chem
Dalton's Theory (5)
-atoms are indivisible -all atoms of an element are identical -atoms of different elements are different -atoms combine in fixed ratios to form compounds -atoms cannot be created or destroyed
molecular geometry (2 electrons around central atom)
0 lone pairs - linear 1 lone pair - bent 2 lone pairs - bent
molecular geometry (4 electrons around central atom)
0 lone pairs - tetrahedral
molecular geometry (3 electrons around central atom)
0 lone pairs - trigonal planear 1 lone pair - trigonal pyramid
Pressure unit conversions
1 atm = 101.325 kPa = 760 torr = 760 mm Hg
to find empirical formula of a compound from masses
1. divide all masses by molar mass 2. take the quotient of those and divide them by each other=x 3. resulting number is the ratio (1:x)
molar volume
22.4 L/mol
Avagadro's number
6.02 x 10^23
theory (5 things)
A hypothesis that has been tested with a significant amount of data -testable -falsifiable -supported by many observations -can explain observations -can be used to make predictions
pure substance
A sample of matter, either a single element or a single compound, that has definite chemical and physical properties
amorphous solid
A solid made up of particles that are not arranged in a regular pattern -rapid cooling -no long range order -compressible
scientific law (4 things)
A statement that describes what scientists expect to happen every time under a particular set of conditions -testable -falsifiable -supported by many observations -can be used to make predictions
Standard Temperature and Pressure (STP)
A temperature of 273 K and a pressure of 1.00 atm
Hypothesis (3 things)
A testable prediction -testable -falsifiable -can explain observations
isotopes
Atoms of the same element that have different numbers of neutrons
Plasma properties
Conductors of electricity, at extreme temperatures, low density fill space, high kinetic energy, cations
band theory
Electrons move among orbitals of different energies, electrons move freely among atoms (delocalized)
Rutherford
Gold foil experiment, discovered nucleus most of the mass is in the nucleus most of the atom is empty space
Democritus
Greek philosopher that said all matter is made of tiny particles called "atomos" or atoms
Which scientist provided a foundation for John Dalton's work on the atomic structure?
Joseph Proust
Gay-Lussac's Law
P1/T1=P2/T2
Combined Gas Law
P1V1/T1=P2V2/T2 (constant n) (n is moles of gas)
Boyle's Law
P1V1=P2V2
Ideal Gas Law
PV=nRT (R=.08206)
Thompson's Atomic Model
Plum pudding model - positive pudding sprinkled with negative electrons
What is the empirical formula for a compound if a sample contains 1.0 g of S and 1.5 g of O?
SO3
ionization energy
The amount of energy required to remove an electron from an atom in the gas phase
photoelectric effect
The emission of electrons when electromagnetic radiation, such as light, hits a material, developed by Einstein, refuted Rutherford's atomic model
electron domain geometry
The three-dimensional arrangement of the electron domains around an atom sp-linear sp^2-trigonal planear sp^3-tetrahedral
mode
The value that occurs most frequently in a given data set.
Charles' Law
V1/T1=V2/T2
Avogadro's Law
V1/n1=V2/n2
A piece of limestone erodes due to acid rain. This process can be best described as a a. slow chemical change. b. rapid chemical change. c. slow physical change. d. rapid physical change.
a
How was the work of Newlands similar to that of Mendeleev on the periodic table? a. They both arranged the elements in order of increasing atomic mass. b. They both arranged elements that had similar properties into groups. c. They both predicted the positions of undiscovered elements on the table. d. They both placed the relative atomic mass of each element on the table.
a
Which ion was formed by providing the second ionization energy to remove an electron? a. Ca2+ b. N3- c. Fe3+ d. S2-
a
Which step would help a student find the molecular formula of a compound from the empirical formula? a. Multiply the subscripts of the empirical formula by the value of the ratio of the molar mass of the compound to the empirical molar mass of the compound. b. Subtract the value of the ratio of the molar mass of the compound to the empirical molar mass of the compound from the subscripts of the empirical formula. c. Divide the subscripts of the empirical formula by the value of the ratio of the molar mass of the compound to the empirical molar mass of the compound. d. Add the value of the ratio of the molar mass of the compound to the empirical molar mass of the compound to the subscripts of the empirical formula.
a
polyatomic ion
a charged group of covalently bonded atoms that acts as a single unit
polar bond
a covalent bond in which electrons are shared unequally difference in electronegativity is > 0.5 has partial charges
nonpolar covalent bond
a covalent bond in which the electrons are shared equally by the two atoms difference in electronegativity is < 0.4
single bond
a covalent bond in which two atoms share one pair of electrons, demonstrated by a single line
sigma bond
a single covalent bond that is formed when an electron pair is shared by the direct overlap of bonding orbitals
London Dispersion Forces (LDF)
a temporary attractive force that results when the electrons in two adjacent atoms form temporary dipoles
long range order in crystals
arrangement of particles where they are order over many multiples of the average particle diameter
mean
average
Hydrogen reacts with an element to form a compound. Which element would have the most valence electrons available to react with hydrogen? a. oxygen b. chlorine c. neon d. nitrogen
b
What is the correct chronological order of scientists contributing to the modern periodic table? a. Lavoisier, Newlands, Moseley, Dobereiner, and Mendeleev b. Lavoisier, Dobereiner, Newlands, Mendeleev, and Moseley c. Moseley, Mendeleev, Newlands, Dobereiner, and Lavoisier
b
What is the number of valence electrons in cadmium (Cd)? a. 1 b. 2 c. 10 d. 12
b
Which information must be known about a compound to find the molecular formula from the empirical formula? a. density b. formula mass c. percent composition d. mole ratio
b
Which statement describes a step in the formation of an ionic bond? a. An attraction occurs between two ions that have the same charge. b. A metal atom forms a cation, and a nonmetal atom forms an anion. c. A more electronegative atom transfers electrons to a less electronegative atom. d. A metal pulls electrons from another metal and produces a force of attraction.
