Atomic structure

1
ATOMIC STRUCTURE
2
HISTORY OF THE ATOM
Democritus develops the idea of atoms
460 BC
He pounded up materials in his pestle and mortar
until he had reduced them to smaller and smaller
particles which he called
ATOMOS (greek for indivisible)
3
HISTORY OF THE ATOM
SCIENTIST MODEL OF THE ATOM MAJOR CONTRIBUTIONS POINTS
 DALTON (1803)       AKA Billard Ball model Matter is made of small particles called atoms. 1. Atoms are indestructible. They cannot be created or destroyed during chemical or physical changes. Atoms of an element are identical. They have the same mass. Atoms of different elements have different masses. Compounds are formed by combining atoms of different elements.
4
8 X2Y
Law of Conservation of Mass
2.1
5
HISTORY OF THE ATOM
SCIENTIST MODEL OF THE ATOM MAJOR CONTRIBUTIONS POINTS
 THOMPSON (1890s)      AKA plum pudding model   discovers electrons (negative charge)   electrons scattered unevenly within an elastic sphere surrounded by a soup of positive charge to balance the electrons charge
electrons
6
HISTORY OF THE ATOM
SCIENTIST MODEL OF THE ATOM MAJOR CONTRIBUTIONS POINTS
RUTHERFORD (1909)       Gold foil experiment alpha () particles were fired at Au foil Results KNOWTHIS!!! 99 alpha particles went straight thru, 1 were deflected. Findings 1. Atom has a small, positively charged center. 2. Atom is mostly empty space with negatively charged electrons revolving around the outside
FYI ONLY.If the atom is the Ralph Wilson
Stadium Then the nucleus is a marble on the 50
yard line
(1909 Nobel Prize in Chemistry)
7
http//www.mhhe.com/physsci/chemistry/essentialche
mistry/flash/ruther14.swf
Results 99 of the alpha particles went
straight thru, 1 were deflected.
Be able to explain and summarize Rutherfords
Gold Foil Experiment
2.2
8
HISTORY OF THE ATOM
SCIENTIST MODEL OF THE ATOM MAJOR CONTRIBUTIONS POINTS
 BOHR (1913)       AKA Planetary model electrons move in definite, fixed orbits around the nucleus each orbit only able to contain a set number of electrons.
9
Bohrs Atom- electrons move in definite, fixed
orbits around the
nucleus
electrons in orbits
nucleus
10
HISTORY OF THE ATOM
SCIENTIST MODEL OF THE ATOM MAJOR CONTRIBUTIONS POINTS
QUANTUM MODEL (1930s)       AKA Wave Mechanical or Electron cloud model Electrons have a distinct amount of energy and have wave-like properties. They travel in regions called orbitals. These regions are the most likely location of an electron.
11
HISTORY OF THE ATOM reviewed

• Atomos song http//www.youtube.com/watch?vWK7wuTw
  AiBU

Crash Course https//www.youtube.com/watch?vthnDx
FdkzZs Science Classroom https//www.youtube.com/
watch?vIO9WS_HNmyg
12
Atoms

• The basic unit of Matter
• The smallest particle of an element that retains
  the properties of that element.
• Made up of subatomic particles

13
ATOMIC STRUCTURE All About Atoms
Particle
Charge
Mass
Proton
charge
1amu
Neutron
No charge
1 amu
electron
- charge
1/1836
14
ATOMIC STRUCTURE
He
2
Atomic number
Represents the number of protons in an atom Never
changes P equal to the number of e-
4
Mass Number
the number of protons and neutrons in an
atom Neutrons equal mass - atomic
number of electrons number of protons
15
HELIUM ATOM
Shell
proton
N

-

N
-
neutron
electron
What do these particles consist of?
16
Isotopes

• Atoms with the same atomic number but different
  mass number or
• Atoms having the same number of protons but
  different numbers of neutrons
• Which atom is an isotope of oxygen?
• 1). O 2). O 3). O
• Isotopic notation
• O or O-16

17
16
16
6
8
7
16
17
2.3
18
CHEM DODo You Understand Isotopes? 1.
Define an isotope
6 protons, 8 (14 - 6) neutrons, 6 electrons
6 protons, 5 (11 - 6) neutrons, 6 electrons
Isotope Maker
2.3
19
Atomic number (Z) number of protons in nucleus
Mass number (A) number of protons number of
neutrons
atomic number (Z) number of neutrons OF
NEUTRONS mass number atomic number
2.3
20
Average Atomic Mass

• Average Atomic Mass of an element is the weighted
  average of an elements naturally occurring
  isotopes.
• What is the average mass of cesium given the
  percent abundance of selected cesium isotopes?
• 75 Cs-133 20 Cs -132 5 Cs- 134

21
Practice

• Guide pages 3 and 4
• show work set up and solve

22
Bohr Model of the Atom (planetary model)

• Energy Levels
• Electrons revolve around the nucleus in one of
  several orbits/shells/ principal energy levels
• Principal energy level (PEL) is the same as the
  period number on the periodic table
• There are 7 PELs therefore 7 periods
• PEL is designated by a quantum number (n)

23
2.4
24
Location of electron
According to the Bohr model, electrons are found
in shells around the nucleus

• first shell maximum of 2
  electrons
• second shell maximum of 8 electrons
• third shell max of 18
  electrons
• fourth shell max of 32 electrons

25
ATOMIC STRUCTURE
There are two ways to represent the atomic
structure of an element or compound
1. Electronic Configuration
2. Electron dot diagrams
26
ELECTRONIC CONFIGURATION
With electronic configuration elements are
represented numerically by the number of
electrons in their shells and number of shells.
For example
Nitrogen
configuration 2 , 5
14
2 in 1st shell 5 in 2nd shell
N
7
2 5 7
27
ELECTRONIC CONFIGURATION
Write the electronic configuration for the
following elements
20
11
8
O
Na
Ca
a)
b)
c)
16
23
40
2,8,8,2
2,8,1
2,6
14
Si
17
5
Cl
B
d)
e)
f)
11
35
28
2,8,7
2,8,4
2,3
28
Valence

• Valence shell is outermost occupied energy level
  and is the same as the period number in the
  periodic table
• Valence electrons are the electrons in the outer
  energy level of an atom

29
DOT CROSS DIAGRAMS
With Dot Cross diagrams elements and compounds
are represented by Dots or Crosses to show
electrons, and circles to show the shells. For
example
X
14
Nitrogen
N
X
X
X
X
N
X
X
7
30
DOT CROSS DIAGRAMS
Draw the Dot Cross diagrams for the following
elements
X
35
16
X
Cl
O
a)
b)
X
X
17
8
X
X
X
X
X
Cl
X
X
X
X
X
X
O
X
X
X
X
X
X
X
X
X
X
X
31
An ion is an atom, or group of atoms, that has a
net positive or negative charge.
cation ion with a positive charge If a neutral
atom loses one or more electrons it becomes a
cation.
anion ion with a negative charge If a neutral
atom gains one or more electrons it becomes an
anion.
2.5
32
Do You Understand Ions?
13 protons, 10 (13 3) electrons
34 protons, 36 (34 2) electrons
2.5
33
A monatomic ion contains only one atom
Na, Cl-, Ca2, O2-, Al3, N3-
A polyatomic ion contains more than one atom
OH-, CN-, NH4, NO3-
2.5
34
SUMMARY

• The Atomic Number of an atom number of
• protons in the nucleus.
• The Atomic Mass of an atom number of
• Protons Neutrons in the nucleus.
• The number of Protons Number of Electrons.
• Electrons orbit the nucleus in shells.
• Each shell can only carry a set number of
  electrons.