Chemistry Midyear Exam
atomic number
# of protons in nucleus of atom of element
Group 1A
*Alkali Metals* -solids (except hydrogen which is a nonmetal) -very reactive -soft -silvery white
Group 2A
*Alkaline Earth Metals* -solids -somewhat reactive -soft -silver -form strong bases
Cations and Anions (period trend)
*Cation*→smaller than atom -losing e⁻, decrease size *Anion*→larger than atom -gaining e⁻, increase size
Ionization energy (period trend)
*Down a group*→decreases -increase shielding, decrease effective nuclear charge -outer e⁻=weak attractions to nucleus and can be more easily removed *Across a period*→increases -decrease shielding, increase effective nuclear charge -outer e⁻=stronger attractions to nucleus and are not as easily removed
Electronegativity (period trend)
*Down a group*→decreases -increase shielding, decrease effective nuclear charge -weaker pull from nucleus and more difficult to draw in other e⁻ *Across a period*→increases -decrease shielding, increase effective nuclear charge -stronger pull from nucleus and more difficult to draw in other e⁻
Effective nuclear charge (period trend)
*Down a group*→decreases -more energy levels, shielding outer e⁻ from p⁺ *Across a period*→increases -more e⁻ added to same energy level=more attraction of e⁻ to p⁺
Atomic radius/ionic size (period trend)
*Down a group*→increases -energy levels added, atomic radii/ionic size increase *Across a period*→decreases -effective nuclear charge increases, drawing e⁻ into nucleus, and decreasing atomic radii/ionic size
Metallic reactivity (period trend)
*Down a group*→increases -ionization energy decreases so it becomes easier to lose an e⁻ and form a compound *Across a period*→decreases -ionization energy decreases so it becomes difficult to lose an e⁻ and form a compound
Shielding (period trend)
*Down a group*→increases -more energy levels shielding outer e⁻ from p⁺ in nucleus *Across a period*→constant -same energy level across period (only adding e⁻ to energy level, not adding energy level)
Group 7A
*Halogens* -nonmetals -reactive -all states of matter
Alpha radiation
*Identity:* helium-4 (particle) *Complete chem. symbol:* 4/2 He *Charge:* 2+ *Mass:* 4 amu *Penetrating power:* low (skin) *Effective shielding:* stopped by paper -mass # *decreases by 4* -atomic # *decreases by 2*
Gamma radiation
*Identity:* high energy radiation (non-particle) *Complete chem. symbol:* 0/0 γ *Charge:* 0 *Mass:* 0 *Penetrating power:* high (whole body) *Effective shielding:* incomplete; possibly by several inches/feet of lead/concrete -mass # *does not change* -atomic # *does not change*
Beta (negative radiation)
*Identity:* high speed electron (particle) *Complete chem. symbol:* 0/-1 e *Charge:* 1- *Mass:* 0 *Penetrating power:* medium (tissue) *Effective shielding:* stopped by clothing/thin layer of metal foil -mass # *does not change* -atomic # *increases by 1*
Group 8A
*Noble Gases* -nonmetals -gases -unreactive -odorless and colorless
transmutation reactions
-AKA nuclear or radioactive decay reactions -the conversion of one element to another through process of radioactive decay -discovered by Rutherford -follows Law of Cons. of Mass (balance mass # and atomic # of each side)
What is the difference between Bohr's and Schrondinger's models?
-Bohr=orbits, Schrodinger=orbitals -Bohr's gives more of a direct position than Schrodinger's -Schrodinger=mathematical
Antoine Lavoisier
-Law of Conservation of mass -1789
Joseph Proust
-Law of Constant Composition -1799
What is spent nuclear fuel?
-U-235 that is used and is no longer efficient in splitting atoms
How did Rutherford set up his Gold Foil Experiment?
-aimed beam of high-speed alpha particles at an extremely thin piece of gold foil -lead block limits radioactivity
What did Bohr propose relating to electrons?
-arrange in concentric circular paths (orbits) -have fixed energy (do not lose energy and cannot fall into the nucleus) -located in energy levels (region around the nucleus where the e⁻ is likely to be moving -to move from one energy level to another, an e⁻ must gain or lose the right amount of energy
Where does energy come from?