b
adding and subtracting scientific notation
bases must be the same, the same number of decimal places as the least precise value
dipole-induced dipole forces
between polar and nonpolar molecules polar molecules induce charge redistribution in nonpolar molecule
Lattice energy is an estimate of the...
bond strength
ionic bonds
brittle, high melting/boiling point, conducts electricity when in water/molten or in liquid or gas state, forms by one atom stealing an electron from another atom, weaker than covalent
covalent bonds
brittle, low melting point, gas or liquid at room temp, very strong bonds
What happens to ions during bonding to form an ionic compound? a. Cations accept electrons and anions give away electrons. b. Anions and cations share electrons. c. Cations give away electrons and anions accept those electrons.
c
What is the best reason for a student to remove a dangling bracelet when heating test tubes of acidic solutions in a hot-water bath in a chemistry lab? a. to avoid reactions of the metal with gases in the lab b. to reduce the risk of burns from heat conducted through the metal c. to minimize the chance the bracelet pulling over a test tube, causing a spill d. to prevent misreading the temperature of the bath on a thermometer
c
Which property is better explained by the band theory than by the sea-of-electrons model? a. ductility b. thermal conductivity c. luster d. electrical conductivity
c
Which statement describes a major drawback of the Bohr model that caused scientists to replace it? a. It worked only for helium and larger atoms. b. It did not identify the distance between an electron and the nucleus. c. It contradicted the Heisenberg uncertainty principle. d. It stated that spectral lines of atoms are similar.
c
Immisable liquids
cannot dissolve in each other
properties of hydrogen bonds
causes high melting/boiling points because more energy is needed to separate molecules, high surface tension and viscosity, water: solid is less dense than liquid
Solids properties
conductivity depends on the material, high density, fixed shape, low kinetic energy, neutral, cations, or anions
ionic bonds form...
crystals
An investigation involves determining which metal is better for making pots that will cook food faster. Which is the best hypothesis to use for this investigation? a. Copper is better than iron for making pots. b. Copper is more malleable and heats up faster than iron. c. If copper is a better conductor, it will heat up faster than iron. d. If copper heats up faster than iron, it is better for making pots.
d
Members of which group easily lose an electron to form a +1 cation? a. halogens b. alkaline earth metals c. noble gases d. alkali metals
d
Which of the following metal atoms would have the highest conductivity? a. the atom with the smallest radius and the fewest valence electrons b. the atom with the smallest radius and the most valence electrons c. the atom with the largest radius and the fewest valence electrons d. the atom with the largest radius and the most valence electrons
d
electron affinity trends
decreases down a group, increases across a period
electronegativity trends
decreases down a group, increases across a period
ionization energy trend
decreases down a group, increases across a period
Millikan's Atomic Model
discovered the charge on an electron
electron sea model
electrons move freely among atoms (delocalized), electrons all have approximately the same energy
intramolecular forces v. intermolecular forces
forces within molecules (like covalent bonds) v. forces between molecules, a lot weaker
Deposition
gas to solid
accuracy
how close a measured value is to an accepted value
naming acids
hydro- + base name of nonmetal + -ic + acid
Increase in altitude
increase in pressure cooler=slower=hits walls less=less pressure (or opposite)
atomic radii trends
increases down a group, decreases across a period
ionic radii trends
increases down a group, decreases across a period (deceases for cations and then anions but anions are larger because they gain electrons)
naming bases
ionic: cation metal + hydroxide covalent: naming is based on number attached to N ・ammonia (NH3) ・primary amine ・secondary, tertiary, etc
emmisable liquid
liquids dissolve each other
Kinetic Molecular Theory (KMT)
matter is constantly moving in constant, random motion all collisions are elastic
Electron Cloud Model
model of atom in which the electrons seem to form a cloud as they move around the nucleus, explains the probable location of electrons (not specific)
Bohr Model
model of the atom in which electrons move rapidly around the nucleus in paths called orbits, in order for the electrons to change orbits they must absorb or release energy, doesn't explain that higher orbits have lower energies and electrons exist between orbits.
covalent bonds form...
molecules
expanded octect
more than eight valence electrons can be used in bonding
how to find mass from molecules
number of molecules/6.02 x 10^23=x x*molar mass=mass (g)
emission lines
occur when the electrons of an excited atom, element or molecule move from a lower energy level (higher orbital) to a higher energy level (lower orbital)
median
order the data points and find the middle value of the set
pi bonds
overlap of p-orbitals allows additional sharing
Precision
reproducibility of a measured value
Why are pressure and volume inversely proportional?
smaller volume-> more collisions-> higher pressure
formula unit
smallest repeating unit of an ionic compound
Sublimation
solid to gas
dipole-dipole interactions
strongest van der waal force, between polar molecules positive pole attracts negative pole
electronegativity
the ability of an atom to attract electrons from another atom in a compound
electron affinity
the energy associated with the addition of an electron to a gaseous atom
hydrogen bonding
the intermolecular force in which there is an attraction between H bonded to an electronegative atom (usually O, N, or F) and a electronegative atom of another molecule
vapor pressure
the pressure exerted by a gas over a liquid, higher vapor pressure, the easier it is to have the liquid boil
van der Waals forces
the two weakest intermolecular attractions- dispersion interactions and dipole forces
Properties of London Dispersion forces
usually nonpolar molecules but sometimes polar heavier molecule=stronger force usually gases weakest van der waal force
octet rule
when valence shells are filled they are more stable (so have 8 electrons, also not always true) exception example: H only needs 2 to be stable