No numerical value (Not Specific)
Numerical value (Very Specific)
All certain digits plus one more
Exact numbers have an infinite number of significant figures. Can come from counting or by definition.
How reproducible a measurement is.
How close to a target value.
Based on freezing and boiling points of water.
Represents lack of all thermal energy, "Absolute Energy".
Pure substances and mixtures.
Matter with fixed compositions.
Cannot be decomposed to smaller components by chemical means.
Made from two or more elements. (Compounds can be broken down by chemical means into elements)
Two or more distinct substances. Can be homogeneous or heterogeneous. (Mixtures are not fixed compositions)
Those which can be measured without a change in the substance.
Cannot be measured without change in substance.
Refers to how much matter there is in a given object.
Refers to the force with which the object is attracted to gravity.
Transformations that alter the chemical compositions of substances.
When one substance is changed into two or more others.
Consist of two or more regions, called phases, that differ in properties.
Substance is not changed although appearance might.
Result in changes in the identity of composition of a substance.
Property depends on sample size.
Independent of sample size.
Tightly packed together, regular arrangement, definite shape, volume, cot compressible.
Particles in close contact, indefinite shape, free to flow, definite volume, hard to compress.
Takes shape of container, particles far apart, compressible.
The compactness of an object. D=M/V
Forms of Energy
Thermal(heat), chemical, electrical, radiation(light), nuclear, mechanical.
Energy of motion; depends on velocity and mass (momentum).
Energy of position.
The position of one atom to another.
The sum of potential and kinetic energy in a mechanical system.
Energy transferred between objects due to temperature differences.
High to low energy state. When you lose energy in a process.
Low to high energy state. Gaining energy in a process.
All matter is composed of atoms, which are bits of matter too small to be seen. Atoms cannot be further split into smaller portions. Based on philosophical reasoning, not scientific method.
Conservation of Mass
No loss or gain of mass in chemical reaction. Formulated clearly by Antoine Lavoisier in 1789, an initiator of modern chemistry.
Law of Definite Proportion
Compounds exist in fixed proportions of elements by mass. This observation was mad by French chemist Joseph Proust around 1800.
Created in early 1800s-
1) Chemical elements are made of atoms
2) The atoms of an element are identical in their masses
3) The masses of different elements have different masses
4) Atoms only combine in small, whole number ratios
5) Chemical change is due to atoms recombining in different combinations
Law of Multiple Proportions
When 2 elements form more than one compound.
Crystals with water molecules bound loosely
1) Did not explain how or why atoms combine in certain ratios
2) Did not account for the attractive forces existing between particles of matter
3) Did not hint at possible relationships between electricity and matter
Charge to mass ratio of electrons in 1879 using a cathode ray tube.
Millik Oil Drop Experiment
In 1907 it determined the charge and mass of electrons.
New atomic model in 1911. The gold foil experiment.
Discovered the neutron in 1932. Neutron named for lack of charge.
One of two or more atoms with the same atomic number but with different numbers of neutrons.
Law that states elements are arranged on the periodic table according to their atomic numbers and chemical properties.
-Solids at room temperature, exception mercury
-Wide range of chemical reactivity
-Properties very unlike metals
-Usually encountered in the form of compound with other elements
-Poor conductor of electricity (Exception carbon as graphite)
-Wide range of chemical reactivity
-Share properties of metals and non-metals
-Can have the appearance of a metal
-Can conduct electricity(poorly, semi-conductors)
-Resemble non-metals chemically and physically
Oxygen compounds make water alkaline.
Alkaline Earth Metals
Oxygen compounds not soluble in water and found in earth.
Comes from Greek words meaning "salt formers"
The forces that hold atoms together in compounds.
Results from atoms sharing electrons.
A collection of covalently bonded atoms.
Electrostatic attractions between ions.
Ionically bonded compounds.
A positive ion.
A negative ion.
A single charged atom.
An ion containing a number of covalently bonded atoms acting as a single charged unit.
Lowest whole-number ratio of each element in a compound.
Exact number of atoms of each element in a compound.
Naming Binary Ionic Compounds(Type I)
1.Name/write cation first, then anion.
