Atomic Structure 1
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91 Terms
What is a scientific theory
A well-substantiated explanation of a natural phenomenon based on repeated observations and experiments
Are scientific theories guesses
No they are reliable accounts of the real world
What do scientific laws describe
What happens in a given situation often with equations
What do scientific theories describe
Why and how phenomena occur
What supports scientific laws and theories
Observations and experimental evidence
What must be true for a theory to be accepted
Experiments must be repeatable and reproducible
What else is required for theory acceptance
Consensus within scientific community
What must link evidence to theory
Strong empirical evidence congruent with theory
What must data be
Accurate and reliable
Can theories be proven false
Yes they must be falsifiable
Difference between laws and theories
Laws describe what happens theories explain why
Do laws change often
No unless major error discovered
Do theories change
Yes they evolve with new evidence
What is a hypothesis
A tentative explanation that can be tested
What is a scientific law
A statement summarizing relationships between variables
What is an experiment
A controlled method to test a hypothesis
What is the scientific method
A process involving observation experimentation and analysis
Step 1 of scientific method
Make observations
Step 2 of scientific method
Formulate hypothesis
Step 3 of scientific method
Test hypothesis
Step 4 of scientific method
Accept or modify hypothesis
Step 5 of scientific method
Develop law or theory
What is the law of conservation of mass
Mass is neither created nor destroyed in chemical reactions
Who proposed conservation of mass
Antoine Lavoisier
What does conservation of mass mean in reactions
Total mass of reactants equals total mass of products
What type of system applies to conservation of mass
Closed system
What is the law of constant proportion
A compound always contains same elements in same mass ratio
Who proposed law of constant proportion
Joseph Proust
What did Democritus propose
Atoms differ in shape size and mass
Did Democritus have experimental evidence
No
What is Dalton’s atomic theory
Theory stating matter is made of atoms with specific properties
Dalton postulate 1
All matter is made of atoms
Dalton postulate 2
Atoms are indivisible and indestructible
Dalton postulate 3
Atoms of same element are identical
Dalton postulate 4
Atoms combine in fixed ratios
Dalton postulate 5
Chemical reactions rearrange atoms
What law supports Dalton’s theory
Conservation of mass
What is definite composition
Compounds have fixed ratio of elements by mass
Merit of Dalton theory
Explained laws of chemistry
Another merit of Dalton theory
Distinguished elements and compounds
Flaw of Dalton theory
Atoms are divisible into subatomic particles
What are isotopes
Atoms of same element with different masses
Another flaw of Dalton theory
Incorrect formulas like OH for water
Another flaw
Cannot explain complex compounds
Another flaw
Cannot explain allotropes
What did Thomson discover
The electron
What experiment did Thomson use
Cathode ray tube
What charge are cathode rays
Negative
What did Thomson model
Plum pudding model
What is plum pudding model
Electrons embedded in positive charge
Limitation of Thomson model
Did not identify positive particles
Who discovered protons
Goldstein
What experiment showed protons
Anode ray experiment
What condition produced glow in tube
Low pressure gas
What does neutral atom require
Positive and negative charges
What did Rutherford experiment use
Gold foil experiment
What particles were used
Alpha particles
Observation 1 of Rutherford
Most particles passed through
Conclusion
Atom is mostly empty space
Observation 2
Some particles deflected
Observation 3
Few bounced back
Conclusion of Rutherford
Mass concentrated in nucleus
What is Rutherford model
Electrons orbit nucleus like planets
Who discovered neutron
Chadwick
How were neutrons discovered
Bombarding beryllium with alpha particles
Why are neutrons neutral
Not deflected by fields
Where are neutrons located
In nucleus
What is Bohr model
Electrons move in fixed energy levels
Why was Bohr model needed
Rutherford model unstable
What happens when electron changes level
Energy emitted or absorbed
What is lowest energy state
Ground state
What happens when electron drops level
Photon emitted
What is atom
Smallest unit of element retaining properties
What is atomic number
Number of protons
What is mass number
Protons plus neutrons
What is relative atomic mass
Average mass relative to carbon-12
What are isotopes
Same protons different neutrons
What is relative molecular mass
Sum of atomic masses in molecule
What particles make atom
Protons neutrons electrons
Charge of proton
+1
Charge of electron
-1
Charge of neutron
0
Mass of proton
1
Mass of neutron
1
Mass of electron
1/1840
Location of proton
Nucleus
Location of neutron
Nucleus
Location of electron
Orbital
Who discovered electron
Thomson
Who discovered proton
Rutherford
Who discovered neutron
Chadwick