Diatomic Elements
Some elements cannot exist by themselves, even
when they are isolated from any other type of
atom.
Elements of this nature will combine with atoms of
the same element in order to be stable. There are
eight elements that form diatomic molecules:
Three Hints: “7 that make a 7 and hydrogen” or
“sneeze HNOF “ or “GEN-u-INE”
General Information
A chemical reaction is a process in which one or
more substances are converted into new
substances that have different physical and
chemical properties.
  In a chemical reaction, those substances present
before the reaction are called the reactants.
Substances produced in a chemical reaction are
called the products.
  A chemical reaction takes place when an atom
can find a more stable way to be joined to other
atoms.
 
Chemical Equations
Scientists represent chemical reactions in chemical
equations. Chemical equations can be in words or
in formulas.
  In writing equations, many times it is important to
know the state of the atom or molecule you are
working with.
  To show this, we use the following abbreviations:
–  (l) - liquid (g) - gaseous
(s) - solid (aq) - aqueous
 
 
Aqueous means dissolved in water.
Balancing Equations
In all reactions, the Law of Conservation of Matter
is adhered to. Therefore, we must have the same
number of atoms of each type of element on both
sides of the reaction.
  We accomplish this by placing necessary
coefficients in front of the atoms or molecules in
order to balance the number of each atom or group
on each side of the arrow.
 
Examples
Balance:
__ Cu (s) + __ HCl (aq) --> __ CuCl2 (aq) + __ H2 (g) __SrF2 (aq) + __ Cu3PO3 (aq) --> __ CuF (aq) + __ Sr3(PO3)2 (s) Balance:
Solid calcium is mixed with aqueous nickel (III) sulfate and
makes aqueous calcium sulfate and solid nickel.
Solid copper (II) oxide mixes with carbon dioxide gas
(CO2) to make solid copper (II) carbonate.
Examples
Balance:
__ Mg (s) + __ HI (aq) --> __ MgI2 (aq) + __ H2 (g) __NaF (aq) + __ Ag3P (s) --> __ Na3P (aq) + __ AgF (s) Balance:
Solid calcium is mixed with liquid water to make aqueous
calcium oxide and hydrogen gas.
Solid cobalt (III) chloride mixes with aqueous strontium
sulfide to make solid cobalt (III) sulfide and aqueous
strontium chloride.
Where do elements come from?
All the elements that we talk about have to come
from somewhere on the Earth:
Atmosphere: N2, O2, Ar, some water and CO2
Hydrosphere: Water, NaCl, and smaller amounts of
Mg, S, and Ca
Lithosphere - Crust: Silicates (Compounds of Si, O
and other metals), CaCO3, Fe2O3, PbS.
Lithosphere - Mantle: Silicates with Mg & Fe
Lithosphere - Core: Fe and Ni
Ores & Minerals
Very few elements are found uncombined in
nature. Exceptions would include Au, N, O,
Ag, Cu and noble gases
The remainder of elements are usually found
in ores, a naturally occurring rock that can
be mined profitably.
Within these ores are minerals, solid
compounds containing the elements of
interest.
Types of Reactions
In this chemistry course, we will focus on five basic
types of reactions:
1) Combination or Synthesis - two or more reactants
come together to form one product. Types of Reactions
2) Decomposition - a single compound is broken
down into two or more smaller compounds or
elements.
Types of Reactions
3) Combustion - reactions in which a hydrocarbon is
combined with O2 and burned to always form
carbon dioxide and water.
Oxidation & Reduction
The process by which a mineral is converted to
a pure element is called a reduction:
Ex: CuCl2 (s) ---> Cu (s) + Cl2 (g)
In a reduction, electrons are gained by an atom
or ion.
The process by which the metal is changed
back into a cation is called an oxidation:
Ex: 2 Cu (s) + O2 (g) ---> 2 CuO (s)
In an oxidation, electrons are lost by an atom or
ion.
Redox Reactions
When both happen at the same time, it is called a
redox reaction
EX: CuCl2 (aq) + Mg(s) ---> Cu (s) + MgCl2 (aq)
Which of the reactants listed above is the reducing
agent (source of electrons)?
Which of the reactants listed above is the
oxidizing agent (species removing e-)? Types of Reactions
4) Single Replacement - an uncombined element
displaces an element that is part of a compound.
Types of Reactions
5) Double Replacement or Metathesis - Atoms or
ions from two different compounds replace each
other.
Activity Series of Metals
The activity series is a
listing of metals in
order of their reactivity.
An element at the top of
the list would rather be
in a compound than as
an element.
This activity series
affects only single
replacement reactions.
Section 2B Review
Balancing
Balancing 2
Reaction
Types
Predicting
Products
Labs &
Activities
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