2.Monatomic cation= Simply the name of the element
Naming Binary Ionic Compounds(Type II)
-Metals form more than one one cation
-Use Roman Numerals in name
Naming Binary Compounds(Type III)
-Compounds between two non-metals
-First element in the formula is named first
-Element further right on table is usually named second
-Second element is named as if it were an anion
-Use prefixes(Monoxide, dioxide)
Naming Ternary Compounds
-Use the name of metal ion and polyatomic, metal named first
Nonmetals surrounded by oxygen. They are polyatomic ions
Patterns in Oxyanion Nomenclature(Reference Table E)
-The most common ions end in -ate
-The one with one less oxygen ends in -ite
The one with two less oxygens has the prefix hypo- and suffix -ite
-The one with one extra oxygen has the prefix per- and suffix -ate
A. An unstable nucleus will decay spontaneously to form more stable products.
B.An unstable nucleus will give off particles when it decays.
C.The particles "radiate" out from the center of atomic decay. This is the origin of nuclear radiation.
A.The ratio of protons to neutrons determines nuclear stability.
B.The first 83 elements all have stable isotopes.
C.Elements after 83 have no stable isotopes(all isotopes are radioactive.)
D. Isotope of an element that decays easily is called a radioisotope.
A. Chemicals reactions involve electrons
B.Nuclear reactions involve a change in the nucleus where protons and neutrons reside.
C.When atomic nucleus of an element is changed to create another element...a transmutation has occurred.
-Atomic number decreases by 4
-# of protons decreases by 2
-# of neutrons decreases by 2
-Mass number decreases by 4
1.A neutron "turns into a proton" by emitting an electron
2.Occurs because there are not enough protons in the nucleus to be stable.
-Atomic number increases by 1
-# of protons increases by 1
-# of neutrons decreases by 1
-Mass number is unchanged
1.A proton will convert itself to a neutron by shedding its extra charge and emitting a charged positron.
2.A positron is like the electron emitted from t.he nucleus in Beta decay except with a positive charge.
-Atomic number decreases by one
-# of protons decreases by 1
-# of neutrons increases by 1
-Mass number is unchanged
1.Gamma rays give off large amounts of energy in high frequencies and short wavelengths.
2.Nuclei giving off alpha or beta particles will often leave the nucleus in an excited state.
3.Gamma rays are how the nucleus returns to a "ground state" by shedding large amounts of energy.
A.Each of theses types of decay can be represented by an equation when decay occurs.
B.The sum of mass numbers and atomic numbers on each side of the equation must be equal.
A.Natural transmutations result from an unstable ratio of neutrons and protons, so the nucleus changes.
B. Scientists have the ability to alter the nucleus of atoms by artificial transmutation.
C.Artificial transmutations are caused by making particles collide with nuclei of atoms.
-Collision of a charged particle(Like protons or alpha particles) with a nucleus.
-Collision of neutrons(uncharged particle) with nucleus.
Mass converted into energy. E=mc^2
Nuclear Fission as Fuel
Fissioning a radioactive material to cause chain reactions.
A.Small nuclei are fused together to form a heavier element.
B.High pressure and temperature (Like the Sun!)
C.Not controllable on Earth (yet)
D.Uncontrolled fusion is in an H bomb
Splitting a heavy nucleus into lighter nuclei.
A.Time for half of the unstable nuclei to decay is called "half-life".
B.The shorter the half-life, the more unstable it is.
C. n equals the number of half lives a substance goes through.
amount remaining= (1/2)^n (Starting amount)
How to Calculate Decay
a)n equals the number of half life
b)Amount remaining= mass(0.5)^n
How to Calculate the Original Amount
a)n equals number of half lives
b)original amount= Amount left*(1/2)^n
Radioactive isotopes that are absorbed just as regular isotopes are. They are used to detect how drugs are metabolized.
Waves or streams of photons. This can be described as a wave. This has electrical and magnetic components.
The distance between successive peaks.
The number of complete oscillations in 1 second.
Converting from Wavelength to Frequency
Speed of light= Wavelength x Frequency
Finding Energy of the Light
E=h x Frequency of light
What did Planck discover?
Energy absorbed or emitted by matter is quantized.
What does the spectrum of atoms that are excited by an electric discharge(heat) look like?
