Unit 3 Flashcards
element
a substance that can’t be broken down into other substances by chemical methods
microscopic form - sometimes used to mean a single atom of that element
macroscopic form - other times used to mean a sample large enough to weigh on a balance
generic form - when we say human body contains sodium, doesn’t mean elemental sodium is present, rather atoms of some form of sodium; many r soluble
118 elements, 88 of which occur naturally
chemical symbols
used as abbreviations for element names
if 3 letters = unknown
Al
Aluminum
13
Ar
Argon
18
Ba
Barium
56
B
Boron
5
Br
Bromine
35
Ca
Calcium
20
C
Carbon
6
Cl
Chlorine
17
Cr
Chromium
24
Co
Cobalt
27
Cu
Copper (cuprum)
29
F
Fluorine
9
Au
Gold (aurum)
79
He
Helium
2
H
Hydrogen
1
I
Iodine
53
Fe
Iron (ferrum)
26
Pb
Lead (plumbum)
82
Li
Lithium
3
Mg
Magnesium
12
Mn
Manganese
25
Hg
Mercury (hydrargyrum)
80
Ne
Neon
10
Ni
Nickel
28
N
Nitrogen
7
O
Oxygen
8
P
Phosphorus
15
Pt
Platinum
78
K
Potassium (kallium)
19
Si
Silicon
14
Ag
Silver (argentium)
47
Na
Sodium (natrium)
11
Sr
Strontium
38
S
Sulfur
16
Ti
Titanium
22
Zn
Zinc
30
Dalton’s Atomic Theory
- Most natural materials are mixtures of pure substances.
- Pure substances are either elements or compounds
- law of constant composition
- Elements are made of atoms
- All atoms of a given element r identical
- the atoms of a given element r diff from those of any other element
- atoms of 1 element can combine with atoms of other elements to form compounds.
compounds
a distinct substance that is composed of the atoms of 2+ elements & always contains exactly the same relative masses of those elements
can be broken down into elements by chem methods
always has the same relative #’s & types of atoms
law of constant composition
a given compound always contains the same proportions (by mass) of the elements.
Ex: water always contains 8g of oxygen for each gram of hydrogen
atoms
tiny particles of which elements are made
indivisible in chem processes
not created/destroyed in chem reactions. reaction only changes the way the atoms r grouped together
chemical formula
expresses the type of atoms & #’s of each atom in a given compound
table salt = NaCl
water = H2O
chemical name
table salt = sodium chloride
electron
a negatively charged particle
located outside of nucleus in a negatively charged “cloud”
most of volume of atom
proton
a positively charged particle, same size of charge as an electron, but positive
neutron
a neutral particle w/ a mass relatively close to that of proton
nucleus
small dense center of atom
protons & neutrons
most of the mass of atom
why do diff atoms have diff chem properties?
the # & arragnement of the electrons
the space in which the electrons move accounts for most of the atomic volume. the electrons r the parts of the atoms that intermingle when atoms combine to for molecules. the # of electrons a given atom possesses greatly affects the way it can interact w/ other atoms
atomic number
the identity of an element is determined by this
the # of protons
isotopes
(of an element)
have the same # of protons, & therefore the same atomic #, but diff #’s of neutrons
mass number
the total # of protons & neutrons in an atom
used in naming to identify isotopes, such as Carbon-14 & Carbon-12
practical purpose of isotopes
Iodine-123 (half-life 13 hours) is the isotope of choice for nuclear medicine imaging of the thyroid gland, which naturally accumulates all iodine isotopes
metals
good conductors of heat & electricity
shiny
malleable
ductile
always form cations; tendency to lose electrons = a fundamental characteristic of metals
shiny
have luster
malleable
can be hammered into sheets
flattens/bends w/out shattering
ductile
can be drawn into wires
comparison of electron models
nonmetals
good insulators
dull appearance
most r gases/easily vaporized solids & liquids
solids r brittle
insulator
absorbs electricity
metalloids
exhibit some prop’s of both metals & nonmetals
groups
all elements in a group have similar chem prop’s
Group 1
Alkali Metals
Group 2
Alkaline Earth Metals
Groups 3-12
Transition Metals
Group 17
Halogens
Group 18
Noble Gases
diatomic molecules
cannot stand alone
2 atoms
hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, iodine
HINClBrOF
ions
the equal # of protons & electrons gives an atom a net zero charge
adding or removing an electron from a neutral atom will create a charged ion
always fromed by adding/removing electrons, not by changing the # of protons
cation
positive ion
when atom loses 1+ electrons
Na → Na+ + e-
named using name of the parent atom
Ex: Na+ is called the sodium ion
anion
negative ion
when an atom gains 1+ electrons
Cl + e- → Cl-
named by taking the root name of the atom & changing the ending (adding -ide)
common anion name changes
chlorine - chloride ion
flourine - flouride
bromine - bromide
iodine - iodide
oxygen + 2 electrons = oxide
sulfur + 2 electrons = sulfide
ion group charges
Group 1 metals - +1
Group 2 metals - +2
many Group 3-12 metals - multiple charges
Group 13 metals - +3
Group 16 atoms - -2
Group 17 atoms - -1
ionic compounds
whenever a compound is formed b/w a metal & non-metal, it can be expected to contain ions
usually formed when metals + nonmetals; when they react, the metal atoms tend to lose 1+ electrons, which r gained by the atoms of the nonmetals; the reactions tend to form compounds that contain metal cations & nonmetal anions
chem compounds must have net charge of 0 - must be cations & anions present; the # of cations & anions must result in net charge of zero
usually strong electrolytes & can be expected to dissociate completely in solution
rules for compound formula writing
the cation/metal/pos. is always written first
use subscripts to balance charges on compounds
brittle
shatters/cracks into small pieces when struck
strong electrolyte
a substance that separates into ions when dissolved in water
dissociation
the process in which ionic compounds separate into ions
molecular compounds
usually non-electrolytes & don’t dissociate to form ions
resulting solutions don’t conduct electricity
molecular acids
can partially/completely dissociate, depending on their strength
W
tungsten
74
