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1
Atoms pp.32-37
The Rutherford model of the atom (1911)
2
Atoms Matter – Anything that has mass,
takes up space (volume) and has some sort of atomic structure.
3
Atoms Atoms – are the smallest, simplest
fundamental units of matter.– The building blocks of matter.
Atoms are composed of 3 subatomic particles:– Protons, Neutrons, Electrons
4
Atoms
Elements – are matter that is composed (made up of) only one type of atom.– A pure substance (like Au, Ag, Pt, Cu or
Al)– Your bling is NOT an element
Insert periodic table here
Periodic Table of the Elements
6
PERIODIC TABLE P. 712 The periodic table is an organized listing
of all known types of elements.
H
Hydrogen
1
1.008
Name of element
Chemical symbol
Atomic Mass (weight)
AtomicNumber
7
PERIODIC TABLE P. 712The first 92 elements are naturally occurring, meaning they are found on earth and are NOT man made. All the rest are made in a lab or nuclear reactor.
Ca
Calcium
20
40.078
Name of element
Chemical symbol
Atomic Mass (weight)
AtomicNumber
8
Atomic Mass (Mass Number)
The atomic mass of an atom is equal to the sum of its protons and neutrons.– Atomic mass is also known as mass number or
atomic weight.
Mass is expressed in units called AMU’s (Atomic Mass Units)
9
Atomic Number
The atomic number is equal to the number of protons in the atom’s nucleus.
– Remember the number of protons tells you which atom/element you have.
10
ATOMIC mass minus the ATOMIC NUMBER equals the number of NEUTRONS in the nucleus
Atomic Mass - Atomic # = # NEUTRONS
HHydrogen
1 1.0079
What does the nucleus ofhydrogen have in it ?
11
12
Periodic Table - Atomic Symbols
Information on an element is noted in different ways in different texts and periodic tables.
C
12
6
Mass Number
Atomic Number
6
C12.01
Atomic Number
Average atomic mass
13
3 4 5 6 7
8
Transition Metals = almost all have 2 valence e-
PERIODIC TABLE P. 712
14
Periodic Table P. 712
15
Periodic Table P. 712
Los Alamos National Lab Interactive Periodic Table
16
Model of an atom
Atoms are too small to see even with a microscope. So we use models!– A cubic centimeter of air has 45 billion billion
atoms in it. That’s 45 with 18 zeros after it.– Another Example: Take a millimeter, divide into
1000 equal widths (called microns).– Now take one of those microns and divide it into
10,000 equal pieces. (one ten-millionth of a millimeter).
– That is how small an atom is!!!!!!
The Modern Model of the Atom
(Schroedinger 1926)
Dalton’s Model of the Atom (1803)
Rutherford Atomic Model (1911)
The Model of the Atom
(1904)Bohr Model of the Atom (1913)
Parts of the atom P. 35
ElectronsProtons
Neutrons
19
Model of an atom
Atoms are mostly EMPTY space.
10-15 m
Neutron
Proton
Nucleus (protons and neutrons)
Space occupied by electrons
10-10 m
Model of an atom• Protons and neutrons are found INSIDE the
nucleus, and electrons are found as a cloud outside the nucleus.
10-15 m
Neutron
Proton
Nucleus (protons and neutrons)
Space occupied by electrons
10-10 m
21
PROTONS
PROTONS – are subatomic particles found in the nucleus of the atom.
have a mass of 1.0 Atomic Mass Unit – let’s just call it 1.0 amu.
have a positive electrical charge of +1.
The number of protons determines the atom’s identity.
The nucleus is positively charged.
P
22
NEUTRONS
NEUTRONS – are subatomic particles found inside the nucleus.
have a mass of slightly more than 1.0 amu.
Have an electrical charge of zero – thus they are neutral (hence the name).
The atomic mass of an atom is the number of protons + neutrons inside its nucleus.
If an atom has more or less neutrons than it normally should have, we call it an ISOTOPE.– Carbon-14 is an isotope of carbon, is radioactive and is used to date
fossils (like Mr, Mauer). More later.
N
23
ELECTRONS
Subatomic particles found in electron shells or orbitals OUTSIDE the nucleus.