Atoms that are excited by an electric discharge emit narrow bands. This could not be explained by Rutherford's model.
The Bohr Model of the Atom
.Electron in hydrogen atom travels in a circular orbit
.Electron energy proportional to distance from nucleus
.Orbit(energy levels) are quantized
.Orbits identified by quantum number (n)
.Energy is absorbed to move electrons to higher levels
.Light is emitted when electrons return to their ground states
.The closer an electron is to the nucleus, the lower its energy
.Any electron excited to a higher energy level will return to the "ground state"
When there is a continuous unbroken distribution of light of all colors. This is formed when the light from an object that's been heated to a very high temperature is split by a prism and displayed on a screen.
Filling Bohr's atoms with electrons
.Each energy level(shell) can accommodate a different number of electrons
.Maximum number of electrons in a shell=2n^2
.Fill starting from the lowest energy level
Assessment of Bohr's model
.Bohr was first to propose quantized energy and primary quantum number"n"
.However, Bohr's model fails for atoms with more than one electron
Schrodinger and Quantum Model
.Small, rapidly moving particles can behave as waves
.Waves can be described using mathematical equations
.Electron as waves occupy three dimensional space
Extra "space" creates new sublevels for electrons, this space is called an orbital
A list of all the electrons in an atom.
.Electrons listed by which orbital they are in
.Shows the number of electrons in the outermost energy level: valence electrons
.Valence electrons determine
.Valence electrons found in the s and p orbitals
Orbitals with the same energy are filled one at a time with the electron spins aligned
Describe the coordinates of an electron.
Principle-n,size of the orbital
Angular-l, shape of the orbital
Magnetic-ml,orientation of orbital
Spin-ms, spin of the electron
Allowed Values of Quantum Numbers
l:all values from 0 to n-1
ml:all values +l to -l
Pauli Exclusion Principle
No two electrons can have the same 4 quantum numbers
Electrons which occupy the outer s and p sublevels
A way to show the valence electrons of representative elements
.Used dots to represent electrons
.All elements desire an octet of electrons
Periodicity of the Elements
.Properties of the elements vary periodically across the periodic table
.This correlates with electronic structure
Half the internuclear distance of two atoms of the same element.
.Related to the size of the principal energy level of an atom
.Increases as we move down in a group in the periodic table
Effective Nuclear Charge(Zeff)
The nuclear charge felt by outer electrons.
.Electrons in core shells provide shielding
.Electrons in the same orbitals do not shield each other well
Estimating Effective Nuclear Charge
z is the total number of protons
s equals the number of core electrons
The Energy needed to remove an electron from an element
Energy+M---> M(+) + e-
This is an endothermic process
Going across a row, it gets harder to remove an electron
Energy change when an electron is added to an element.
X(g) + e-(s) ---> X-(g)
Second electron affinity is always endothermic because putting a second electron in the same orbital requires more energy because of repulsion.
The force of attraction between atoms of a compound.
Transfer of electrons from metals to nonmetals.
Metal becomes positively charged, nonmetal becomes negatively charged.
Ratio of anion to cation.
Properties of Ionic Compounds
.Crystalline at room temperature
.High melting, brittle solids
.Non conducting as solids
.Conduct electricity in solution or molten state
Energy required to separate the ions from each other to form a cloud of ions in the gas phase.
This provides the stability of ionic compounds.
These are very endothermic.
This increases as ions get smaller and increases in charge.
Ionic Bond and Electronic Structure
Atoms transfer valence electrons.
.Atoms combine:gain or lose electrons
.Result is to acquire eight valence electrons
."Octet" rule (Exception-Hydrogen)
An atom's attraction for the electrons in a chemical bond.
Polarity of Chemical Bonds
Electrons are not always shared equally. You can predict this using electronegativity. If the difference in electronegativity is 1.7 or greater in an ionic compound the bond is polar. If the difference in electronegativity is 0.5-1.6 in a covalent compound the bond is polar.
Electrons are shared between atoms.
Atoms share one pair of electrons. Connect atoms with a solid line.
Atoms share four electrons. Connect atoms with two solid lines. Stronger and shorter than single bonds.