-associated with emmission of energy of specific wavelength from specific levels -electrons closer to nucleus are more stable, and thus have less energy
Erwin Schrodinger
-described the behavior of electrons in the atom (quantum mechanical model) -1926
electron spin (ms)
-describes spin of electron in orbital -2 possible spinning motions of electrons (clockwise, counterclockwise) -spin=value of +½ or −½
Henry Moseley
-determined the atomic number of the atoms of the elements -arranged the periodic table in order of increasing atomic number -1913
JJ Thompson
-discovered electrons (using cathode-ray tube) -plum pudding model of the atom -1897
E. Goldstein
-discovered proton using cathode-ray tube experiment -1886
Antoine Henri Becquerel
-discovered radioactivity using uranium -with help of Marie and Pierre Curie -1896
Dmitri Mendeleev
-discovered systematic, logical way to organize element (increasing atomic mass) -1871
James Chadwick
-discovered the neutron -1932
sublevels (l)
-each principal energy level has 1 or more sublevels -# of sublevels=principal energy level -letters=s,p,d,f *s<p<d<f*
orientation (ml)
-each sublevel (except s) has more than one orientation
inner transition metals
-electrons fill "f" orbitals -28 elements below PT -"f"-level holds up to 14 e- -lathanides and actinides
Robert A. Millikan
-found values for electrons charge (negative) and mass (1/1840 the mass of a hydrogen atom) -oil drop experiment -discovered mass to charge ratio -1916
What are the problems with fusion?
-high temps cannot be achieved -cannot be controlled -only "practical" use if hydrogen bomb
How is spent nuclear fuel stored temporarily?
-in pools of water at power plants
How is electricity generated in a nuclear power plant?
-in the form of heat -heat transforms liquid water to steam -steam drives turbine engine -heat controlled by cooling it with water
principal energy levels (n)
-indicates the energy level of the electrons in the atom -described by principle quantum numbers -1-7 -equal to the row number (period) on the periodic table -all atoms have diff. number of principal energy levels -higher energy level=further away the e⁻ is from nucleus
Marie and Pierre Curie
-isolated two radioactive elements (radium and polonium) -1896
Characteristics of metals
-luster/shine -solids at room temp (except mercury) -good conductors heat/elec -malleable and ductile (mostly)
quantum mechanical model
-mathematical model -e⁻ located in orbits within principal energy levels -predicts prob. of e⁻ locations and paths in e⁻ clouds
Results of Rutherford's Gold Foil Experiment?
-most of alpha particles passed through -foil scattered fraction of alpha particles in every direction -some particles completely changed direction -plum-pudding model=wrong -all positive charge and most of mass located in a nucleus -atom made up mostly of empty space
Pauli Exclusion Principle
-no 2 e⁻ in the same orbital can have the same spin -no 2 e⁻ can have the same 4 quantum numbers
Group 6A
-nonmetals
fusion
-nuclei combine to produce nucleus of greater mass -can take place sun and stars and in an hydrogen bomb -cannot be controlled (only whether or not it starts) -releases more energy than fission -takes place at temps of about 40 million °C
fission
-nucleus of atom splits into smaller fragments -can take place in a nuclear power plant and in an atomic bomb -can be controlled in a nuclear power plant -uncontrolled=instantaneous -chain reaction (2-3 neutrons produced that cause other reactions to occur) -release enourmous amounts of energy
Characteristics of nonmetals
-poor luster -poor conductors heat/elec -neither malleable nor ductile -many=gases at room temp -others are solids -bromine is liquid -varation of physical properties
Quantum numbers
-principle quantum number (n) -angular momentum quantum number (l) -magnetic quantum number (ml) -electron spin quantum number (ms)
Niels Bohr
-proposed that electrons are arranged in orbits around the nucleus -1913
Democritus
-proposed the existence of small particles called atoms -4th century BC
Shapes of orbitals
-s=spherical shape: 1 orbital, 2 e⁻ -p=dumbbell-shape: 3 orbitals, 6 e⁻ -d=complex shape:5 orbitals, 10 e⁻ -f=complex shape: 7 orbitals, 14 e⁻
How is spent nuclear fuel stored permanently?
-site that is far away from people, water and places with earthquakes -should be in area with stable gov't -stored underground
What are transition metals that have only 1 charge?
-zinc (Zn2+) -cadmiuium (Cd2+) -silver (Ag+)
representative elements
All "A" group elements on the periodic table (does not include transition metals)
Dalton's Second Postulate
All atoms of a given element are identical, but they are different from those of any other element -proposed by Dalton himself -proved false b/c isotopes (nuclei with same # of protons but diff. # of neutrons)
Dalton's Fourth Postulate
Atoms are neither broken nor changed into any other type in any chemical reaction -proposed by Lavoisier -proved false b/c nuclear decay converts one type of atom to another
Dalton's Third Postulate
Atoms combine in simple whole # ratios to form molecules (because they're unbreakable) -proposed by Proust (incorporates Law of Constant Composition) -proved true
ion
single atom or group of atoms that has a positive/negative charge
Law of Definite Proportions
states that in samples of any chemical compound, the masses of the elements are alwyas in the same porportions (ratio or percents) -created by Joseph Proust -AKA: Law of Constant Composition
electronegativity (definition)
tendency of atom to attract e⁻ when combining w/ other elements
How is a fission reaction triggered?
