CHEMISTRY of LIFE
Ch 2.1
Composition of Matter

Matter - Everything in
universe is composed of
matter
 Matter is anything
that occupies space or
has mass
 Mass – quantity of
matter an object has
 Weight – pull of
gravity on an object
Questions



Is weight and mass the same thing?
Would I weigh more on the moon or
on Earth?
Is my mass the same on the moon
and on Earth?
Elements


Pure substances that cannot be
broken down chemically into simpler
kinds of matter
More than 100 elements (92
naturally occurring)

Each element
unique chemical
symbol
 Consists of
1-2 letters
 First letter
is always
capitalized

90% of the mass of
an organism is
composed of just 4
elements
 oxygen
 carbon
 hydrogen
 nitrogen
Atoms


An Atom is the
simplest particle of an
element that retains
all the properties of
that element
Properties of atoms
determine the
structure and
properties of the
matter they compose
Do you know?



All matter is made up of atoms
Atoms are the smallest part of a
substance that is still that
substance
Atoms are very, very small
The Nucleus




Central core of the
atom
Consists of positive
charged protons and
neutral neutrons
Positively charged
Contains most of
the mass of the
atom
The Protons



All atoms of a given element have the
same number of protons
Number of protons called the atomic
number
Protons and electrons are equal to
create a neutral element
Practice

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Periodic table on back cover
or page 1086
Atomic number of oxygen (O)
 8
Atomic number of zinc (Zn)
 30
# protons in bromine (Br)
 35
protons in gold (Au)
 79
Element with 44 protons
 Ruthenium (RU)
3/24/2016
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END OF PART 1