Download Atomic Structure and Elements

Atomic Structure
and the Elements
1
What is an atom?
1 AMU
1 AMU
++
1 AMU
1 AMU
An atom is the smallest particle of an element.
Atoms make up all matter.
2
Basic Structure of the Atom
• Nucleus - center of the atom that contains:
– Protons - (p+) - positively charged
– Neutrons - (n) - no charge
• Energy Levels / Orbits - paths that
electrons (e-) travel around the nucleus
– Electrons – (e-) – negative charge
- In a neutral atom:
Number of protons (+)= Number of electrons (-)
Nucleus with
Protons &
Neutrons
+ +o
o
Energy Levels
with Electrons
3
Basic Structure of an Atom
AMU is an atomic mass unit.
1 AMU
1 AMU
+
o
1 AMU
+
o
1 AMU
•Each proton and
neutron has 1 AMU
•Electrons do not have
much mass compared
to protons and
neutrons so we don’t
count any mass for
them
4
Where did the Atomic Theory
come from?
• John Dalton (1766-1844)
– Published detailed theory in 1808
– Elements are composed of atoms
– Atoms of different elements have different
properties
– Atoms are NOT changed by chemical
reactions, just rearranged
– Compounds are defined by the number,
type and proportion of atoms
5
Expanding the Theory
• Thomson (1856-1940)
– Identified the electron (1897)
– Found it had a negative charge
– Positive sphere and negative
electrons embedded
– Atom is neutral-positive cancels
negative
6
Developing the Theory
• Rutherford - discovered that atom has
a nucleus (1911)
• Bohr-discovered electrons orbit
nucleus (1915)
• Schrodinger-discovered electron cloud
(1926)
• Chadwick-discovered neutrons (1932)
7
8
What Do You Notice?
1
H
1.01
3
4
5
6
7
8
2
He
4.0
9
10
Ne
Li
Be
B
C
N
O
F
6.94
9.01
10.81
12.01
14.01
16.00
19.00
11
12
13
14
15
16
17
Na Mg
22.99
24.31
19
20
K
Ca
39.10
40.08
Al
26.98
20.18
18
Si
P
S
Cl
Ar
28.09
30.97
32.07
35.45
39.95
You should notice the
numbers are getting bigger
from left to right and from
top to bottom.
9
Let’s take a closer
look at
all those numbers…
10
Element Name
Atomic Number
(# of protons and # of electrons)
Element Symbol
(1st letter capital & if a second it is
lower case letters)
Atomic Mass
Beryllium
4
Be
9.01
(total # of protons and neutrons)
11
Beryllium
4
Chemical Symbols
Be
9.01
•Abbreviated way to write the name of an element
•One capital letter or one capital letter and one lower
case letter
•Some symbol abbreviations are for the LATIN name
for the element
12
Beryllium
4
Be
9.01
If the atomic number tells me
the # of Protons and # of
Electrons…
How do I figure out the number
of Neutrons?
Use the formula below:
Atomic Mass - Atomic Number = # of Neutrons
P= 4
E= 4
N=
9-4=5
?
13
Beryllium
4
Okay – If this tells me the # of
Protons and the # of Electrons…
Be
How do I figure out the number
of Neutrons?
9.01
Easy – use the formula below:
Atomic Mass - Atomic Number = # of Neutrons
P=4
E=4
9-4=5
N = 5 Neutrons
14
Let’s Practice.
Nitrogen
Fluorine
7
9
17
N
F
Cl
14.01
18.98
Chlorine
35.45
What are the numbers of protons,
electrons and neutrons?
15
What is an Isotope?
A given Element usually has
differing amounts of neutrons.
These different forms are called isotopes.
16
Isotopes - Continued
Let’s take hydrogen as an example:
As you can see from the atomic
mass (1.01) the most naturally
abundant form of hydrogen does
not have a neutron.
However, in rare instances isotopes
form. Below are the isotopes of
hydrogen:
1
Hydrogen
H
1.01



Protium
Deuterium
Tritium
…. are isotopes of hydrogen.
