Upload
kellie-mclaughlin
View
221
Download
0
Tags:
Embed Size (px)
Citation preview
The Structure of the Atom and the Periodic Table
Chapters 4 and 5
Atomic Theories- Ancient •Ancient times identify 4 elements:
•Fire
•Water
•Wind
•Earth
•They thought that these elements could be converted into each other through a cycle
end
Atomic Theories- Ancient
Democritus
•1st to propose that there is a smallest particle
•Matter was made up of atomos
•Atoms cannot be created, destroyed, or divided
Aristotle
•Opposed Democritus’ view
•Did not agree with the concept of empty space
•Destroyed Democritus’ theory
end
Atomic Theories- Modern
John Dalton
•English Quaker Schoolteacher
•Father of modern atomic theory
•Spent a great deal of time studying the behavior of gasesHe noticed that in every sample the ratio of the elements was always the same
end
Atomic Theories- Modern
Dalton's Atomic Theory: All elements are made of atoms Atoms of the same element have the same mass
This was later proved wrong- Isotopes Atoms of different elements have different masses Atoms combine in whole number ratios
You can't have half of an atom in a compound
Dalton's Atoms
•Dalton went back to Democritus' view. •All matter is made up of individual particles called atoms, which cannot be divided
•Atoms are little spheres•Like marblesend
Atomic Theories- Modern
Atom The smallest particle of an element that
retains the properties of the element
end
Atomic Theories- ModernJ. J. Thomson
•Performed cathode ray tube experiments
•Discovered the electron
•Proved that atoms can be broken up
•Dalton was wrong
•Created the Plum Pudding Model
When electricity moves through a gas it produces a glowing beam (neon signs)
When a magnetic field was applied the beam went toward the positive plate
end
Atomic Theories- Modern
Thomson had to come up with a new model to explain the electrons
•The Plum Pudding Model
•Large area of positive charge
•Small packets of negative charge
•Think: Chocolate Chip Cookies
end
Atomic Theories- ModernErnest Rutherford
•Conducted the Gold Foil Experiment
•Shot particles at thin pieces of gold foil
•Expected to see particles pass straight through
•Some particles bounced almost straight back
end
Atomic Theories- Modern
His experiment showed that the Plum Pudding Model was wrong
Rutherford came up with a new model of an atom A small, dense, positive nucleus Electrons are outside the nucleus Atoms are mostly empty space
+
Nucleus
Electrons are somewhere in this area
end
Structure of the Atom
Protons, electrons, and neutrons are subatomic particles They make-up an atom
You must be able to identify them by mass, charge, and location
end
Structure of the Atom
The Nucleus
Small dense region in the center of an atom Contains all of an atom’s positive charge And almost all of its mass. Contains protons and neutrons
end
Structure of the Atom
Proton (p+) Found inside the nucleus Charge of +1 Same mass as a neutron If you change the # of protons you get a different
element
end
Structure of the Atom
Electron (e-) Charge of -1 Found outside the nucleus Almost no mass compared to the proton If you change the # of electrons you get a ion
end
Structure of the Atom
•Neutron (n0)
•No charge
•Same mass as a proton
•Found in the nucleus with the proton
•If you change the # of neutrons you get different isotopes
end
Review
Particle Symbol Location Relative Mass
Relative Electrical Charge
Change in Number
Electron e- Outside the
Nucleus
1/1840Basically = 0
-1 Ions
Proton p+ Nucleus 1 +1 Elements
Neutron n0 Nucleus 1 0 Isotopes
end
Isotopes
Isotopes Atoms of the same element Have different numbers of neutrons
Which means different mass numbers
All elements have isotopes In nature the elements occur as a mixture of
isotopes
end
Structure of the Atom
Mass Number The relative mass of each atom The number of protons + the number of neutrons Different isotopes have different mass numbers
Changes the # of neutrons!
Mass# = (Atomic#) + (# of neutrons)
end
Structure of the Atom
Atomic Number The number of protons in the element This defines each element Equals the number of electrons in a neutral atom
Atomic Number
end
Structure of the Atom
• Atomic Symbols– 1 or 2 letters– The 1st letter is always capitalized the 2nd is
always lowercase• Make sure to write your letters correctly!!!!!