Bombarding fissionable isotope with neutrons
carbonate
CO₃²⁻
Dalton's First Postulate
Each element is composed of tiny, indivisible particles called atoms -proposed by Democritus -proved false b/c atoms can be divided into protons, neutrons, and electrons
Hund's Rule
For orbitals of the same energy, e⁻ with the same spin will singly occupy each orbital before pairing up
ionic size (definition)
distance b/w nucleus of ion and point up to which the nucleus has influence on its e⁻ cloud
atomic radius (definition)
distance between center of nucleus and outermost e⁻ -½ distance b/w nuclei of two like atoms when joined/ in a diatomic molecule
shielding (definition)
effect of inner energy levels in reducing strength of nuclear charge on e⁻ in outer energy level
valence electrons
elections in the outer most energy level of an atom -can be gained, lost or shared in covalent bonds (most atoms)
transition metals
elements in the middle of the table -"d"-block element (fill up "d" orbital) -hold up to 10 e-
ionization energy (definition)
energy required to remove e⁻ from gaseous state of atom
quantized energy
e⁻ exist in certain energy levels and cannot exist b/w them *proposed by Bohr*
period
horizontal row of elements in the periodic table
solar fusion
hydrogen nuclei fuse to make a helium nuclei
Law of Conservation of Mass
in the case of an unbalanced chemical equation, the mass of the reactants must equal the mass of the products -discovered by Antoine Lavoisier
Law of Conservation of Matter
matter cannot be created or destroyed in ordinary chemical/physical processes
Periodic law
natural law that states that the physical and chemical properties of elements are periodic functions of their atomic numbers
periodic law
natural law that states that the physical and chemical properties of the elements are periodic functions of their atomics #s
effective nuclear charge (definition)
positive nuclear charge that e⁻ experience from nucleus -depends on # of protons in nuclear (attraction) and # of other e⁻ in atom (repulsion)
metallic reactivity (definition)
rate at which a metal substance tends to undergo a chemical reaction
orbital
region of spaces which gives a probability of where the electrons are located -max of 2 electrons *95% accuracy*
How to calculate the percent composition of water
1) Calculate MM of anhydrate 2) Calculate MM of H2O 3) Calculate MM of hydrate 4) Find % comp. of water in hydrate (MM of H2O/MM of hydrate)
How to find the molar mass of a hydrate
1) Calculate the molar mass of the salt/anhydrate portion (ionic compound) 2) Calculate the mass of the water portion by multiplying the whole number * molar mass of water 3) Add step 1 and 2 to get the final molar mass of the hydrate
How to find formula of a hydrate
1) Find mass of salt of mass of water (depends on equation) 2) Convert mass of salt to moles using molar mass of salt 3) Convert mass of water to moles using molar mass of water 4) Determine ratio of moles of water to moles of salt to find formula of hydrate (step 3/step 2) -always round to a whole #
What are non-power uses of nuclear energy?
1) Medical imaging and treatment 2) Research
What are other uses of nuclear energy?
1) Nuclear weapons 2) Power submarines 3) Power spacecrafts 4) Power aircraft carriers
How is spent nuclear fuel disposed of?
1) separated from less hazardous material 2) radioactive sealed in steel cases (canisters)
When did Dalton create his atomic theory?
1803
When did Rutherford do his gold foil experiment?
1911
Aufbrau's Order
Must fill the lowest energy levels with electrons first
ammonium
NH₄⁻
nitrate
NO₃⁻
hydroxide
OH⁻
phosphate
PO₄³⁻
sulfate
SO₄²⁻
Ternary Ionic Compounds
an ionic compound that ibcludes polyatomic atoms
polyatomic ions
a group of covalently bonded atoms that carry a charge -e⁻ shared -consists of 2 or more atoms
hydrate
a substance combined chemically with water in a definite ratio
half-lives
the time it takes for half of the nuclei of a radioisotope sample to decay to product *equation=Ae=Ao * 0.5 ^ (t/t1/2)* -Ae=amount of radioactive sub. left -Ao original amount of radioactive sub. -t=elapsed time -t1/2=half life of radioactive sub.
group/family
vertical column of PT that contains elements with similar electron configurations
