#### Transcript Chapter 2 Chemistry of Life

```Chapter 2 Chemistry of Life
SECTION 1 COMPOSITION OF
MATTER
PG. 31
 Matter- anything that occupies space and has mass
Is air matter?
Does it occupy space?
Does it have mass?
 Mass- the quantity of matter an object has; mass doesn’t
change
 Weight- the force of gravity acting
on mass
Elements and Atoms
 Elements- substances that cannot be broken down
chemically into simpler kinds of matter
> 100 have been identified
• 90% of living things are
composed of just 4 elements:
oxygen, carbon,
hydrogen, and nitrogen
The Periodic Table
 A chart showing information about the elements
(the back cover of most of your books)
Dmitri Mendeleev
6
Atomic number
C
Element symbol
Carbon
12.0107
=
# of protons
Element name
Atomic mass (Round this to get
mass number)
How can you determine the number of electrons?
How do you find the number of each type of particle?
(protons, neutrons, and electrons)
 The number of protons is the ATOMIC NUMBER
 Elements are arranged on the Periodic Table by their
atomic number
 The number of electrons is the same as the number
of protons
 The MASS NUMBER is the atomic mass rounded.
 The number of neutrons is calculated
by subtracting the atomic number from
the mass number.
Many symbols of elements are based on their
Latin names
Sodium
Na
Natrium
Pb
Plumbum
What is an atom?
 Atom-the simplest particle of an element that retains
all of the properties of that element
The world’s largest gold bar:
551 lbs
The price of gold is over
\$900.00/oz
551 lbs x 16 oz/lb = 8,816 oz
= \$\$\$\$\$
The Structure of the Atom
 There are many models used to represent the
structure of an atom.
 One of those is the Bohr model:
It shows the nucleus or the center
of the atom where the protons and
neutrons are located.
It also shows the arrangement of
electrons in energy levels around
the nucleus.
3 particles of an atom
Protons- in the nucleus; positive charge
Electrons- in energy levels around the
nucleus ; negative charge
Neutrons- in the nucleus; neutral charge
The mass number is the number of protons +
the number of neutrons
Other atom models:
Notice the protons and neutrons in the nucleus…
and the electrons spinning around the nucleus…
Energy Levels of Atoms
Energy levels are also called orbitals.
Each energy level can hold only a certain # of electrons…
1st energy level holds 2e2nd energy level holds 8e3rd energy level holds 8e4th energy level holds 16eWhat element is shown above?
Isotopes
Atoms of the same element that have
different numbers of neutrons.
*Red= proton
Hydrogen
Protons
Electrons
Neutrons
1
1
0
Gray=neutron
Deuterium
1
1
1
Tritium
1
1
2
Compounds
Compound- substances made up of two or more elements in
fixed proportions.
Represented by a chemical formula.
For example, water: H2O
and
glucose: C6H12O6
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