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What are elements?

Element: Substance that
cannot be broken down into
a simpler form by ordinary
chemical means.




All matter is made of
elements
92 naturally occurring
elements on Earth.
Elements are made up of
atoms.
They Might Be Giants
Components of an atom

Atoms: Smallest
particle of an element
that has all
characteristics of an
element.
• Nucleus: Center of
the atom
•
Protons: “Large”,
positively charged
particle.
• Neutrons: “Large”,
neutral particle.
Components of an Atom
 Outside
the nucleus:
 Electrons:
Negative charge found
outside the nucleus in the electron
cloud.
• 1st energy level: Can hold 2 electrons
• 2nd energy level: Can hold 8 electrons
• 3rd energy level: Can hold 18 electrons


Atomic Number: Number of protons in
the nucleus. This determines what
element the atom is!
There are an equal number of protons &
electrons in a neutral atom
 *Nucleus has a positive charge*

*Atoms have neutral charge*
Atomic Mass: Mass of the nucleus
(Number of protons + Number of
neutrons)
 The number of neutrons can vary in an
atom, but the protons will always be
equal to the atomic number.

Isotope Notation
Mass #
Atomic #
15
8
O
Protons
Electrons
Neutrons
8
8
15-8 =
7
How to determine Atomic and
Mass #s


If you are not given the atomic number, simply
look at the periodic table.
If you are not given the mass
number…


If you have protons and neutrons, add them
If you don’t have protons and neutrons, take
the mass from the periodic table and round
to the nearest whole number
Name
Symbol
Sodium
Br
Atomic
number
Mass
Number
# of
Protons
# of
Neutrons
# of
electrons
Name
Symbol
Sodium Na
Br
Atomic
number
Mass
Number
11 22.99
# of
Protons
# of
Neutrons
electrons
11
12
11
# of
Name
Symbol
Sodium Na
Bromine
Br
Atomic
number
Mass
Number
# of
Protons
# of
Neutrons
electrons
11
12
11
35 79.90 35
45
35
11 22.99
# of
Practice
•
How many protons are there in Lithium-7?
•
How many neutrons are there in Lithium-7?
•
How many protons are there in Mg?
•
How many electrons are there in Mg?
•
How many neutrons are there in 9 F ?
•
How many neutrons are there in Oxygen-18?
20
Practice
•
How many protons are there in Lithium-7? 3
•
How many neutrons are there in Lithium-7? 4
•
How many protons are there in Mg? 12
•
How many electrons are there in Mg? 12
20
9
F
•
How many neutrons are there in
? 11
•
How many neutrons are there in Oxygen-18? 10
Isotopes

Atoms of the same element (same #
of protons), but with different
numbers of neutrons.


Have different mass numbers
Isotopes behave the same
chemically because they still have
the same number of protons and
electrons
Isotopes of Neon
20
10
Ne
21
10
Ne
22
10
Ne
Protons
10
10
10
Electrons
10
10
10
Neutrons
10
11
12
Ions

So far, we have focused on neutral
atoms


Which have an equal number of
protons and electrons
We know the protons are tightly
held in the nucleus
 Held
there by nuclear forces
Ions

Electrons are scattered outside the
nucleus
 Less
restricted and able to
change
 When
an atom gains or loses
electrons, it is called an ion
Gain Electrons

Negative charge

Called an anion
Ex.
16
8
O
Protons
Electrons
Neutrons
2
Gain Electrons

Negative charge

Called an anion
Ex.
16
8
O
Protons
Electrons
Neutrons
2
8
10
8
Lose Electrons

Positive charge

Called a cation
Ex.
27
13
Al
Protons
Electrons
Neutrons
3
Lose Electrons

Positive charge

Called a cation
Ex.
27
13
Al
Protons
Electrons
Neutrons
3
13
10
14
Particle Changed
Result
Proton
Different Element
Neutron
Isotope (of same
Electron
element)
Ion
(of same element)
Normal: Atomic Mass _______
Chlorine has
________ # of protons
_________ # of Neutrons
_________ # of Electrons
Isotope: Atomic Mass 37
ISOTOPE)
Electrons
________ # of protons
_________ # of Neutrons
_________ # of
Normal: Atomic Mass _35.45__
Chlorine has
__17____ # of protons
____18___ # of Neutrons
___17____ # of Electrons
___20____ # of Neutrons
____17___ # of Electrons
Isotope: Atomic Mass 37
___17___ # of protons
Atom Bonding


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Valence electrons:
Electrons found in the
outermost energy level.
Atoms bond with each
other according to the
number of valence
electrons in order to be
stable.
Stable atom=Outermost
electron valence shell is
full.
Chemical Bonds

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Ionic Bonds
Covalent Bonds
Hydrogen Bonds
Ionic Bonds

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
Electrons are transferred between atoms
A metal and a nonmetal
Positive & Negative Ions attract each
other like magnets.

In a chemical formula, the positive ion is
always written before the negative ion
 Ex:
Na+ Cl-
Covalent Bonds
Electrons are shared between atoms
 Both are nonmetals

• Polar molecule- shares the electrons uneqaully,
giving it a + and – side.

Nonpolar molecules share equally.
Hydrogen Bonds
Weak, intermolecular bonds
 Formed when the + side of one
polar molecule is attracted to the –
side of another polar molecule.
