Honors Chemistry - Unit 3 - Matter & Atomic Theory
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109 Terms
What are allotropes?
A different form of an element
What are the allotropes for oxygen?
Oxygen Gas, Ozone
What is the chemical formula for oxygen gas?
O2
What is the chemical formula for ozone?
O3
What are the allotropes for carbon?
Graphite, Diamond and Buckminsterfullerene
Name the 1st law of the atomic theory
Law of Definite Proportions
Definition of the Law of Definite Proportions
Any sample of a compound always has the same composition
Example of the Law of Definite Proportions
Water is ALWAYS 11.2% hydrogen (H) and 88.8% oxygen (O)
Name the 2nd law of the atomic theory
Law of Conservation of Mass
Definition of the Law of Conservation of Mass
Matter cannot be created or destroyed, only transformed
Example of the Law of Conservation of Mass
Sulfur (S) (32.07g) + Oxygen (O2) (32.00g) → Sulfur Dioxide (SO2) (64.07g)
Name the 3rd law of the atomic theory
Law of Multiple Proportions
Definition of the Law of Multiple Proportions
Different compounds have different mass proportions
Example of the Law of Multiple Proportions
N2O = (N)(N)(O) … NO2 = (O)(N)(O)
What did Democritis of Ancient Greece discover?
The idea that all matter is composed of atoms
At the time in 400 BC when Democritis discovered the composition of atoms, was it really science?
No, it was a philosophy
What does the word “Atom” come from?
The Greek word, “Atomos”
What does Atomos mean?
Uncuttable
What did John Dalton discover?
The 1st Atomic Theory (based on actual evidence)
All matter is made of indivisible atoms
Yes and no
All atoms of an element are identical
Yes and no
Atoms of different elements have different physical and chemical properties
Yes
Atoms of different elements combine in simple, whole number ratios to form compounds
Yes
Chemical reactions consist of the combination, separation and rearrangement of atoms
Yes
What was Dalton’s atom like?
A marble
Why was Dalton’s atom like a marble?
Indivisible (no different paths)
Indestructible
Was Dalton correct about his marble theory regarding atoms?
Yes and no
Why was Dalton correct and incorrect about his marble theory regarding atoms?
Scientific theories change with new evidence
What did JJ Thomson discover?
The electron, the first subatomic particle
How did JJ Thomson discover electrons?
Through using a cathode ray tube.
What did Thomson discover about the “light” inside of the cathode ray tube?
“Light” was affected by a magnet/charged plates (attracted to +, repelled by, -)
How did Thomson calculate the mass of the particles?
He used the charge to mass ratio.
Within the cathode ray tube, what types of metals/gases gave the same exact results?
Different types
What charge do electrons have
negative
What was Thomson’s conclusion?
“The atom is not indivisible, the atom consists of smaller particles”
If atoms are neutral, then there…
must be something positive inside the atom to balance the charge
What was Thomson’s atom called?
Plum Pudding Model
Describe the plum pudding model
The electrons were embedded a sphere of positive charged
What did Ernest Rutherford discover?
Nucleus of an Atom
What was Rutherfords’ Gold Foil Experiment?
involved firing alpha particles at a thin gold foil, expecting most to pass through with minimal deflection. However, the unexpected finding was that a small fraction of particles were deflected at large angles, and a few even bounced back.
What are alpha particles?
massive, positively charged particles released by radioactive materials.
What was expected of the Gold Foil Experiment?
Expected most alpha particles to pass through gold foil with minimal deflection
Why did Rutherford expect for alpha particles to pass through gold foil with minimal deflection?
Plum pudding model was the accepted model at the time (positive charge was too diffuse)
What were the actual results of Rutherford’s experiment?
1 in 8000 alpha particles deflected back
Why did 1 in 8000 alpha particles bounce back?
The alpha particle shit something that was positively charged, massive, and took up very little space (volume)
What does Rutherford’s nuclear atom look like?
The nucleus is positively charged, most of the atom’s mass, tiny part of an atom’s volume,
What is the density of the nucleus of the atom
(2.3 × 10^14 g/cm³)
The atom is mostly…?
Empty space!
If the atom were a size of Soldier Field, then the nucleus would be as big as…
A marble on the 50 yard line…
Did John Dalton, JJ Thomson, or Ernest Rutherford have a good understanding of electrons?
No!
What was Dalton’s conclusion on electrons?
“What’s an electron?”
What was Thomson’s conclusion on electrons?
“Electrons are embedded in a sphere of positive charge”
What was Rutherfords’s conclusion on electrons?
“Electrons are like planets around a star”
What is the modern atom like?
A nucleus with protons and neutrons inside of an electron cloud with electron particles.
What is the size of the nucleus of an atom
10^-13 cm
What is the size of an atom
10^-8 cm
What are the 3 different subatomic particles within an atom?
Electron
Proton
Neutron
What charge does an electron have
-1 charge
What charge does an proton have
+1 charge
What charge does an neutron have
neutral charge
What is the mass of an electron
0.000549 = 0
What is the mass of an proton
1.007276 = 0
What is the mass of an neutron
1.008665 = 1
Where is the electron located in the atom?
Electron cloud
Where is the proton located in the atom?
Nucleus
Where is the neutron located in the atom?
Nucleus
Definition of Isotopes
Atoms with the same # of protons BUT different # of neutrons
What does the symbol “p+” stand for?
Proton
What does the symbol, “e-” stand for?
Electron
What does the symbol, “n0” stand for?
Neutron
How does one find the Proton #?
Proton # = Atomic #
How does one find the Electron # of a NEUTRAL ATOM?
Electron # = Protons #
What is a charged atom
Ion
What is a positively charged ion
Cation
What is a negatively charged ion
Anion
How does one find the Electron # of a POSITIVELY CHARGED ION?
Electron # = Proton # - positive charge.
How does one find the Electron # of a NEGATIVELY CHARGED ION?
Electron # = Proton # + negative charge.
How does one find the Neutron #?
Neutron # = Mass # - Proton #
How does one find the Average Atom Mass #?
Average Atom Mass # = Proton # + Neutron #
All matter is made of…
tiny, little particles
Atom
basic unit of matter
How many different types of atoms are there
118
What is an element?
simplest substance, made only 1 type of atom
symbols (1 or 2 letters, watch your capitalization)
Examples of elements
Oxygen (O), Hydrogen (H), Nitrogen (N), etc.
The universe is exactly how much of H (hydrogen)?
90%
Living things are made mostly out of what 4 elements?
Oxygen (64%)
Carbon (18%)
Hydrogen (10%)
Nitrogen (3%)
When you hear organic, think…
carbon!
What is a compound?
compound of at least 2 different atoms bonded together
Examples of compounds
Caffeine (C8 H10 N4 O2), Table Salt (Sodium Chloride) (NaCl)
Elements & compounds are what kind of substances?
Pure
What does it meant when elements and compounds have a pure substance?
They have a constant composition.
What is a mixture?
2 or more pure substances physically mixed together (not bonded)
What is a homogeneous mixture
Components are uniformly distributed (looks the same throughout)
Examples of homogeneous mixtures
Salt water, Air, 14 karat gold
What is another name for a homogeneous mixture?
Solution!
What is a heterogeneous mixture
Components are not evenly distributed (you can see the different components)
Examples of heterogeneous mixtures
Oil & water, orange juice, blood
What is distillation?
Separation technique of a liquid mixture that depends on a difference in boiling points.
What mixture does distillation work for?
Homogeneous mixtures
What is filtration?
Separation technique of a heterogeneous mixture