Section 42 Objectives State the three subparticles of atoms State the charges of the subparticles Describe the composition of an atom Atom Fundamental particles which make up matter The smallest particle of an element that retains keeps its identity in a chemical reaction ID: 316323
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Slide1
Atoms
Section 4.2Slide2
Objectives
State the three
subparticles
of atoms
State the charges of the
subparticles
Describe the composition of an atomSlide3
Atom
Fundamental particles which make up matter
The smallest particle of an element that retains (keeps) its identity in a chemical reactionSlide4
Atomic Structure OverviewSlide5
Early Models of the AtomSlide6
Democritus’s
Atomic
Philosophy
460 B.C. to 370 B.C.
First suggested the existence of atoms
400 B.C.
Believed atoms were:
Indivisible
Indestructible
Theory faults
Did not explain chemical behavior
Lacked experimental support
not based on the scientific methodSlide7
Dalton’s Atomic
Theory
2000 years after Democritus
John Dalton (1766-1844)
By using experimental methods, he transformed Dem. ideas on atoms into a scientific theory.
Studied the ratios in which elements combine in chemical
rxnsSlide8
Dalton’s Atomic Theory
All elements are composed of tiny indivisibly particles called atoms.
Atoms of the same element are identical. The atoms of any one element are different from
tose
of any other element.
Atoms of different elements can physically mix together or can chemically combine in simple whole-number ratios to form compounds.
Chemical reactions occur when atoms are separated, joined, or rearranged. Atoms of one element, however are never changed into atoms of another element as a result of a chemical reactionSlide9
Dalton’s Atomic
TheorySlide10
Example of a TimelineSlide11
Sizing Up the
Atom
Atoms are VERY small
100,000,000 copper atoms side by side = 1 cm
Radii of an atom
5 x 10
-11
m to 2 x 10
-10
m
Individual atoms can be seen with instruments like a scanning tunneling microscope
Have the ability to move around and arrange them in patternsSlide12
Scanning Tunneling MicroscopeSlide13
Quarks: The smallest particlesSlide14
QuarksSlide15
Atoms
Composed of:
Electrons
Negatively charged particles
Nucleus
Located in the center of the atom
Positively charged
Contains all of the mass of the atom
Contains protons
Particles with a charge of +1
Neutrons
Particles with no chargeSlide16
Particle
Symbol
Location
Charge
Electron
e-
In the space surrounding the nucleus
1-
Proton
p+
In the nucleus
1+
Neutron
n
O
In the nucleus
0
Properties of Subatomic ParticlesSlide17
Electrons
Fast moving
Travel through the space around the nucleus
Held within the atom because of the attraction to the positive nucleusSlide18
How Atoms DifferSlide19
Objectives
Explain the role of the atomic number in determining the identity of an atom
Define an isotope and explain why atomic masses are not whole numbers
Calculate the number of electrons protons and neutrons in an atom given its mass number and atomic number.Slide20
Atomic Number
Atoms of an element have a unique positive charge in their nuclei
Number of protons determines the properties of an element
Atomic number
= # of protons = # of
electons
Determines the elements position on the periodic tableSlide21
Isotopes
Atoms with the same number of protons but different number of neutrons
Differ in mass
More neutrons = more mass
Same chemical behavior
Chemical behavior is determined by the # of electrons
Have a number after the element to distinguish one from another
Ex. Potassium-39
vs
potassium-40Slide22
Mass Number
Sum of the protons and neutrons
Number of neutrons = mass # - atomic numberSlide23
Atomic MassSlide24
Mass Spectrometer
Instrument used to find the actual masses of individual atoms
Example:
Fluorine atom
3.155 x 10
-23
g
Small and impractical to work with
NASA-The Molecule Dissector-Mass SpectrometerSlide25
Atomic Mass
Compare the masses of an atoms to an isotope as a standard
Carbon-12
6 protons/6 neutrons
Assigned a mass of 12 atomic mass units
Atomic Mass Unit (
amu
)
1
amu
1/12 of the mass of a carbon-12 atom
The mass of one proton or one neutronSlide26
Element
Number of Protons
Number of Neutrons
Predicted Atomic Mass
Actual Atomic Mass
Helium
2
2
Nitrogen
7
7
Sulfur
16
16
PracticeSlide27
Why not use whole numbers?
Most elements occur as a mixture of two or more isotopes
Each isotope has a different abundance
Atomic Mass of an Element
A weighted average mass of the atoms in a naturally occurring sample of the element
Takes into account:
Mass of isotope
Relative abundance in natureSlide28
Calculating Atomic Mass
Multiply the mass of each isotope by it’s natural abundance (expressed as a decimal)
Add the productsSlide29
Example
Element X has two natural isotopes. The isotope with a mass of 10.012
amu
(
10
X) has a relative abundance of 19.91%. The isotope with a mass of 11.009
amu
(
11
X) has a relative abundance of 80.09%. Calculate the atomic mass of this element.Slide30
Practice
The element copper has naturally occurring isotopes with mass numbers of 63 and 65. The relative abundance and atomic masses are 69.2% for the mass of 62.93
amu
and 30.8% for the mass of 64.93
amu
. Calculate the average atomic mass of copper.Slide31
Practice
Calculate the atomic mass of bromine. The two isotopes of bromine have atomic masses and relative abundance of 78.92
amu
(50.69%) and 80.92
amu
(49.31%. Slide32
The Periodic Table
A PreviewSlide33
The Periodic Table
An arrangement of elements
separated into groups based on similar properties
Allows you to compare one element to the next
Arranged in order of increasing atomic number
Period:
Horizontal row
Group or Family
Vertical columnSlide34
“Name that Element”Slide35
Practice Makes Perfect
Take a minute to look over the names and abbreviations of the elements on the periodic table.
Create 6 flashcards
On one side put the elements name
On the other side put the element’s symbolSlide36
Pick from the following elements for you flashcards:
Hydrogen Sulfur
Lithium Nitrogen
Sodium Carbon
Potassium Gold
Rubidium Silver
Barium Copper
Magnesium
Calcium Iron
Tin
Nickle
Helium
Cobolt
Neon
Argon
KryptonFlorineChlorineBromineIodine
OxygenSlide37
Homework/Class work
Create a concept map on the back of the element symbols WS using the following terms:
Atom
Isotope
Neutron
Atomic mass
Nucleus
Mass number
Atomic number
Proton
Electron