Chemistry - Central Science C2
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49 Terms
Law of Conservation of Mass
The total mass of materials present before and after a chemical reaction is the same
Cathode Rays
Streams of electrons
What Fields describe
How force acts and propagate
what Energy quantifies
The capacity of forces to produce changes
Charge of an electron
-1.602e-19 C
Electron Mass
9.10e-28g
Charge of α particles
Positive (2+)
Charge of β particles
Negative (1-)
Gamma Radiation
A high energy electromagnetic radiation similar to X rays
Thomson Model other name
The plum pudding model
Alpha particles are also known as
Helium nuclei is also known as
Why did J.J. Thomson conduct his cathode ray tube experiment?
Thomson aimed to determine whether cathode rays were particles or waves and to explore the internal structure of atoms
Setup of J.J. Thomson CRT experiment
A sealed glass tube a cathode, an anode, and high voltage created a beam of cathode rays.
Observations from J.J. Thomson CRT experiment
Cathode rays carried negative charge, had mass, and behaved identically regardless of materials
What did J.J. Thomson calculate calculate in his CRT experiment?
Thomson calculated the charge-to-mass ratio of electrons
What were the consequences of J.J. Thomson’s cathode ray tube experiment?
The experiment led to the discovery of the electron, disproved indivisible atoms, and introduced the Plum Pudding Model of atomic structure.
Why did Robert Millikan conduct the oil drop experiment?
He aimed to measure the charge of an electron
What was the setup of Millikan’s oil drop experiment?
A chamber with two charged plates was used to suspend tiny oil droplets, with their motion controlled by adjusting an electric field.
What did Millikan observe during the experiment?
By balancing the gravitational and electric forces, Millikan observed that oil droplets carried charges in discrete multiples of a fundamental value.
What did Millikan calculate in his experiment?
Millikan calculated the charge of a single electron as 1.6×10−19 C, confirming the quantization of electric charge.
What was calculated because of Millikan’s oil drop experiment?
The mass of an electron
Motivation for Rutherford’s Gold Foil Experiment
Rutherford wanted to test the Plum Pudding Model and understand the distribution of charge and mass in atoms.
Setup of Rutherford’s gold foil experiment
A beam of alpha particles was directed at a thin sheet of gold foil, with a detector placed around it to observe deflections.
Observations from the Gold Foil Experiment
Most alpha particles passed through the foil, some were deflected at small angles and others at large angles
Conclusions from Rutherford’s experiment
The atom has a dense, positively charged nucleus where most of its mass is concentrated, and the rest of the atom is mostly empty space.
Consequences of Rutherford’s gold foil experiment
The experiment disproved the Plum Pudding Model, led to the nuclear model of the atom, and laid the foundation for modern atomic physics.
Electronic Charge
1.602e-19 C
Charge of Electron
-1.602e-19 C
Charge of Proton
1.602e-19
What is the relationship between protons and electrons in a neutral atom?
They are in equal number
Cations
Atoms that have lost electrons
Anions
Atoms that gained electrons
How are electrons maintained near the nucleus
By electrostatic force between it and the nucleus
Atomic Mass unit (u)
1.66e-24 g
Isotopes
Variants of a chemical element that have different numbers of neutrons
How is the Atomic Mass Unit (u) defined?
It’s a one-twelfth of a Carbon-12 mass
What’s the average range of diameter of an atom?
30pm-300pm
What is an element’s atomic number?
The number of protons it has
Coulomb’s Law
The electric force between two charged particles is given by F = kQ_1Q_2/d²
What’s the relevance of gravitation force between atoms for chemistry?
None, since it is so small
What’s the force that holds the nucleus together?
Strong Nuclear Force
What does the subscript notation indicate when it comes before the symbol of element
The Atomic Number
What does the superscript notation indicate when it comes before the symbol of element
Mass Number (protons + neutrons)
Are the isotopes of a given element chemically alike?
Yes
Gold
Au
Strontium
Sr
Thomson’s Model description of atom
A sphere of positive charge with negatively charged electrons embedded within it
In Thomson’s model, is the mass evenly distributed?
Yes
Does Gamma Radiation consist of particles or carry charges?
No