Chemistry:
THE STUDY OF MATTER

So what is matter?
Matter
 Must
 It
have mass
is different from weight…..Why?
 Must
occupy space (have volume)
Matter Has Density

Density of a Substance
=
Mass
Volume
See Reference Table S to compare density of elements
States of Matter

Matter can exist in three basic states:


Solid (s), Liquid (l), Gas (g)
How are these states different from each other?
Can Matter be Destroyed?
Example:

When 400 grams of wood
are burned only about 30
grams of ash remain.

What would you think?

What happened to the
missing matter?
Law of Conservation of Matter

Matter cannot be
created or destroyed
Matter isn’t being lost
but changing in form!

Atoms are all still
there they just get
rearranged

Balanced chemical equations show the
number of atoms stay the same during
reactions and thus obey this law.
Basic Types of Matter:
Elements vs. Compounds
Elements
•
Made of atoms of one specific type
•
Cannot be broken down chemically
•
Have specific properties.
Examples of Elements
Where Do We Get Elements?

Obtained in
nature in their
pure state.

Found combined
with other elements
in compounds

Man-made through
nuclear bombardment
reactions
Elements and Their Symbols

Take Note Please!

Elements have either one
or two letters when they
are written as a symbol.

If two letters, the second
letter is written lower
case. (Ex: Write Cu for
copper not CU)

Why is this so important?

Usually it is pretty easy to match an
element to its symbol (Ex: Neon = Ne)

Sometimes the symbol is derived from a
Latin name for the element.

Ex: Au = gold (comes from Latin word aurum)
Tricky Elements











Na = sodium
K = potassium
Fe = iron
Cu = copper
Sb = antimony
Sn = tin
Pb = lead
Hg = mercury
W = tungstun
Au = gold
Ag = silver
Phases and Elements

Solids:

Most elements are solids

Gases:
 H, He, Ne, Ar, Kr, Xe, Rn,
N, O, F, Cl

Liquids:
 Hg, Br

Let’s make a note of these on our
Periodic Tables!
Diatomic Elements

Most elements are
monoatomic in pure form.

Some elements have two
atoms joined (diatomic)
Who are they?
 Remember BrINClHOF

Let’s make a note of these on
our Periodic Tables!
Compounds

Two or more different elements bonded
together chemically
Ex: C6H12O6, NO2, CO2, NaCl

Note: Most elements in nature do not exist in
their pure state, but in compounds.

Why?
Law of Definite Proportions
•
Compounds have specific
formulas that show the
proportion of elements to
each other.
•
•
Ex: Water is always H2O
A “mixture” has proportions
that can vary
•
Ex: salt water
Getting New Properties

Compounds have different chemical and
physical properties than the elements that
make them up.
- Sodium (Na)
Toxic metal
- Chlorine (Cl)
Toxic gas
Sodium Chloride (NaCl)
White edible crystal
salt for my french fries!!
Focus Question
 What
makes atoms of one element
different from another?
 What
is inside its atoms…
Atomic Basics

Atoms consist of three basic parts.
Protons
 Neutrons
 Electrons


Fill in Chart:
Particle
Proton
Neutron
Electron
Charge
Mass
Location
Symbol

Atomic Number:
Tells us the number of
protons in nucleus
 It is unique for each
element

Does an Atom Have a Charge?

Atoms are neutral particles

Number of electrons (-) = number of protons (+)

How many electrons does an atom of carbon
have?
Does the Nucleus have a Charge?

Nuclear Charge:
 the
charge on the nucleus of the atom.
 (+) positive charge = to number of protons
What is the Nuclear Charge?
What is the Atomic Number?
What is this Element?
Atoms vs. Ions

Ions: atoms with a charge
Protons don’t equal electrons!!
 Atom has gained or lost electrons

 Gain
electrons: become (-) ion
 Lose electrons: become (+) ion
P=9
E = 10
What is the element? What is it’s ionic charge?
Ionic Charge Practice
Try a few for practice…
Atomic Mass Number

Atomic Mass Number:
Sum of the number of protons + neutrons
 Each has a mass of 1 amu. (atomic mass unit)

Ex:
P = 23
N = 21
What is the Atomic Mass Number?
What is this element?
Isotopes

Isotopes: atoms of the same element with
different atomic mass.
Same # protons
 Different # neutrons


Ex: Carbon-12, Carbon-14 (two isotopes of C)
 How
many protons?
 How many neutrons?
Average Atomic Mass

Average Atomic Mass:

The atomic mass you see on the periodic
table

Based upon abundance of isotope and its
mass in an sample of the element

Calculating Average Atomic Mass

Mass of each isotope x abundance
(change % abundance to decimal)

Add together answers

Ex: Chlorine