– The element’s name is just below the symbol
Atomic Symbol
Element’s Name
end
Structure of the Atom
• Atomic Mass– Weighted average mass for all isotopes of each
element– NOT the same as the Mass Number
Atomic Mass
end
Structure of the Atom
• Writing Atomic Symbols– Since every element has isotopes scientists have
write symbols so the know which one they are talking about
– There are 3 ways to write the symbols:
Carbon- 12 C- 12
Name and Mass Number
Symbol and Mass Number
C126
Symbol
Mass Number
Atomic Number
end
Structure of the Atom
Name Symbol Protons Neutrons Electrons Atomic Number
Mass Number
Carbon-12
136C
15 45
44 34
36 15
end
Atomic Theories- Modern
Rutherford's model was good, but it didn't talk about the electrons
Bohr Model (Solar System Model) Took Rutherford's model and put electrons into
energy levels Electrons change energy levels when they either
gain or lose energy• Electrons cannot be between levels
Electrons can move more than 1 level at a time
end
Atomic Theories- Modern
• In the Bohr Model:– Protons and Neutrons form a nucleus– Electrons are placed in rings around the
nucleus• Each energy level can only hold a certain
number of electrons
Energy Level # of electrons1 2
2 8
3 18
4 32
end
Atomic Theories- Modern
Lets draw H-1
p = 1
n = 0
e = 1
Lets draw He-4
p = 2
n = 2
e = 2
Lets draw Li-6
p = 3
n = 3
e = 3
Lets draw Na-22
p = 11
n = 11
e = 11
end
Atomic Theories- Modern
Electrons want to be in the lowest energy level possible
Ground state All electrons are in the lowest possible energy levels The most stable
Excited state At least 1 electron is not in the lowest possible
energy level
end
Atomic Theories- Modern
Bohr's model was good, but it had problems We can never be sure of exactly where
electrons are located Electron Cloud Model
With some fancy math, we figured out an area around the nucleus where the electrons are going to be 95% of the time This area is known as an Orbital Each orbital can only hold 2 electrons
end
The Periodic Table
By 1860 scientists had discovered 63 elements But there was no good way to organize them Scientists just had to memorized everything about
every element This changed when Mendeleev created a
way to classify the elements
end
The Periodic Table
Mendeleev’s Periodic Table: Elements with similar properties were placed in
the same column The mass of the elements increased along
each row
end
The Periodic Table
Mendeleev left several blank spaces in his periodic table These spaces were for elements that had not
been discovered yet Mendeleev predicted what properties these
elements would have based on the elements around them
end
The Periodic Table
The Modern Periodic Table: Based on Mendeleev’s table Elements with similar properties are in the
same column Columns are called GroupsNumbered 1 to 18 (from left to right)
Atomic Numbers (# of protons) increase going across the table
Rows are called PeriodsNumbered 1 to 7 (from top to bottom)
end
The Periodic Table•This is the full Periodic Table
• As you can see it is REALLY long
• Way too long to fit on a page
end
The Periodic Table
•In order to make everything fit on 1 page, we take out the Lanthanides and Actinides.
•They are moved to the bottom of the table end
The Periodic Table
Metals Left of the stair-step line Francium (Fr) is the most reactive
Moving away from Fr, metals become less reactive Good conductors of electricity and heat Mostly solids at room temperature
High melting and boiling points Malleable and ductile
end
The Periodic Table
NonmetalsRight of the stair-step lineFluorine (F) is the most reactive nonmetal
Moving away from F, nonmetals become less reactive
Poor conductors of heat and electricityMostly gases at room temperature
Low melting and boiling points
Not malleable and not ductile
end
The Periodic Table
Metalloids Touching the stair-step line Have properties that fall between those of metals
and nonmetalsThis depends on the temperature
end
The Periodic Table
Alkali Metals Group 1 EXTREMELY REACTIVE!
Alkaline Earth Metals Group 2
end
The Periodic Table
• Transition Metals– Groups 3 to 12– Have a wide variety of properties
• Lanthanide and Actinide Series– At the bottom of the table– All are radioactive
end
The Periodic Table
Halogens Group 17 Highly Reactive
Noble Gases Group 18 Extremely Unreactive
THEY DO NOTHING!
end
The Periodic Table• Atomic Size
– Francium (Fr) is the largest atom– Helium (He) is the smallest atom– The closer to Fr, the larger the atom
• Valence Electrons– Electrons in the highest energy level– These give elements their chemical properties
Group: 1 2 13 14 15 16 17 18
# of 1 2 3 4 5 6 7 8
Valence:
end