Download Lecture Summary June 10th

Chemistry 102 Summary June 10th
Fundamental Laws
Law of conservation of mass: mass is neither created nor destroyed.
Law of definite proportion: a given compound always contains exactly the
same proportion of elements by mass.
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 Atomic Theory (1808)
(1) Each element is made up of tiny particles called atoms.
(2) The atoms of a given element are identical; the atoms of different
elements are different in some fundamental ways.
(3) Chemical compounds are formed when atoms of different
elements combine with each other. A given compound always
has the same relative numbers and types of atoms.
(4) Chemical reactions involve reorganization of atoms – changes in
the way they are bound together. The atoms themselves are not
changed in a chemical reaction.
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Dalton was incorrect in assuming the atom was the smallest
indivisible particle.
J.J. Thomson (1898-1903) postulated the plum pudding model –
diffuse cloud of positive charge with negative electrons embedded
randomly in it. See Figures 2.7-2.9.
Rutherford (1911) postulated a new model for the atom – the
nuclear atom.
Nuclear Atom
- Figure 2.13 b.
- Nucleus contains protons (same as electrons but opposite charge) and
neutrons (same as mass of protons but uncharged). The nucleus
contains most of the mass of the atom.
- Electrons are negatively charged and move about the nucleus.
- Different elements have different numbers of protons and electrons
which greatly effects how they interact with each other.
Mass number
13
Na
11
element symbol
Atomic number
-
number of protons = number of electrons
atomic number = number of protons
mass number = number of protons + number of neutrons
Isotope: atoms with the same number of protons but a different number
neutrons. Most elements contain a mixture of isotopes.
Periodic Table
-
The number above each element refers to the atomic number.
Separated into nonmetals and metals.
Metals:
Conduct electricity and heat very efficiently, are malleable
and ductile and generally have a lustrous appearance.
Metals tend to lose electrons to form cations.
Nonmetals: Nonmetals lack any physical properties that characterize
metals. Nonmetals tend to gain electrons to form anions or
form bonds with each other to create covalent bonds.
Groups:
Elements in verticals columns in periodic talbe – have similar
chemical properties.
Periods:
Horizontal rows of elements in periodic table.
Using the Periodic Table to Determine Stable Charges Elements Form
-
In general: Metals form Cations and Nonmetals form Anions.
Noble gases do not form stable ions
Elements in groups 1A-7A gain or lose electrons to get the same
number of electrons as the closest noble gas.
Metals in 1A, 2A, 3A form +1, +2 and +3 cations.
Nonmetals in 5A, 6A, 7A form -3, -2 and -1 anions.
Simple Molecule Formation
-
In general group 1A-7A elements react with each other to form
compounds in order to achieve the same number of electrons as
the closest noble gases.
They can do this in two ways: (a) form ionic compounds
(b) form covalent compounds
Ionic bonds:
Electrons are transferred from one species to another
forming oppositely charged ions. Ionic compounds can
consist of simple ions (Na+Cl- ) or polyatomic ions
(NH4NO3). See Table 2.5 for a list of polyatomic ions.
Ionic bonding represents the force of attraction
between oppositely charged ions. Examples: BaCl2,
MgS.
Covalent bonds: Electrons are shared between atoms in the molecule,
formed between nonmetals. Examples: Cl2, H2O.
How to determine formulas of ionic compounds:
(i)
(ii)
predict stable charge of various atoms.
determine ratio necessary to give a neutral compound.
Nomenclature Rules
General:
(a) The first element (or cation) in the compound is named first by using
the base name of the element (or cation).
(b) The second element (or anion) is named last using the base name with
a suffix (-ide,-ate, -ite)
Ionic Compounds:
(a) The cation is always written first, the anion is second. The cation is
usually a metal.
(b) The cations: (i) monoatomic metals: use base name of the metal.
(ii) transition metals: use base name of metal followed by
roman numeral indicating charge.
(iii) polyatomic cation, use name in Table 2.5.
(c) The anions: (i) monoatomic nonmetals: use the base name of the
nonmetal, then add –ide suffix.
(ii) polyatomic ions, use name in Table 2.5.
Covalent Compounds:
(a) The first element in the formula is named first using the base name.
(b) The second element is named like an anion (base name plus –ide
suffix).
(c) Use prefixes to denote numbers for first and second element.
(d) The prefix mono is never used for naming the first element in a formula.
(e) Avoid awkward pronounciations, e.g. CO = carbon monoxide, not
carbon monooxide.
(f) Know common names like H2O = water, NH3 = ammonia and C6H12O6 =
glucose.
To memorize:
- Table 2.5 – common polyatomic ions.
- Names of elements 1-36.
- Table 2.6 – prefixes.
- Tables 2.7 and 2.8 – names of common acids, also know HClO4 is
perchloric acid.