1. A chemical reaction occurs when the chemical bonds in molecules are broken and new bonds are formed, creating new substances. This can happen through various processes, including atoms or ions gaining, losing, or sharing electrons to achieve stable electron configurations. 2. Examples of chemical reactions include rusting of steel which combines iron and oxygen, or the mixing of hydrogen and oxygen gases which produces an explosive reaction to form water. 3. Many chemical reactions occur as part of larger reaction sequences, such as the multiple steps that plants use in photosynthesis to ultimately produce glucose molecules from carbon dioxide and water.

1. HOW CHEMICAL REACTION
OCCURS
Michelle Arden B. Tarifa

2. Reactions occur when
two or more molecules
interact and the
molecules change.
Bonds between atoms
are broken and created

3. A chemical reaction is a
process that leads to the
transformation of one set
of chemical substances to
another. Classically, chemical
reactions encompass changes
that only involve the positions
of electrons in the forming and

4. with no change to the nuclei (no
change to the elements present),
and can often be described by
a chemical equation. Nuclear
chemistryis a sub-discipline of
chemistry that involves the
chemical reactions of unstable
and radioactive elements where

5. Chemical reactions happen
around us all the time. Some
happen all by themselves -
like when plants use
photosynthesis to chemically
change energy from the sun
into food. People also cause
chemical reactions to

6. Cooking food and burning
fuel cause chemical
reactions. A chemical
reaction is a process when
one or more substances
are changed into other
substances

7. Electrons surround the nucleus
of an atom in layers called
shells. The first shell, closest to
the nucleus, is full with only two
electrons. The second shell is
full with eight electrons, and the
third shell will also hold eight
electrons. For the most stable

8. To get a full shell, atoms will
take electrons from other
atoms; give up electrons to
other atoms, or share
electrons with another atom.
When this happens, a
chemical reaction has taken
place, and a chemical bond

9. To better understand this, let's
look at the sodium atom.
Sodium has eleven electrons. Its
first shell is full with two
electrons, and its second shell is
full with eight more electrons,
making ten electrons. But since
sodium has eleven electrons, it

10.  To become more stable, sodium will
easily give up that one electron so it
will have a full shell. The extra
electron will go to another atom that
needs one electron to have a full
shell. Chlorine is a good example.
Chlorine has seventeen electrons:
two in the first shell, eight in the
second shell, and seven in the third

11. To be stable, chlorine needs
to pick up another electron.
It can take one electron from
sodium. This forms a bond
between the atoms of sodium
and chlorine. A new
compound, sodium chloride,
or table salt, has been made.

12.  1. A chemical change must occur. You
start with one molecule and turn it into
another. Chemical bonds are made or
broken in order to create a new
molecule. One example of a chemical
reaction is the rusting of a steel garbage
can. That rusting happens because the
iron (Fe) in the metal combines with
oxygen (O2) in the atmosphere. Chemical
bonds are created and destroyed to

13.  When a refrigerator or air
conditioner cools the air, there is no
reaction in the air molecules. The
change in temperature is a physical
change. When you melt an ice
cube, it is a physical change. When
you put bleach in the washing
machine to clean your clothes, a
chemical change breaks up the

14.  2. A reaction could include
atoms, ions, compounds, or
molecules of a single
element. You need to remember
that a chemical reaction can
happen with anything, just as long
as a chemical change occurs. If you
put pure hydrogen gas (H2) and
pure oxygen gas in a room, they

15.  If you were to add a spark, those
gases would be involved in a violent
chemical reaction that would result
in a huge explosion (exothermic).
Another chemical reaction might
include silver ions (Ag+). If you mix a
solution with silver ions with a
solution that has chloride (Cl-) ions,
silver chloride (AgCl) precipitate will

16.  3. Single reactions often happen
as part of a larger series of
reactions.When a plant makes
sugars, there might be as many as a
dozen chemical reactions to get
through the Calvin cycle and
eventually create
(synthesize) glucose(C6H12O6)
molecules. The rusting example we

17. There were several
intermediate reactions where
chemical bonds were created
and destroyed. The silver
chloride example only
focused on the ions. In
reality, the two solutions
were created when two