CA_Lesson_2_Defining+the+Atom Flashcards
What is the smallest particle of an element that retains the properties of the element called?
atom
The atom is the fundamental building block of matter.
What instrument allows individual atoms to be seen?
scanning tunneling microscope (STM)
The STM provides a way to visualize atoms on a surface.
What is a cathode ray?
A stream of particles carrying a negative charge known as electrons
Cathode rays are produced in a cathode-ray tube.
What was determined about the mass of the charged particle in cathode-ray experiments?
It was much less than that of a hydrogen atom
This finding contradicted Dalton’s theory that atoms are indivisible.
Who determined the charge of an electron using the oil-drop experiment?
Robert Millikan
Millikan’s experiment provided a precise measurement of the electron’s charge.
What is the mass of an electron?
9.1 x 10^-28 g
This mass is significantly smaller than that of protons and neutrons.
What model did J. J. Thomson propose?
The Plum Pudding Model
This model suggested a spherical atom with positive charge and embedded electrons.
What did Rutherford’s experiment involve?
Aiming alpha particles at a thin sheet of gold foil
The experiment tested the plum pudding model by observing particle deflection.
What did Rutherford conclude about the structure of the atom?
The atom has a dense, positively charged nucleus surrounded by negative electrons
This conclusion led to the nuclear model of the atom.
What is a proton?
A subatomic particle carrying a charge equal to but opposite that of an electron
Protons are found in the nucleus of an atom.
What is a neutron?
A subatomic particle that has a mass nearly equal to that of a proton but carries no electric charge
Neutrons also reside in the nucleus alongside protons.
True or False: Atoms are divisible into smaller subatomic particles.
True
This was a pivotal finding that changed the understanding of atomic structure.
Fill in the blank: The nucleus contains positively charged particles called _______.
protons
Protons are crucial for defining the element’s identity.
Fill in the blank: Almost all of an atom’s mass is contained in a tiny, dense region in the center called the _______.
nucleus
The nucleus is much smaller than the overall size of the atom.
What are the two main types of subatomic particles in the nucleus?
protons and neutrons
Electrons are located outside the nucleus.
