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Chapter 2

Terms in this set (55)

The Greeks explanation of chemical changes
Matter was composed of: fire, earth, water, and air. Considered if matter was continuous, divisible/composed of small particles.
Democritus
termed atomos to describe ultimate particles
Alchemy
turning cheap metal into gold, discovered mercury, sulfur, and antimony... learned how to prepare mineral acids
Robert Boyle
1st chemist, measured pressure and volume of gases, a substance was an element unless it could be broken down into two or more simpler substances, clung to alchemist views
Georg Stahl
suggested that phlogiston flowed out of burning material and stopped the burning by saturating the air
Joseph Priestly
discovered oxygen gas ("dephlogisticated air") to support vigorous combustion, low in phlogiston
Antoine Lavoisier
measurement is an essential operation of chem (same w/ Boyle). he weighed reactants and products of reactions to discover the law of conservation of mass
Law of conservation of mass
mass is neither created nor destroyed
Joseph Proust
showed that a given compound always contains exactly the same proportion of elements by mass
Law of definite proportion
principle of the constant composition of compounds
John Dalton
if elements were composed of tiny individual particles, a given compound should always contain the same combination of these atoms, the same relative masses of elements were always found in a given compound. worked with oxygen and hydrogen and noted their compound relative amounts
-gave water formula OH (H=1, O=8)
Law of multiple proportions
when two elements form a series of compounds, the ratios of the masses of the second element that combine with 1 gram of the first element can always be reduced to small whole numbers
Dalton's Model
1. each element is made up of tiny particles called atoms
2. atoms of a given element are identical; atoms of different elements are different in some fundamental way(s)
3. chemical compounds are formed when atoms combine with one another, given compound always has same relative numbers and types of atoms
4. chemical reactions involve reorganization of the atoms-changes in the way they are bound together. atoms themselves are not changed
Atomic masses
Dalton developed
Joseph Gay-Lussac
measured the volumes of gases that reacted with one another
Avagadro's hypothesis
at the same temp and pressure, equal volumes of different gases contain the same number of particles, distances between the particles in a gas are very great compared with the sizes of the particles, determined by the number of molecules present
Stumbling on hypothesis
only atoms of different elements could attract each other to form molecules, therefore diatomic atoms could not be made due to the lack of affinity
Stanislao Cannizzaro
1. Compounds contained whole numbers of atoms as Dalton postulated
2. Avagadro's hypothesis was correct

his work led to approximate values of the relative atomic masses
Cannizzaro
hydrogen gas consisted of H2, assigned the relative molecular mass of hydrogen to be 2. then compared the mass of 1 liter of a given gas with the mass of 1 liter of hydrogen gas
Relative mass of hydrogen
(percent hydrogen/100)*relative molecular mass
J.J. Thomson
studied electrical discharges in partially evacuated tubes called cathode-ray tubes.
when high voltage was applied to the tube, a cathode ray (emanated neg. electrode) produced that was repelled by neg. pole, soon to be known as electrons
charge-to-mass ratio
e/m= -1.76*10^8 C/g
e=charge of electrons in coulombs
m=electron mass in grams
plum pudding model
all atoms must contain electrons that are balanced out by positive charge... therefore there is a diffuse cloud of positive charge with the negative electrons embedded randomly in it
Robert Millikan
worked with charged oil drops to determine the magnitude of the electron charge
mass of electron
9.11*10^-31 kg
Ernest Rutherford
directed an alpha particle at a thin sheet of metal foil, predicted that the alpha particles should crash through the thin foil, making minor deflections. in reality, many were deflected/reflected. this could only be caused by a center of concentrated positive charge that contains most of the atoms mass, because the atom is mostly open space
nuclear atom
an atom with a dense center of positive charge and electrons moving around the nucleus at a distance that is large relative to the nuclear radius
proton
positive charge equal in magnitude to the electron's negative charge
neutrons
same mass as a proton but no charge
electron
constitue most of the atomic volume and "intermingle" when atoms combine to form molecules, greatly affects its ability to interact with other atoms
nucleus
small in size, high density, accounts for almost all of the atoms mass. since atoms have no net charge, the number of electrons must equal the number of protons.
isotope
atoms with the same number of protons but different numbers of neutrons
atomic number
number of protons
written as subscript (below)
mass number
total number of protons and neutrons
written as superscript (above)
chemical bonds
forces that hold atoms together in compounds
covalent bonds
share electrons resulting in molecules
chemical formula
symbols for the element are used to indicate the types of atoms present and subscripts are used to indicate the relative numbers of atoms
structural formula
individual bonds are shown (indicated by lines)
space-filling model
show relative sizes of the atoms and relative orientation of the molecule (individual molecules move around as independent units)
ball-and-stick models
physical representation of molecules
ion(ic bond)
an atom or group of atoms that has a net positive or negative charge, positive ion=cation, negative ion=anion, force of attraction between oppositely charged ions (polyatomic ions: many atom such as ammonium nitrate)
metals
efficient conduction of heat and electricity, malleability, ductility (pulled into wires), lustrous appearance, tend to lose electrons to form positive ions
nonmetals
tend to gain electrons to form anions in reactions with metals, bond to each other to form covalent bonds
groups/families
elements in the same vertical columns have similar chemical properties
alkali metals
very active elements that readily form ions with a 1+ charge when they react with non-metals
alkaline earth metals
form ions with a 2+ charge when they react with non-metals
halogens
all form diatomic molecules
noble gases
exist under normal conditions as monatomic gases and have little chemical reactivity
period
horizontal rows of elements
binary compounds (type I; ionic)
composed of a cation (written first in formula) and an anion, monatomic cation takes its name from the name of the element, monatomic anion takes the first part of its name then adds -ide. a type 1 BIC contains a metal that forms only one type of cation
binary compounds (type II; ionic)
the use of Roman numeral in a systematic name is required only in cases in which more than one ionic compound forms between a given pair of electrons, most commonly occurs with transition metals which often form more than one cation (the positive and negative charges must be balanced, represented through the roman numeral to indicate the charge)
polyatomic ions
refer to page 39, memorize!
oxyanions
atoms of a given element and different numbers of oxygen atoms. when there are two members, the name with the smaller number of oxygen atoms ends in -ite and the name of the larger one ends in -ate (hypo- and per- are also used)
binary covalent compounds
formed between two non-metals
1st name is elemental name
2nd name is same as if it were an anion yet prefixes are added to denote the numbers of atoms present
acids
produce a solution containing free H+ ions (protons), a molecule with one or more H+ ions attached to an anion
-if the anion does not contain oxygen, the acid is named with hydro- and -ic
-if anion contains oxygen, use root of anion with -ic or -ous (if anion ends in -ate, use -ic)
(if anion ends in -ite, use -ous)
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