Download ATOMS, MOLECULES, AND IONS

ATOMS, MOLECULES, AND IONS
Atomic Theory of Matter
Modern atomic theory is based on the experimental work of many scientists over the course of many
th
years. Experimentation done as early as the 18 century resulted in generalizations which are
summarized in what are called “laws”.
Dalton’s Atomic Theory of Matter —
♦
♦
♦
♦
♦
Matter consists of individual atoms.
All atoms of a given chemical element are identical.
Different chemical elements have differing atoms of different mass.
Atoms are indestructible – they retain their identity in reactions.
Compounds are formed from a combination of elements in small whole number ratios.
The Law of Constant Composition — the relative kinds and numbers of atoms are constant for
a given compound. (e.g. water, H2 O, always contains
2 hydrogen atoms and 1 oxygen atom)
The Law of Conservation of Mass — during a chemical reaction, the total mass before
reaction is equal to the total mass after reaction.
N2 + 3 H 2 → 2 NH 3
34 g
34 g
The Law of Multiple Proportions — if two elements A and B combine to form more than one
compound, then the mass of B that combines with the
mass of A is a ratio of small whole numbers. (e.g. CO,
CO2 )
Modern View of Atomic Structure
Experiments by Thomson and Millikan confirmed the existence of electrons as the negatively charged
–19
particles within an atom. Electrons have a charge of e = 1.6021773 × 10
C and a mass of
–31
9.109390 × 10
kg. Later experiments by Rutherford determined that at the center of an atom is a
positively charged, compact, heavy nucleus. The charge on the atomic nucleus is +Ze (Z is the
atomic number of the atom). The fundamental unit of positive charge in the nucleus is the proton.
♦ Chemical identity of an atom is determined by the number of protons.
♦ The nucleus also contains neutral particles, neutrons, which are essential for the stability of the
nucleus. They contribute to the mass of the atom but have no charge.
Atomic Mass Units
Angstroms (Å)
Isotopes, Atomic Numbers, and Mass Numbers
Z=
N=
A=
Ex. 1
An isotope detected in a mass spectrometer has atomic number 82 and relative mass
205. Write the symbol for this isotope, and list the subatomic particles composing it.
The Periodic Table
Molecules and Molecular Compounds
Chemical Formulas
Empirical and Molecular Formulas
Empirical Formula
Molecular Formula
Ex. 2
From the following list, find the groups of compounds that have the same empirical
formula: C2H2, N2O4, C2H4, C6H6, NO2, C3H6, C4H8
Ions and Ionic Compounds
A cation results when an atom or molecule loses electrons (giving it a positive charge).
An anion results when an atom or molecule gains electrons (giving it a negative charge).
Ionic Charges and Ionic Compounds
Ex. 3
Predict formulas for compounds formed from
a.
Polonium (Po) and strontium (Sr)
2+
3–
b.
Mg
and PO4
c.
Gallium (Ga) and fluorine (F)
Naming Inorganic Compounds
Ionic Compounds
Cations
Anions
Ionic Compounds
Acids
Binary Molecular Compounds
Ex. 4
Many familiar substances have common, unsystematic names. For each of the
following, give the correct systematic name:
a.
saltpeter (KNO3)
b.
c.
d.
soda ash (Na2CO 3)
lime (CaO)
muriatic acid (HCl)
e.
Epsom salts (MgSO4)
f.
milk of magnesia (Mg(OH)2)
Nomenclature Rules for Polyatomic Ions
Polyatomic Oxoanions with Standard Names
Key Element
Formula
Nitrogen
NO3
NO2
SO4
Sulfur
nitrate ion
−
nitrite ion
2–
2–
−
HSO3
Phosphorus
PO4
sulfate ion
hydrogen sulfate ion
sulfite ion
hydrogen sulfite ion
−
HSO4
SO3
Name of Ion
−
3–
phosphate ion
hydrogen phosphate ion
dihydrogen phosphate ion
phosphite ion
HPO4
2–
H2 PO4
–
3–
PO3
2–
CO3
Carbon
HCO3
Chlorine
ClO4
ClO3
ClO2
carbonate ion
hydrogen carbonate ion
−
–
perchlorate ion
chlorate ion
chlorite ion
hypochlorite ion
–
–
–
ClO
Boron
BO3
3−
borate ion
Polyatomic Ions with Non-Standard Names
Key Element
Carbon
Formula
−
−
NH 4
2–
+
H3 O
hydronium ion
hydroxide ion
peroxide ion
superoxide ion
–
OH
O2
Metals
2–
–
MnO4
CrO4
oxalate ion
ammonium ion
+
O2
acetate ion
cyanide ion
C2 O4
Oxygen
–
C2 H3 O2 (CH3 COO )
CN
Nitrogen
Name of Ion
–
2–
Cr2 O7
2–
permanganate ion
chromate ion
dichromate ion
Names of Common Acids
Binary Acids
Oxoacids
Organic Acids
HF
hydrofluoric acid
HClO4
perchloric acid
HCOOH
formic acid
HCl
hydrochloric acid
HClO3
chloric acid
CH3 COOH
acetic acid
HBr
hydrobromic acid
HClO2
chlorous acid
C6 H5 COOH
benzoic acid
HI
hydroiodic acid
HClO
hypochlorous acid
HOOC–COOH
oxalic acid
HCN
hydrocyanic acid
H2 SO4 sulfuric acid
H2 S
hydrosulfuric acid
H2 SO3 sulfurous acid
HNO3
nitric acid
HNO2
nitrous acid
H3 PO4 phosphoric acid
H2 CO3 carbonic acid
Ex. 5
Ex. 6
Iodic acid has the molecular formula HIO3. Write the formulas for the following:
a.
the iodate anion
b.
the periodate anion
c.
the hypoiodite anion
d.
hypoiodous acid
e.
periodic acid
From the following list of elements – Ar, H, Ga, Al, Ca, Br, Ge, K, O – pick the one that
best fits each description; use each element only once:
a.
an alkali metal
b.
an alkaline earth metal
c.
a noble gas
d.
a halogen
e.
a metalloid
f.
a nonmetal listed in group IA
g.
a metal that forms a 3+ ion
h.
a nonmetal that forms a 2– ion
i.
an element that resembles aluminum