Chapters 3 & 21- Atoms and Nuclear Chemistry Flashcards
Which Greek supported the particle theory of matter?
Democritus
What did Democritus call nature’s basic particle?
An atom
What does atom mean in greek?
Indivisible
What did Aristotle believe about the nature of matter?
All matter was continuous
What is the law of conservation of mass
Mass is neither created nor destroyed during ordinary chemical reactions or physical changes.
Who reason that elements were composed of atoms in the early eighteen hundreds?
John Dalton
Define an atom.
The smallest particle of an element that retains the chemical properties of that element.
What is a cathode ray tube?
A vacuum tube that transmits a beam of electricity from the negative (cathode) end to the positive (anode) end when a voltage is applied.
What experiment did JJ Thomson do with a cathode ray tube?
He applied a magnetic field to the cathode ray. The cathode ray was attracted to positive charges in the magnetic field, meaning that the cathode rays are streams of negatively charged particles.
What did JJ Thomson discover?
The electron
What did Robert Millikan do?
He used an oil drop apparatus to determine the charge and mass of an electron.
What is the mass:mass ratio of an electron to a hydrogen atom?
1/1840
Describe Thomson’s “plum pudding” model of the atom
An atom is a sphere of uniform positive charge in which electrons reside
Describe the experiment Rutherford performed to test the plum pudding model.
He measured alpha particles deflection through a thin gold foil. He observed that some alpha particles deflected at large angles or bounce straight back.
What were the results of Rutherford’s experiment?
Since the alpha particles were repelled by another positively charged thing, he created the nucleus
Describe Rutherford’s model of the atom.
Atoms are mostly empty space. Most of an atom’s mass is at the center in the nucleus. Positively charged particles in the nucleus are protons. Electrons move in the empty space.
What particle inside the nucleus of an atom has no charge?
Neutrons
What is an atomic number
The number of protons and electrons in each atom of an element.
What is a mass number
The total number of protons and neutrons that make up the nucleus of an atom.
What is an isotope
Atoms of the same element that have different masses (have different numbers of neutrons)
How do you calculate the average atomic mass of isotopes
Multiply element # by percent (making sure u moved the decimal 2 spots) and adding with another
What is radioactive decay
Spontaneous disintegration of a nucleus into a lighter nucleus with release of particles or electromagnetic radiation
Why isn’t the atomic mass the same if the number of protons and neutrons is always a whole number on the periodic table
The atomic mass is the weighted average of the naturally occurring isotopes
What is an alpha particle
Two protons and two neutrons bounced together, emitted from the nucleus
