Topic 2 (incomplete) Flashcards
ELEMENT
Consists of only 1 type of atom
- Unique physical & chemical properties
- Cannot be separated into a simpler
type of matter
o MOLECULE
- A structure that consists of 2 or more
atoms that are chemically bound
together - E.g. H2O, CO2, O2 , N2, H2
- Note: O2 , N2, and H2 always exist as
diatomic molecules in nature
o MOLECULE
- A structure that consists of 2 or more
atoms that are chemically bound
together - E.g. H2O, CO2, O2 , N2, H2
- Note: O2 , N2, and H2 always exist as
diatomic molecules in nature
COMPOUND
A substance composed of 2 or more
different elements which are chemically
bound together
- Properties differ from that of constituent
elements
- Fixed composition (w.r.t. mass and
number of atoms of different elements)
o MIXTURE
A group of 2 or more elements and/or
compounds (components) that are
physically combined
- Retain their original properties
- E.g. NaCl + H2O or benzene + toluene
DIFFERENCE BETWEEN AN ELEMENT, A
MOLECULE AND A COMPOUND:
- An element consists of only 1 kind of atom
(E.g. Ne, Fe, Hg, etc.) - A molecule is a substance that consists of 2 or
more atoms that are chemically bound
together
(E.g. H2O, CO2, O2 , N2, H2, etc.) - A compound is a molecule composed of 2 or
more different elements which are chemically
bound together
(E.g. H2O, NH3, CO2, etc.)
Heterogeneous mixture
- Visible boundaries between components
o Homogeneous mixture
- No visible boundaries because components are
mixed as individual atoms, ions and molecules - Also called a solution
- Solutions exist in all 3 phases
The distinction between mixtures and compounds
Physically mixed → can be separated by physical
means; in this case by a magnet
- Chemically reacted → cannot be separated by physical
Typical separation processes:
- Evaporation
- Distillation
- Filtration
- Precipitation
- Centrifugation etc
Expressing component amounts in a compound or
mixture as:
- A percentage (sum of individual components adds up to 100%)
- A fraction (sum of fractions adds up to 1)
LAW OF MASS CONSERVATION
Mass is conserved during a chemical reaction.
o Each molecule in a compound has its elements in the same proportions
by mass (e.g. CO2 has 1 parts C by mass + 2 parts O by mass).
o The total mass remains unchanged because the atoms of the reactants
are just rearranged into products.
Principle of mass conservation:
Matter cannot be created nor destroyed.
o The total mass of substances does not change.
o MASS IN = MASS OUT
Principle of mass conservation:
Matter cannot be created nor destroyed.
o The total mass of substances does not change.
o MASS IN = MASS OUT
DALTON’S ATOMIC THEORY, What does it explain
the conservation of mass…
DALTON’S ATOMIC THEORY
All matter consists of atoms
- Atoms of one element cannot be converted to
atoms of another element
- Atoms of an element have the same number of p+
and e-
, which determine the chemical properties of
an element
- Compounds form through chemical bonding of 2 or
more elements in specific proportions.
- Since every atom has a fixed mass, and during a
chemical reaction atoms are combined, there is no
mass change overall.
Mass spectroscopy → determines
atomic mass
* Atomic mass is calculated as the average of the masses of its
commonly occurring isotopes weighted according to their natural
abundance. (therefore not integers on periodic table)
Atomic mass = SUM (isotopic mass) (fractional abundance)
1 amu =
1/12 of the mass of a carbon -12 atom
POLYATOMIC BONDING
o 2 or more covalently bonded
atoms with a resultant charge
(positive or negative)
IONIC COMPOUNDS – WITH MONATOMIC IONS
Transitional elements with monoantomic ions. What are the systematic names and the common names
Transitional elements with monoantomic ions. What are the systematic names and the common names
What does the ous or ic after the monotomic ions mean?
ous → lower charge
- ic → higher charge
Polyatomic ions