Atoms share six electrons. Connect atoms with three solid lines. Stronger and shorter than double bonds.
Coordinate Covalent Bonds
One atom does not contribute any electrons to the bond.
Formed from atoms able to form covalent bonds in three dimensions. Networks solids are not individual molecules, but interconnected structures.
.Metal atoms form a close-packed.regular arrangement (Metals are crystalline).
.The atoms lose their outer-shell electrons to become positive ions.
."Sea" of mobile electrons surrounding a "lattice" of positive ions.
.Lattice held together by the strong attractive forces between the mobile electrons and the positive ions.
.Metals are malleable and ductile.
Properties of Metals
.Good conductors of electricity
.Electrons free to move from metal atom to metal atom
.Metals have luster
.Metals are good conductors of heat (ping pong ball effect)
Steps for Making Lewis Structures for Molecules
.Count the valence electrons for all atoms
.If a complex ion, add one for anion, subtract one for cation
.Make a skeleton, least electronegative atom in center, as symmetrical as possible. HYDROGEN NEVER IN THE CENTER!
.Draw bonds to each outer atom (2e- each)
.Remaining valence electrons on outer atoms (except hydrogen), 6 each max
.Place any leftover valence electrons on the central atom
.Add in pairs from outer atoms to give central atom an octet, multiple bonds if necessary
.Assign formal charges
"Apparent" charge on each atom in a Lewis Structure.
FC of atom= #VE-(# of bonds+#unshared electrons)
The sum of formal charges must equal the charge of the molecule.
Exceptions to the Octet Rule
1. Hydrogen-Full valence shell has two electrons
2. Period 3 elements and higher can have more than an octet
3.Molecules with boron and beryllium can have less than an octet
4.Molecule with an odd number of electrons
Lewis Structure For Period 3 and Higher
Add electrons until the central atom's formal charge is zero or you have made two double bonds.
Resonance Structures occur when more than one valid Lewis Structure can be written for a particular molecule.
Significance of Resonance Structures
.In uncharged molecules, resonance lowers electron energies, more space
.Many polyatomic ions have resonance structures
.In such ions, the charge can be "spread out of more atoms" as a stabilizing effect
Resonance Structure Guidelines
.Atoms cannot change position, only electrons are shifted
.The number of valence electrons does not change
.Follow the octet rules
Valence Shell Electron Pair Repulsion (VSEPR)
.Predicts structures of molecules or polyatomic ions
.Bonds and Lone Pairs: regions of high electron density around the central atom
.Minimize repulsion between the valence electron pairs around the central atom
VSEPR Rules (For central atoms)
.Draw the Lewis Structure for the molecule or ion.
.Count the number of regions of high electron density. Bonds and unshared electron pairs.
.Double and triple bonds count only as one region of high electron density.
.If resonance structures, use one of the resonance structures.
Electron Pair (Cloud) Geometry
Bond angles determined by the bonding pairs and lone pairs.
Angles locked in by electron pair geometry. Shape of molecules determined by the total number of bonding electron clouds.
Valence Bond Theory
.Molecular bonds form when atomic orbitals overlap (covalent)
.Electrons in each of the overlapping orbitals are shared in a bond
Bonds formed by "head on" overlap of atomic orbitals each with an electron (covalent).
Bonds Formed by "side on" overlap of atomic orbitals each with one electron.
The quantities in chemistry.
Number of carbon atoms in exactly 12.00g of carbon.
.Formula mass refers to the mass of a compound (amu)
.Sum of the atomic masses by chemical formula
Gram Formula Mass and the Mole
.The mass in grams of one mole of a compound
.For molecules, this may also be referred to as the gram molecular mass or molar mass
.Trick: GFM=Formula mass expressed in grams
Percent Composition of an Element in a Compound
n x molar mass of element/molar mass of
compound X 100%
n is the number of moles in the element in 1 mole of the compound
Water molecules part of crystal structure of the ionic compound.
The volume of any mole of any gas at STP is 22.4 liters.
A Chemical Reaction
One or more reactants change into one or more products.
One or more simple substances combine to form a more complex structure.
Oxygen and a compound of C,H,O react t
A single reactant produces two or more products.
Single Displacement Reaction
An uncombined element that is part of a compound.