Chapter 3 Scientist
The Scientists
Niels Bohr
What subatomic particles did he study?
The electron the electrons and the nucleus
Where are these subatomic particles located?
Electrons are located in fixed circular orbits and the nucleus the nucleus is located at the very center of the atom
What did he learn about these subatomic particles?
Electrons orbit the nucleus at specific allowed distance the angular momentum of an electron in its orbit is restricted to b be specific while numbers
What do these particles have to do with energy?
Each particle corresponds to a specific energy level
Based on this information, sketch a diagram of the atom?
James Chadwick
What subatomic particles did he study?
He studied the neutron, which he also discovered
Where are these subatomic particles located?
In the atom, it is located in the nucleus
What did he learn about these subatomic particles?
He learned that the neutron has no electrical change. The mass of the neutron is similar to the mass of the proton. Since there is no charge, it can pass through heavy atomic barriers without getting rejected
Based on this information, sketch a diagram of the atom?
Marie Curie
What did she discover about the atomic structure of an atom?
She found that radiation strength depended only on the quantity of uranium or thorium in a sample, regardless of the chemical compound or how atoms were arranged into molecules
What did she discover about nuclear radiation?
She discovered and named polonium and radium in 1898 by observing that uranium ores like pitchblende were far more radioactive than pure uranium could account for. She established that radioactivity is an atomic property
John Dalton
He had four major points (postulates or hypotheses) about atoms, what were these points?
• Indivisibility: Matter is composed of exceedingly small, indivisible particles called atoms.
• Identity: All atoms of a given element are identical in mass and properties.
• Combination: Atoms of different elements combine in simple, whole-number ratios to form chemical compounds.
• Conservation: Chemical reactions involve the rearrangement of atoms; atoms are neither created nor destroyed.
Louis de Broglie
What subatomic particles did he study?
He focused almost entirely on electrons
Where are these subatomic particles located?
They are found in the region outside and surrounding the nucleus of an atom what we called a cloud
What did he learn about these subatomic particles?
He discovered wave particle duality for matter. This means electrons aren't just solid little dots; they behave like waves of energy while they move
What do these particles have to do with energy?
An electron energy determines its wavelength. Because an electron has to fit perfectly around the nucleus as a stable standing wave it can only exist at specific quantized energy levels if it doesn't have the exact right energy the wave cancels itself out and disappears
Based on this information, sketch a diagram of the atom?
Werner Heisenberg
What subatomic particles did he study?
electrons
Where are these subatomic particles located?
• Electrons are located outside the atomic nucleus in the electron cloud.
• Protons and neutrons are located inside the nucleus at the center of the atom.
What did he learn about these subatomic particles?
He discovered the Heisenberg Uncertainty Principle. This fundamental law of quantum mechanics states that it is impossible to simultaneously know both the exact position and the exact momentum (velocity) of a subatomic particle like an electron. The more precisely you measure one property, the less precisely you can know the other.
Dimitri Mendeleev
What are some of his major contributions to chemistry?
The Periodic Table: In 1869, he organized the 63 known elements into a tabular format based on their properties.
How did he use atomic structure in his discoveries?
• Predicting Undiscovered Elements: He left intentional gaps in his table for elements that had not yet been found (such as gallium, scandium, and germanium) and accurately predicted their atomic masses and chemical properties.
Robert Millikan
What subatomic particles did he study?
The electron
Where are these subatomic particles located?
Outside the nucleus in the electron cloud
What did he learn about these subatomic particles?
He measured the charge of a single electron in his oil drop experiment he found the eclectic charge is quantized rather than a continuous range the charge of a single electron is approximately 1.6 x 10^-19 coulombs
Explain the Oil Drop Experiment.
• The Setup: An atomizer sprayed a fine mist of oil droplets into an upper chamber. Some drops fell through a small hole into a lower space between two parallel metal plates (one on top, one on the bottom).
