Module 3 Test Flashcards
What 4 things did early philosophers believe matter was composed of?
Earth, water, air, and fire.
Why did Democritus’s ideas about matter go against other philosophers beliefs?
Because Democritus could not answer the question of “What holds the atoms together?”.
Why were Democritus’s ideas about matter widely rejected?
Aristotle rejected the notion of atoms because it went against his beliefs. Aristotle was very influential at this time so many continued to reject Democritus’s ideas as well.
What was the book A System of Chemical Philosophy published by John Dalton about?
Describes how Dalton revisited and revised Democritus’s ideas and worked to determine the mass ratios of the elements involved in the experiments Dalton conducted.
Who was John Dalton?
John Dalton was a schoolteacher in England that developed the modern atomic theory by reviving and revising Democritus’s ideas by his performed experiments.
Why do you think John Dalton is important in understanding atoms?
Because his modern atomic theory explains that the conservation of mass in chemical reactions is the result of the rearrangement of atoms during the reaction.
What is an atom?
An atom is the smallest particle of matter that retains the properties of the element.
How do we know atoms exist?
Many experiments have been conducted since Dalton’s time to prove that atoms exist.
What is a cathode ray tube for?
It is used to help researchers study the relationship between mass and charge.
What is an electron?
An electron is a negatively charged particle that is a part of all forms of matter.
Who is J.J. Thomson?
J.J. Thomson was the first to identify the first subatomic particle, the electron.
How did J.J. Thomson identify the electron?
He did this by determining the charge-to-mass ratio of the charged particle, then compared that ratio to other known ratios.
Which of Dalton’s theories did J.J. Thomson disprove?
Thomson disproved Dalton’s theories about atoms not being divisible. His discovered proved Dalton incorrect because atoms can be divided into smaller subatomic particles.
What did Ernest Rutherford prove?
Rutherford proved that Thomson’s plum pudding model was incorrect because it did not match the results of his Gold experiment.
What did Rutherford contribute to atomic theory?
His results from the gold experiment proved that an atom has a positive charge and mass contained in the center of the atom.
What did Rutherford discover?
He discovered that atoms have a nucleus and protons/
Who discovered the neutron?
James Chadwick
What are quarks?
The first experimental evidence for subatomic particles, subatomic particles that make up the composition of the structures for protons and neutrons
Who is Henry Moseley and what did he contribute to atomic theory?
He was an English scientist that discovered atomic number, which explains that the number of protons in an atom identifies it as an atom of a particular element.
What does periodicity have to do with how the periodic table is structured?
The periodic table is organized left-to-right and top-to-bottom by increasing atomic number. This pattern of order within the periodic table is called periodicity.
Where is the atomic number listed on an element on the periodic table?
The atomic number is listed to the left or on top of the element’s symbol on the periodic table.
Where is the atomic mass listed on an element on the periodic table?
The atomic mass is listed below the element’s chemical name at the bottom of each element on the periodic table.
What is an isotope?
An isotope is an atom with the same number of protons but different number of neutrons.
What is the law of definite proportions?
A chemical in a compound always contains the same elements in exactly the same proportions by weight or by mass.
What is the law of conservation of mass?
Mass cannot be created nor destroyed in chemical or physical changes.
What law does this prove?
NaCl= 39.34% of Na and 60.66% Cl 1:1 ratio of Na to Cl
The law of definite proportions
What law does this prove?
30 kg of wood + 1 kg of fire —> 28 kg of ashes + 3 kg of smoke
The law of conservation of mass
What is the law of multiple proportions?
When two elements combine to form two or more compounds, the mass of one element that combines with a given mass of the other is in the ratio of small whole numbers
What law does this prove?
CO CO2
Mass of C 12g 12g
Mass of O 16g 32g
Ratio C:0 1:1 1:2The law of multiple proportions
What is a proton?
A subatomic particle that ha a positive charge and is found in the nucleus of an atom
What is a neutron?
A subatomic particle that has a neutral/ no electric charge and is found in the nucleus of an atom
What is an electron?
A subatomic particle that has a negative electric charge and is found in the electron cloud surrounding the nucleus
What did Democritus suggest?
Suggested “indivisible” pieces of matter called atomos (atoms)
What did Aristotle believe?
Believed that matter was composed of air, water, fire, and earth, this attacked Democritus’s ideas and halted the progress of the atom for over 2,000 years
What did Dalton do with Democritus’s beliefs?
Revised them and determined elements were made of one kind of atom and they could combine to form compounds
What did Dalton and Democritus agree on?
Atoms took the shape of solid spherical balls
What are some of Dalton’s atomic theory principles that are always true?
Atoms of different elements differ in their physical and chemical properties.
Atoms of different elements combine in simple, whole-number ratios to form compounds.
In chemical reactions, atoms are combined, separated, or rearranged but never created, destroyed, or changed.
In Thomson’s plum pudding model, what were the electrons?
The electrons were the negatively charged particles that “floated” through the pudding
In Thomson’s plum pudding model, what were the protons?
The protons were the positively charged pudding
What did Thomson discover?
Electrons
What did Thomson use to discover electrons?
The cathode ray tube
What did Rutherford discover?
Most of the atom is empty space with a nucleus in the center
What are the remaining principles of Dalton’s theory that were proved to be not always true?
All matter is composed of extremely small particles called atoms which cannot be subdivided, created, or destroyed.
Atoms of given elements differ in their physical and chemical properties.
Ernest Rutherford was a student of JJ Thomson. When he got his own lab, he took on 2 students: Hans Geiger and Ernest Marsden, along with one of Thomson’s students Niels Bohr. What was the name of their famous experiment?
Gold Foil Experiment
So in the plum pudding model of the atom, the “dough” was actually a ____ charged sea.
Positively
When they shoot alpha particles at the gold foil, where do most of them go?
Right through the foil as if nothing is there.
What would make the alpha particles bend away from the center?
They are deflected by other positively charged particles in the atom
What would make alpha particles bounce right back?
They hit a positively charged particle head on (like a billiard ball hitting another head on)
What is an alpha particle?
Positively charged radioactive particle
What were some problems with Rutherford’s model?
The model believed electrons orbit around the nucleus like planets around the sun.
Opposites attract, so the positively charged nucleus should attract the negatively charged electrons.
What was the main problems with Rutherford’s gold experiment?
He could not explain why the electrons do not crash into the nucleus.
Who tried to solve the question Rutherford could not answer?
Niels Bohr
How did Bohr try to solve Rutherford’s unsolvable question?
He proposed that electrons travel around the nucleus in specific energy levels that are each a certain distance from the nucleus
What did Bohr say that energy levels worked like?
Energy levels worked like rungs of a ladder
Why do energy levels work like rungs on a ladder?
You can only stand on the rungs, not in between the spaces.
In relation, electrons can only be in one energy level or another not in between.
What was the last subatomic particle to be discovered?
The neutron
