result should be equal to the number of significant digits in the least precise number (the number with the fewest significant digits given in the problem). |
How is the substance's volume calculated? |
-->It's measured in Liter, L, or cubic centimeter and it's determined by displacement or the geometry of the atom (for example length x width x height) |
What is density? |
-->The ratio of a substance's mass (m) to a substance's mass (m)
--> It is an intensive property - useful (somewhat for identification) |
How is the substance's mass calculated? |
--> It's measured in grams, g, and it's determined from balance |
What is an extensive property? |
-->Properties that depend on the amount of the matter present. |
What is an intensive property? |
->Properties that do not depend on the amount of the matter present. |
What is energy? |
-->The Capacity to do work
-->IT's SI Unit is Joules or (Kg[m^2/s^2]) |
What is work? |
-->It is force that is applied to an object moves that object. |
What is total energy? |
Kinetic energy + potential energy |
What is thermal energy |
->Energy that comes from heat |
What is Calorie? |
-->A Unit of energy that is defined as the amount of energy required to raise one gram of water |
What is Joule? |
-->It's the SI unit for energy and is equal to 1 (Kg[m^2/s^2]) |
What is an exothermic reaction? |
-->This is when the reaction's heat is released and energy is lost (meaning that the energy is negative) |
What is an endothermic reaction? |
-->This is when the reaction's heat is absorbed and energy is gained (meaning that the energy is positive) |
What is the quantum-mechanical model? |
-->A model that explains the behavior of absolutely small particles such as an electron or a photon |
What is light? |
->A form of electromagnetic radiation
-->Composed of perpendicular oscillating waves, one for the electric field and one for the magnetic field |
What is the speed of light? |
-->2.988X10^8 [m/s]
-->All electromagnetic waves move through space at the same constant speed |
What is electromagnetic radiation? |
-->Wave composed of oscillating electric and magnetic field i the perpendicular planes. |
What is frequency? |
-->For waves, the number of cycles (or complete wavelengths) that passes through a stationary point in a second
-->Calculated in Hertz (1/s)
-->Greek letter: ν and it means Nu |
The longer the wavelength... |
..the lower the frequency |
The shorter the wavelength... |
..the higher the frequency |
What is amplitude? |
-->The vertical height of a crest (or depth of a through) of a wave; a measure of wave intensity |
What is wavelength? |
-->The distance between adjacent crests of a wave
-->λ (greek for lambda) |
What is the equation for a wavelength? |
Energy=(hc)/(λ) |
Plank's Constant |
-->Energy is transferred in the direction of propagation
-->h = Planck's constant = 6.6262 x 10^-34 [J•s] |
Having a large ν means that you have a.... |
.......large Energy |
Having a large λ means that you have a.... |
....small Energy |
A packet of light is called a..... |
....photon or a quantum of light |
What's a photon? |
-->it's the smallest possible packet of electromagnetic radiation with an energy equal to plank's constant times the frequency |
What is the electromagnetic spectrum? |
the range of all possible frequencies of electromagnetic radiation |
What thing in the electromagnetic spectrum has the longest wavelength? |
Radio waves |
What thing in the electromagnetic spectrum has the shortest wavelength? |
Gamma rays |
Shorter wavelength or higher frequency light has.. |
...higher energy |
Visible light |
-->visible light (400 to 700 nm) comprises only a small fraction of all the wavelengths of light
-->High-energy electromagnetic radiation (e.g., UV, X-ray, gamma) can potentially damage biological molecules. |
What color in visible light has the shortest wavelength? |
-->Violet |
What color in visible light has the longest wavelength? |
-->Red |
What is Spectroscopic Observations? |
-->"Line Spectra" observed from gas discharge tubes containing different elements in gaseous state. |
What is an emission spectrum? |
-> spectrum of electromagnetic radiation emitted by a self-luminous source
-->Only certain wavelengths (colors) of light observed
-->This means that only certain energy transitions are possible |
What is the Bohr model? |
-->According to his model, each spectral line is produced when an electron falls from one stable orbit, or stationary state, to another of lower energy
-->The modern model of the atom is based on quantum mechanics.
-->The Bohr Model contains some errors, but it is important because it describes most of the accepted features of atomic theory
-->Unlike earlier models, the Bohr Model explains the Rydberg formula for the spectral emission lines of atomic hydrogen. |
What is Rydberg's formula? |
R = -2.18 X 10^-18 J
H=6.626 x 10^−34 J s
C=2.998 x 10^8 m s−1
n=principal energy level |
What is the de Broglie relation? |
->The observation that the wavelength of a particle is inversely proportional to it's momentum |
What's "quantum numbers"? |
->An atomic orbital is specified by three (integer) quantum numbers.
--> There are four quantum numbers |
What are the four quantum numbers? |
-->The Principal Quantum Number (symbol for this is n)
-->The Orbital Angular Momentum Quantum Number (symbol for this is l)
-->The Magnetic Quantum Number (symbol for this is ml (the l is in subscript))
-->The Spin quantum number (symbol for this is ms (the s is in subscript)) |
What's the Principle quantum number? |
-> The Energy Level (symbol for this is n)
-->Energies are defined as being "negative."
-->An electron's energy is lowered (made more negative) as a result of its interaction with the nucleus of the atom.
-->a positive integer = 1, 2, 3, . . .