An electrons Mass is very tiny - let’s just call it zero (0).
Electrical charge is -1 (exactly opposite of the protons).
e
24
ELECTRONS
Electrons determine the chemical properties of an atom. (how it reacts/behaves around other atoms).
Have potential energy.
The farther away from nucleus, the more energy they have.
Can change energy levels/shells/orbitals
25
ELECTRONS
Atoms normally have a zero net charge overall.
That means the number of protons(+) in an atom equals the number of electrons(-).
Sometimes atoms may lose or gain electrons and become electrically charged atoms called IONS.
Subatomic Particles(parts of the atom)
Charge Mass Location
Proton (p+) +1 1.0073 amu
(about 1 amu)
nucleus
Neutron (n0) 0 1.0087 amu
(about 1 amu)
nucleus
Electron (e-) -1 0.00055 amu
(essentially 0 amu)
Outside nucleus
1 amu (atomic mass unit) is defined as 1/12 the mass of the carbon atom with 6 protons and 6 neutrons.
1 amu = 1.7 X 10-24 g (0.0000000000000000000000017 g)
27
ISOTOPES
ISOTOPES are atoms of the same element which have different atomic weights because they have different numbers of neutrons.
For instance– Carbon normally has 6 protons, atomic mass of
12. (C-12)– Carbon can also have atomic mass of 13 (C-
13).– Carbon also exists with atomic mass of 14 (C-
14). Differences due to number of neutrons, not
protons
28
Understanding Atoms
This diagram shows how to draw electrons for each energy level of an atom. A scientist named Neils Bohr created this representation.
1st energy level
2nd energy level
3rd energy level
4th energy level
Max. 2
Max. 8
Max. 18
Max. 32
•Atomic Mass•Atomic Number•All atoms are usually neutrally charged
30
ELECTRON Energy Levels (Shells/Orbitals)
The first electron shell is full with 2 ELECTRONS
The second shell is full with 8 ELECTRONS
The third shell is full with 18 ELECTRONS.
The fourth shell is full with 32 ELECTRONS.
Electrons in the outermost shell are called VALENCE ELECTRONS.– These electrons are reactive and are involved in bonding to other
atoms (when the shell is not full!)
2, 8 , 18, 32, 32, 18, 8
31
32
33
ON THE TEST????
Be prepared to answer questions about the first 20 elements
Examples: atomic number, atomic mass, electron configurations, valance electrons, etc.
34
WHY LEARN JUST THE FIRST 20?
Living things are composed of simple, common atoms...
NOT the big, rare fancy atoms ....
In fact about 95 percent of your body is composed of just 6 common atoms ....
CHNOPS - Remember these!
CARBON, HYDROGEN, NITROGEN, OXYGEN, PHOSPHORUS AND SULFUR
35
WHAT DOES HYDROGEN LOOK LIKE ?
EPe-
+
Atomic Number = 1Atomic Mass Number = 1Electrical Charge = neutral
36
HELIUM
HeHelium
2 4.0026
Can you draw this Bohr Model ?
37
THE BOHR MODEL FOR HELIUM
PN
N
P
e-
e-
++
0
0
Atomic Number = 2Atomic Mass Number = 4Electrical Charge = neutral
38
LITHIUM
LiLithium
3 6.941
39
THE LITHIUM MODEL
N43
THE FIRST SHELL IS FULL WITH TWO ELECTRONS
eP
e -
-
e-
+0
Atomic Number = 3Atomic Mass Number = 7Electrical Charge = neutral
40
CARBON
CCarbon
6 12.011
41
THE CARBON MODEL
N66 P
e-e-
e-
e-
e- e-+
0
Atomic Number = 6Atomic Mass Number = 12Electrical Charge = neutral
42
SODIUM
NaSodium
11 22.989
43
THE SODIUM MODEL
N1211
2
8
1 E
E
EP
Atomic Number = 11Atomic Mass Number = 23Electrical Charge = neutral
44
POTASSIUM
KPotassium
19 39.102
45
THE POTASSIUM MODEL
N2019
2
8
9E
E EP
Atomic Number = 19Atomic Mass Number = 39Electrical Charge = neutral