Early Atomic Models
He was the first to suggest that matter is made of tiny, indivisible particles called “atomos.”
Democritus
The cathode ray tube experiment led to the discovery of which particle?
the electron
This subatomic particle has a positive charge.
Proton
Two atoms of the same element with different numbers of neutrons are called what?
Isotopes
The unit used to measure atomic mass.
Atomic mass unit (amu)
Dalton’s model described atoms as these kinds of solid objects.
Solid spheres
This scientist suggest that the structure of atoms were somehow related to electricity. Inspiring future chemists.
Michael Faraday
This subatomic particle has no charge and is found in the nucleus.
neutron
When an atom gains or loses electrons, it becomes this.
Ion
The average atomic mass of an element depends on the mass and this property of each isotope.
Relative abundance (percent abundance)
J.J. Thomson’s “plum pudding” model pictured the atom as a sphere of positive charge with these scattered throughout.
Electrons
Draw the plum pudding model
(ans. vary)
These two subatomic particles have approximately the same mass.
proton and neutron
A sodium atom that loses one electron becomes what kind of ion (name and charge)?
Na+
The instrument used to measure the relative abundance of isotopes.
Mass spectrometer
Rutherford’s gold foil experiment led to the discovery of this part of the atom.
The nucleus
This is how Rutherford discovered there is a nucleus.
Gold Foil experiment
This subatomic particle orbits the nucleus.
Electron
Which subatomic particle changes when an isotope forms?
neutrons
An element has two isotopes: 25% with a mass of 10 amu and 75% with a mass of 11 amu. What is its average atomic mass?
10.75 amu
In Bohr’s model, these move in these specific circular paths or energy levels around the nucleus.
electrons
These were the two phenomona observed during cathode ray tube experiments.
could move a paddle wheel
magnets would deflect the ray
Which subatomic particle determines the identity of an element?
proton
How many protons, neutrons, and electrons are in Cl⁻ with a mass number of 35?
Protons: 17
Neutrons: 18
Electrons, 18
Explain why the atomic mass listed on the periodic table is rarely a whole number.
It’s a weighted average of all naturally occurring isotopes of that element.