17
Isotope Notation
C
12
6
Mass number superscript – superman flying
Atomic Number subscript - submarine
Mass Number
Atomic Number
Carbon - 12
Mass Number
How many protons, electrons and neutrons?
Protons = 6
Electrons = 6
Neutrons = 12 – 6 = 6
18
Isotope Notation - Continued
Mass Number
Atomic Number
C
14
6
Carbon - 14
How many protons, electrons and neutrons?
Protons =
6
Electrons = 6
Neutrons = 14 – 6 = 8
19
How many protons, electrons and neutrons?
Which example(s) are isotopes?
Example 1:
Example 2:
Example 3:
How many e-?, P?, n?
N
16
7
Magnesium - 24
10 Neutrons
What element?
Write this element as
demonstrated in
Examples 1 & 2.
20
What are Bohr Models?
Neils Bohr devised a method for drawing
models to represent the atoms nucleus and
their electron arrangement because the
atoms are too small to see.
These models are easy to draw – if you
follow the steps!
21
Drawing Bohr Models
Step 1:
Write down the # of protons, electrons
and neutrons for each atom’s element.
Fluorine = F
Fluorine
9
F
18.98
(Atomic Number)
#Protons = 9
(Atomic Number)
#Electrons = 9
# Neutrons = atomic
mass – atomic #
# Neutrons = 19-9=10
22
Drawing Bohr Models - Continued
Step 2:
Draw a nucleus inserting the # of
protons and # of neutrons that are
inside.
Fluorine = F
p= 9
n = 10
# protons = 9
# electrons = 9
# neutrons = 10
23
Drawing Bohr Models - Continued
Step 3:
Draw the # of energy rings around the
nucleus by what row it is in on the
Periodic Table.
# of rings = row number
p= 9
n = 10
Fluorine is in row #2
so, I need to draw 2
rings around the
nucleus.
24
Drawing Bohr Models - Continued
Step 4:
Place the electrons on the correct
energy ring – filling each to capacity.
3
Energy Levels are Identified as:
4
1st Level –holds 2e-
9
2
P= 9
N = 10
1
5
2nd Level –holds 8e-
6
3rd Level –holds 8eRemember we need to have 9
electrons total for fluorine!
8
7
25
Complete Bohr Model
Fluorine = F
3
4
# Protons = 9
# Electrons = 9
# Neutrons = 10
5
2
9
P= 9
N = 10
8
7
6
1
Energy Level
Max # of
Electrons
1
2
2
8
3
8
26
Happy / Stable Elements
Elements that have a full outer ring of electrons
are called “happy” atoms.
Max # of
Energy Level
Meaning that – that ring can’t
hold any more electrons.
So, if the 2nd ring has 7
electrons in its outer ring – it is
still hungry for the 8th electron –
needing it to be “happy.”
Electrons
1
2
2
8
3
8
27
Happy / Stable Elements
The last ring or outer shell of the atom is called the . . .
Valence shell or outer energy
level
Remember the # of rings that you drew in the
Bohr model is equal to the Row number that
the element is in on the Periodic Table.
2
He
4.0
5
6
7
8
9
10
Ne
B
C
N
O
F
10.81
12.01
14.01
16.00
19.00
13
14
15
16
17
Al
26.98
20.18
Fluorine = Row 2
Fluorine energy level= 2
18
Si
P
S
Cl
Ar
28.09
30.97
32.07
35.45
39.95
28
Happy / Stable Elements
The number of electrons in that last ring or
outer energy level are called the . . .
Valence Electrons
Valence electrons are important
because you will use them to make
compounds.
Fluorine = Column VIIA
Fluorine Valence # = 7
2
He
4.0
5
6
7
8
9
10
Ne
B
C
N
O
F
10.81
12.01
14.01
16.00
19.00
13
14
15
16
17
Al
26.98
20.18
18
Si
P
S
Cl
Ar
28.09
30.97
32.07
35.45
39.95
29