--> It's the same as the Bohr's model only in that model it's called the "shell" number |
As n gets larger... |
..The energy difference between orbitals gets smaller and the energy of the orbital becomes greater (less negative) |
The Principle quantum number, n is equal to what? |
-->a positive integer
-->n= 1, 2, 3, . . . |
What is The Orbital Angular Momentum Quantum Number? |
->The Orbital Quantum Number (symbol for this is l)
-->It determines the shape of the suborbital
-->Each value of lis designated by a particular letter that designates the shape of the orbital. |
What is The Orbital Angular Momentum Quantum Number, l, equal to? |
-->positive integers from 0 to n-1 are allowed |
What are the suborbital? |
-->s
-->p
-->d
-->f |
Describe the "s" orbital |
-->It's when l = 0
-->the only value of ml is 0, which means there are only one suborbital.
-->the orbitals are spherical and have no specific or special orientation in space
-->The surface shown encloses the space occupied by an electron ~ 90% of the time.
-->orbitals are allowed in all shells (n = 1, 2, 3, . . .) |
Describe the "p" orbital |
->It's when l = 1
-->orbitals are like two balloons tied at the knots, meaning that they are in a dumbbell shape and are always perpendicularly in space
-->The values of ml are −1, 0, +1, which means there are three suborbital.
-->orbitals are allowed for n = 2, 3, . . . |
Describe the "d" orbital |
-->It's when l = 2
-->the orbitals are mainly like four balloons tied at the knots
--> the values of ml are −2, −1, 0, +1, +2, which means there are five d orbitals
-->orbitals are allowed for n = 3, 4, . . . |
Describe the "f" orbital |
-->It's when l = 3
-->The orbitals are mainly like eight balloons tied at the knots
-->the values of ml are -3, −2, −1, 0, +1, +2, +3, which means there are seven f orbitals.
-->orbitals are allowed for n = 4, 5, . . .
-->f orbital elements are beyond the scope of Chem 135 |
What is the Magnetic Quantum Number? |
->The Position or Orientation Quantum Number (symbol for this is ml (the l is in subscript))
-->It determines the number and orientation of the suborbital
--> The magnetic quantum number is an integer that specifies the orientation of the orbital.
--> The direction in space the orbital is aligned relative to the other orbitals
-->Gives the number of orbitals of a particular shape |
The Magnetic Quantum Number, ml, is equal to what? |
-->Values are integers from −lto +l, Including zero
-->so it can be zero, a negative integer, or a positive integer |
What's the The Electron Spin Quantum Number? |
-->It does not depend on another quantum number
-->It designates the direction of the electron spin and may have a spin of +1/2, represented by a spin up (↑), or -1/2, represented by ↓, represented by a spin up (↑).
-->Orbital diagrams use a square to represent each orbital and a half-arrow to represent each electron in the orbital.
-->Spins must cancel in an orbital.
|
What are paired spins? |
-->Paired meaning the two electrons in an orbital must have opposite spins (i.e. one with the magnetic field the other against the magnetic field). |
What's an orbital? |
-->Each set of n, l, and mldescribes one orbital
-->Orbitals with the same value of nare in the same principal energy level
-->Orbitals with the same values of nand l are said to be in the same sublevel (AKA the subshell) |
What's an orbital diagram? |
A diagram that gives info similar to an electron configuration but symbolizes an electron as an arrow in a box representing an orbital, with the arrow's direction denoting the electron's spin |
What is the Pauli Exclusion Principle? |
-->No two electrons in an atom may have the same set
of four quantum numbers.
-->Therefore, no orbital may have more than two electrons, and they must have opposite spins |
What is a rule of thumb for Energy Levels and Sublevels? |
->The number of sublevels within a level = n.
-->The number of orbitals within a sublevel = 2l+1
-->The number of orbitals in a level = n2. |
When an atom absorbs energy... |
an electron in a lower energy orbital is excited or promoted into a higher energy orbital |
When an atom releases energy.. |
an electron in a higher energy orbital is excited or promoted into a lower energy orbital |
What is change in energy equation? |
-->The energy of the final energy- the energy of the initial energy |
What is a periodic property? |
-->A property of an element that is predictable based on an element's position in the periodic table
-->Examples: density and radii of elements |
Why is Dmitri Ivanovich Mendeleev important? |
-->In 1869, Mendeleev noticed that certain groups of elements had similar properties.
-->He found that when elements were listed in order of increasing mass, these similar properties recurred in a periodic pattern.
-->To be periodic means to exhibit a repeating pattern. |
What is a periodic law? |
-->When the elements are arranged in order of increasing mass, certain sets of properties recur periodically. |
What is the format of the Modern Periodic Table? |
-->The elements are listed in order of increasing atomic number rather than increasing relative mass as they were in Mendeleev's periodic table.
-->Mendeleev's periodic law predicts pattern but does NOT explain why the patterns or similarity in properties occurs. |
What is referred to as periods in the periodic table? |
-->Rows of the table |
What is referred to as groups or a family in the periodic table? |
-->Columns in the table are referred to as groups or a family.
-->Elements in a group or family have similar properties. |
What is a main-group element? |
->One of the elements found in the or p block of the periodic table whose property tend to be predictable based on their position in the table |
How can the elements be classified? |
-->metals
-->non-metals
-->metalloids |
What are the characteristics of a metal? |
->Solids at room temperature, except Hg
-->Reflective surface
-->shiny
-->Conduct heat
-->Conduct electricity
-->Malleable (meaning that they can be shaped)
-->Ductile (meaning that they can be drawn or pulled into wires)
-->Lose electrons and form cations in reactions
-->About 75% of the elements are metals
-->They are located in the lower left on the table |
What are the characteristics of a non-metal? |
-->Found in all three states
-->Poor conductors of heat
-->Poor conductors of electricity
-->Solids are brittle
-->Gain electrons in reactions to become anions
-->Located in the Upper right on the table (except H) |
What are the characteristics of a metalloids? |
-->Show some properties of metals and some of nonmetals
-->Also known as semiconductors |