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NOTES: 2.1 –
The Nature of Matter
Key Questions:
• Identify the three subatomic particles found in atoms.
• Explain how all of the isotopes of an element are
similar and how they are different.
• Explain how compounds are different from their
component elements.
• Describe the two main types of chemical bonds
What makes up all matter?
• A chemical element is a pure
substance that consists of just
one type of atom.
• Atoms are the basic unit of
matter.
• The atom is the smallest unit
which retains all of the physical
and chemical properties of its
element.
Chemical Compound - A substance formed by
the chemical combination of two or more elements
in a fixed proportion.
• The properties of the compound are usually very
different from the elements that make up the
compound.
Examples of Compounds
• Water - H2O
• Salt – NaCl
• Methane – CH4
• Titanium Dioxide – TiO2
Examples of Compounds
Properties of Elements
Three Subatomic Particles
Particle
Proton
Charge
Location
Mass
(+)
Nucleus
1.0007 amu
Neutron
Neutral
Nucleus
1.0008 amu
Electron
(-)
Orbiting
nucleus
0.0005 amu
Atomic Number –
-the number of protons in an atom of an element
•all atoms of an element have the same atomic #
•written as a subscript next to the element’s symbol
•in a neutral atom, the number of protons is equal to the
number of electrons (balanced charges).
Mass Number –
-the number of protons and neutrons in an atom of
an element.
•The number of neutrons may vary, but the proton
number remains constant.
•Written as a subscript next to the element’s symbol
Isotopes-Atoms of an element that have
more or fewer neutrons.
Isotopes•
in nature, elements occur as mixtures of
isotopes.
• some are radioactive: unstable isotope
where nucleus decays emitting sub-atomic
particles and/or energy
Half-Life
the time it takes for half the nuclei in a
radioactive isotope sample to decay
Energy Level of Electrons
Chemical Bonding
Covalent Bond –
strong chemical bond between
atoms formed by electrons
being shared by the atoms.
Ionic Bond –
• bond formed by the attraction of a
positive ion to a negative ion
• Anion – positive ion
• Cation – negative ion
Chemical Reactions
• bonds
between atoms are formed or
broken, causing substances to combine
and recombine as different molecules
CH4 + O2
CO2 + H2O
Chemical Reactions
• All of the chemical reactions that
occur within an organism are
referred to as that organism’s
metabolism
Chemical Reactions
Reactants:
•the substance(s) at the beginning of a
reaction; shown on the left side of the
equation
Products:
•the substance(s) at the end of a reaction;
shown on the right side of the equation.
CH4 + O2
CO2 + H2O