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Student Version Periodic Table powerpoint with basic atomic theory. Isotope Lab. Why are the masses on the periodic table decimal values if they reflect “whole” protons and neutrons? How are the masses determined?. J ust when you thought it was only. Protons Neutrons And Electrons…. - PowerPoint PPT Presentation
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Student Version Periodic Table powerpoint with basic atomic theory
Why are the masses on the periodic table decimal values if they reflect “whole” protons and neutrons?How are the masses determined?
Just when you thought it was only
Protons Neutrons And Electrons…
“HA HA HA! It never stops! Never! There’s always more!You will never know it all! MUAH HAH HAH HAH! Always more!”
- THE ATOMIC THEORY
Vertical columns are Families -
elements with similar properties.
Alkali Metals
Alkaline Earth Metals
Transition Metals
Rare Earth Metals
Boron Family
Carbon Family
Nitrogen Family
Oxygen Family
Halogen Family
Nobel Gas Family
• How do you study something that is invisible?“Ya throw stuff at it n’see how it bounces off, duh!”
-Sam “Bhatman” Bhat, atomic researcher, politician, toe nail enthusiast
• Complete the projectile activity by using a straightedge and common sense to determine the shape of the invisible object inside the box.– Some projectiles pass straight through in one side and out the
other (they hit nothing).– Some projectiles go in, hit something, and are reflected back
out (dbl sided arrow)– Some projectiles go in, hit something, and are deflected out at
an angle. Retrace the paths and see where they intersect.
http://mogk12.2ya.com/rutherford
http://library.thinkquest.org/19662/low/eng/index.html
Atom – The Incredible World (Thinkquest)
Record what you observed, what you changed/did, what you learned for each virtual lab!
Download the worksheets and complete the lab and questions. Turn it in when you are done.
Virtual Labs• Interactives: http://phet.colorado.edu/ • Click “play with sims” then “chemistry” then “Run
Now”– States of Matter– Balloons and static electricity– Rutherford Scattering– Build an Atom – Tutorial and Game– Isotopes and Atomic Mass– Atomic Interactions– Models of the Hydrogen Atom
Record what you observed, what you changed/did, what you learned for each virtual lab!
You will hand in your labs!
Virtual Labs• http://www.rsc.org/chemsoc/visualelements/page
s/pertable_fla.htm (Visual Elements Periodic Table)
Dalton’s Model
• In the early 1800s, the English Chemist John Dalton performed a number of experiments that eventually led to the acceptance of the idea of atoms.
Dalton’s Theory• He deduced that all elements
are composed of atoms. Atoms are indivisible and indestructible particles.
• Atoms of the same element are exactly alike.
• Atoms of different elements are different.
• Compounds are formed by the joining of atoms of two or more elements.
.
• This theory became one of the foundations of modern chemistry.
Thomson’s Plum Pudding Model
• In 1897, the English scientist J.J. Thomson provided the first hint that an atom is made of even smaller particles.
Thomson Model
• He proposed a model of the atom that is sometimes called the “Plum Pudding” model.
• Atoms were made from a positively charged substance with negatively charged electrons scattered about, like raisins in a pudding.
Thomson Model• Thomson studied
the passage of an electric current through a gas.
• As the current passed through the gas, it gave off rays of negatively charged particles.
Cathode Ray Tube
Thomson Model
• This surprised Thomson, because the atoms of the gas were uncharged. Where had the negative charges come from?
Where did they come from?
Thomson concluded that the negative charges came from within the atom.
A particle smaller than an atom had to exist.
The atom was divisible!
Thomson called the negatively charged “corpuscles,” today known as electrons.
Since the gas was known to be neutral, having no charge, he reasoned that there must be positively charged particles in the atom.
But he could never find them.
Cathode Rays
Had mass – albeit a very small amount; they pushed a lightweight paddlewheel up an incline.
They could do work!
Had direction – they passed from the negative to the positive electrode
Had charge they bent in an electric field (towards the positive plate) and in a magnetic field
Rutherford’s Gold Foil Experiment
• In 1908, the English physicist Ernest Rutherford was hard at work on an experiment that seemed to have little to do with unraveling the mysteries of the atomic structure.
