Unit 2-Atoms, Molecules, and Ions Flashcards
Dalton’s Atomic Theory
- Matter is composed of atoms
- An element is composed entirely of ONE TYPE of atom
- A compound contains atoms of 2 or more different elements. The rel # of atoms of each element in a compound is always the same
- Atoms do not change identity in chem reactions; only the ways in which they are joined change
Atoms
the smallest units of an element that have all the properties of that element
The Law of Constant Composition
all samples of a PURE substance contain the same elements in the same proportion by mass
Law of Multiple Proportions
when the same elements from more than one compound, the mass of 1 element that combines with a fixed mass of a second element are in a ratio of small whole #s
Law of Conservation of Mass
there is No detectable change in mass when a chem reaction occurs
Rutherford’s conclusions
(study notes on experiment)
- a nucleus that is very small compared to the atom, has a high pos charge and contains most of the mass of the atom
- the remainder space is mostly empty and has electrons
- proton in nucleus, pos charged with equal magn to neg charge of electron (equal # of protons and electrons)
atomic # (z) =
of protons
mass # (A) =
sum of protons and neutrons
isotopes
atoms of an element whose nuclei contain diff #s of neutrons (same atomic #, diff mass #)
Symbol: A/z X
Ions
charged particles created from a atom gaining/losing e-
Charge= P+ - e-
cation
pos charge from losing e-
anion
neg charge from gaining e-
atomic mass
1/12 mass of one 12C atom
(atomic mass=mass #u)
mass spectrometer
used to measure the masses and abundance of isotopes
isotopic mass
mass (a) of a particular isotope
atomic mass
the weighted avg mass of the naturally occurring isotopes of the element
(atomic mass = decimal %(A)isotopic mass(A) + decimal %(B)isotopic mass(B) + …)
periodic table
arranges the elements with similar properties in same column
period
a horizontal row (inc #)
group (family)
vertical column containing chem similar elements (properties)
metal
- element that’s shiny and is a good electrical conductor.
- center and left side of table
nonmetal
- typically a nonconductor
- top right of table
metalloid
- has properties of both metals and nonmetals
- staircase sep metals and nonmetals
representative element
the elements in the A groups (1, 2, 13-18)
transition metals
elements in the B groups (3-12)
inner-transitional metals
2 rows of metals (Ianthanides and actinides) set at bottom of table
alkali metals
soft, reactive metals in 1A
alkaline earth metals
elements in groups 2A
Halogens (aka salt-formers)
reactive NONMETALS in group 7A (17)
Noble gases
the stable, largely inert gases in group 8A (18)
molecules
a combination of atoms joined so strongly that they behave as a single particle
diatomic
contains 2 atoms
homonuclear diatomic
contain 2 of same atoms (N2)
heteronuclear diatomic
contain 2 different atoms (NO)
elements
all atoms in molec are same (O2)
molec compounds
2 or more elements form a molec (H2O)
- typicalyl from nonmetals
molec formula
gives # of every type of atom in molec
structural formula
shows how the atoms are connected in molec
molecular mass
sum of atomic masses of all atoms present in the molec formula expressed in atomic mass units (u)
ionic compounds
composed of cations and anions forming a neutral species
- usually metal + nonmetal
- cation surrounded by anion or vice versa
empirical formula
uses the smallest whole # subscription to express the relative # of ions
- rel # of ions balance charges to zero
polyatomic ions
a group of atoms with a net charge that behaves as a single particle
formula mass of ionic compounds
the sum of the atomic masses of all atoms in the empirical formula of an ionic compound
chemical nomenclature
the organized system for naming compounds
naming ionic compounds
- cation then anion
monoatomic ions: - cation same
- anion = name + “ide”
naming transition metals
for metals that form 1+ cation, a roman numeral = charge of ion is shown in parenthesis following name of element
acids
a compound that produces hydrogen cations when dissolved in water
naming acids
anions ending in:
- “ide” are changed to “ic” and prefix “hydro” added along with “acid”
- “ate” are changed to “ic” and “acid” added
- “ite” are changed to “ous” and “acid” added
naming of molec (nonmetal) compounds
first element followed by second ending in “ide”
order of element names
- elements farther to left of table is first
- elements closer to bottom w/in group is first
- hydrogen is first when combined w/ 6A and 2A element; is second when combined w/ 1A-5A
- oxygen is second; except with flourine
numerical prefixes in molecular compound names
some elements form 1+ compound. Add numerical prefixes (mono-, di-, tri-, tetra-, penta-, hexa-) (mono usually omitted for first element).
- Ex: CO = carbon monoxide
hydrocarbons
organic compounds that contain only the elements hydrogen and carbon
alkanes
hydrocarbons with formula CnH2n+2
cycloalkanes
hydrocarbons with a ring of carbon atoms and formula CnH2n
functional groups
atoms or small groups of atoms that undergo characteristic reactions
- Alcohols = -OH
- Ethers= C-O-C
Alkane nomenclature
- suffix -ane with proper prefix (# carbon atoms):
one = meth-
two = eth-
three = prop-
four = but-
fix = pent-
six = hex-
(ex: CH4 = methane)
Cycloalkane nomenclature
alkane nomenclature + prefix “cyclo”
(Ex: cyclopropane)
substituent: alkyl group
alkane with one hydrocarbon removed
- base alkane name w/ “-yl” ending
substituent: halides
add “oro” ending
Properties of ionic compounds
- metals and nonmetals
- hard, brittle solids
- high melting point
Properties of molecular compounds
- metals
- some liquid/gas at room temperature
- low melting point
dissociation of ionic compounds
ionic compounds dissociate into individual cations and anions when dissolved in water
electolytes
a substance that forms ions in water solution
- conduct electricity
nonelectolytes
water and compounds that dissolve in water as neutral molecules
- do not conduct electricity
- MOST molecular compounds