• Measuring Mass: With no electric field turned on, gravity pulled the drops down. Air resistance (viscous drag) slowed them until they reached a steady fall speed (terminal velocity). By watching a drop fall through a microscope, Millikan calculated the size and mass of the droplet.
• Adding Charge: X-rays were shone through the chamber to ionize the air. Electrons from the air attached to the falling oil drops, giving the drops a negative electric charge.
• Balancing Forces: A voltage was applied to the metal plates to create an electric field. By adjusting the voltage, the upward electric force was balanced with the downward gravitational force, suspending the oil drop in mid-air
Ernest Rutherford
What subatomic particles did he study?
Protons, alpha particles, electrons
Where are these subatomic particles located?
Inside the nucleus of an atom outside the nucleus in the empty space surrounding the nucleus
What did he learn about these subatomic particles?
Positive charge is all packed into the nucleus the rest of the atom is filled with negatively charged electrons
Describe the Gold Foil experiment.
He aimed a beam of alpha particles at a sheet of gold foil. There was also a detector screen that surrounded the foul and was able to direct the alpha particles when the particles hit the screen it would make a tiny flash of the light. The piece of foil was then placed in front of the beam
Based on this information, sketch a diagram of the atom?
Erwin Schrodinger
What subatomic particles did he study?
(electrons, protons, or neutrons)
He studied electrons
Where are these subatomic particles located?
The electrons were found in the electrons could surrounding the nucleus
What did he learn about these subatomic particles?
He learned that they behave like waves and it is impossible to know an electron's exact position and momentum at the same time
Make sure to have his equation on your poster.
J.J. Thomson
What subatomic particles did he study?
Electron positive ions and stable isotopes
Where are these subatomic particles located?
Outside the positive nucleus of an atom electron cloud
What did he learn about these subatomic particles?
Cathode rays are made up of electrons found inside every atom electrons are universal building blocks of all matter
Describe the Cathode Ray experiment.
1897was a grounding breaking physics experiment that led to the discovery of the electron fist he used a magnet and electrometer to observe that the cathode rays were indeed electrically charged next he determined that cathode rays were negatively charged by observing they bend away from a negatively charged metal plate and toward a positively charged one. Lastly by measuring the mass to charge ratio of cathode ray he found that they were composed of subatomic particles
Make sure to have a picture of his experiment.
Joseph Proust
What law is he credited with in chemistry?
He is credited with the Law of Definite Proportions (also known as the Law of Constant Composition or Proust's Law).
What does it say?
in a fixed and definite ratio by mass, regardless of how the compound was prepared or where it was obtained.
What did Proust work with in his experiments? (water, lead, mercury, or something else?)
Proust worked with lead, mercury, and something else. Specifically, his most famous experiments involved analyzing metallic oxides, sulfides, and carbonates (such as copper carbonate, iron sulfides, and tin oxides). In his findings, he explicitly highlighted that metals like lead and mercury combine with oxygen in constant, definite proportions.
Was his Law of Constant Composition accepted or rejected when it was first published?
It was initially rejected and heavily contested when first published. A prominent French chemist named Claude Louis Berthollet fiercely opposed it, arguing that elements could combine in variable proportions. The dispute lasted for years until John Dalton's atomic theory provided a theoretical baseline that supported Proust, leading to its widespread acceptance by around 1811–1812.
Antoine Lavoisier
What law is he credited with in chemistry?
Given Credit for the Law Of Conservation Of Mass.
What does it say?
The Law Of Conservation Of Mass States that mass cannot be created nor destroyed.
What element is he given credit with discovering in combustion?
He named Oxogyn and recognized hydrogen as an element in H20.
Did he mostly work with solids, liquids, or gases?
He mainly worked with gases, especially oxygen & Hydrogen.
How did he die?
Antoine Lavoisier was executed by guillotine on May 8th, 1794 because of his former role as a private tax collector for the hated Ferme Géné rale during the French Revolution Reign of Terror.
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