• Rutherford’s experiment Involved firing a stream of tiny positively charged particles at a thin sheet of gold foil (2000 atoms thick)
• http://chemmovies.unl.edu/ChemAnime/RUTHERFD/RUTHERFD.html
http://chemmovies.unl.edu/ChemAnime/RUTHERFD/RUTHERFD.html
Alpha Particles = He nucleus2p+ + 2no
– Most of the positively charged “bullets” passed right through the gold atoms in the sheet of gold foil without changing course at all.
– Some of the positively charged “bullets,” however, did bounce away from the gold sheet as if they had hit something solid. He knew that positive charges repel positive charges.
You Try
• The radius of a hydrogen atom is 5 x 10-11
meters. The radius of a single proton is 5 x 10-
16 meters. Assuming that atoms take the most size – efficient shape, a sphere, determine how much of an atom is truly empty space free of matter.
• Vsphere = 4/3 π r3
Rutherford vs Thomson• This could only mean that the gold atoms in the
sheet were mostly open space. Atoms were not a pudding filled with a positively charged material.
• Rutherford concluded that an atom had a small, dense, positively charged center that repelled his positively charged “bullets.”
• He called the center of the atom the “nucleus”• The nucleus is tiny compared to the atom as a whole.
Crammin’ Spark
You will have a quiz on the correct placement of elements on the table from memory.
You Try
• The radius of a hydrogen atom is 5 x 10-11
meters. The radius of a single proton is 5 x 10-
16 meters. Assuming that atoms take the most size – efficient shape, a sphere, determine how much of an atom is truly empty space free of matter.
• Vsphere = 4/3 π r3
Rutherford• Rutherford reasoned that
all of an atom’s positively charged particles were contained in the nucleus.
• The negatively charged particles were scattered outside the nucleus around the atom’s edge.
Bohr Model• In 1913, the Danish
scientist Niels Bohr proposed an improvement. In his model, he placed each electron in a specific energy level.
Where did I put my electrons?
Bohr Model• According to Bohr’s
atomic model, electrons move in definite orbits around the nucleus, much like planets circle the sun. These orbits, or energy levels, are located at certain distances from the nucleus.
The Wave Model• Today’s atomic
model is based on the principles of wave mechanics.
• According to the theory of wave mechanics, electrons do not move about an atom in a definite path, like the planets around the sun.
Wave Model
Electrons are defined by 3-D regions of probability where electrons are found “most” often
But where are they when they’re not where we expect?
A final word about Mendeleev’s Table…
• Mendeleev’s combining powers or valences• Metals do not form compounds with other
metals• Metals and non-metals react as do non-
metals with non-metals • How?• Why?• Who cares?
It’s the electrons
• The nucleus does not change.• The number of electrons do change
– Atoms become “ions” and they are attracted to oppositely charged particles
– Ions are named according to Faraday and his study of electrolytes (salt water) and conduction
• The combining powers that Mendeleev found reflect the amount of negative charge lost or gained during a reaction
The oxidation number of an element indicates the number of electrons gained or lost when forming compounds.
Elements with positive oxidation numbers lose electrons. (cation)
Elements with negative oxidation numbers gain electrons. (anion)
+1
+2
+1, +2, +3
+3
+4 or -4
-3
-2
-1
Electron energy levels, from 1 to 7
Electron energy sublevels
Electron energy sublevel s
Electron energy sublevel p
Electron energy sublevel d
Electron energy sublevel f
Each "pair" of boxes in a sublevelindicates an orbital. Each orbital can hold up to 2 electrons…
How many electrons fit in the 3rd energy level? What about the 4th?Count the boxes to find your answer…
3
4
8
18
An Electron Configuration showsthe exact location of every electronin an atom.1s2 2s2 2p6 = Configuration for Neon
With very few exceptions, theelectron configuration of an atomcan be read directly from the Table.
S block
P block
D Block
F block
Electron Energy Levels Match Up with the Rows of the Periodic Table