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Matter and
Atomic
Structure
Chapter 2
What Are
Elements?
Elements
All matter is made of elements
Element - a substance that
cannot be broken down into
simpler substances by physical
or chemical means
What are some examples?
Gold
How many are there?
92 naturally occuring
Elements
Identified with 1, 2, or 3 letter
symbols
Examples:
Oxygen - O
Sodium - Na
Unununium - Uuu
Elements are
Made of Atoms
Each element has its own
characteristics.
Atom - smallest particle of an
element that has all the
characteristics of that element
Elements are
Made of Atoms
Atoms consist of a nucleus
with:
Protons - (p+); has mass and a
positive electrical charge
0
Neutrons (n ); same mass as a
proton and NO electrical charge
Surrounding atoms are:
(e );
Electrons has little mass
and a negative charge
Atomic Number
Atomic Number - The number
of protons in an atom’s
nucleus
Oxygen has 8 protons, so its
atomic number is 8
Carbon has 6 protons, what’s the
atomic number?
Molybdenum’s atomic number is
42, how many protons?
Atomic Mass
Atomic Mass - protons +
neutrons
Uranium - 92 protons and 146
neutrons
Mass number = 92 + 146 = 238
Silver (Ag) has an atomic mass
of 107 and an atomic number of
47. How many neutrons does it
have?
60