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According to Dalton, what combines in whole-number ratios to form compounds?
Electrons
Nuclei
Elements
Atoms
Which idea from Dalton helped explain why chemical reactions always follow the same proportions?
Atoms have isotopes
Atoms are indivisible
Atoms combine in fixed ratios
Atoms have a nucleus
What evidence showed Thomson that the particles in the cathode ray had mass?
They bounced off the tube walls
They traveled in circles
They emitted light
They cast a shadow
What caused the cathode ray to bend in Thomson’s experiment?
emperature changes
A chemical reaction
Electric and magnetic fields
Gravity
What charge did Thomson conclude the particles in the cathode ray carried?
Negative
Neutral
Changing
Positive
Millikan suspended oil droplets between charged plates. What force pulled the droplets downward?
Light pressure
Friction
Gravity
Electromagnetic force
Millikan adjusted the electric field until droplets stopped falling. What did this allow him to determine?
The droplet’s volume
The speed of the droplet
The nucleus’s size
The electron’s charge
Millikan’s data showed that the electron’s charge was always a multiple of one small value. This proved that charge is:
Changing with temperature
Random
Increasing
Constant and quantized
In Rutherford’s experiment, what would the plum-pudding model have predicted?
All alpha particles bounce back
Even scattering
Almost no deflections
Heavy deflections
The fact that a few alpha particles bounced back suggested the nucleus was:
Very large
Spread out
Dense and positive
Negatively charged
Which part of the atom takes up most of its space?
Proton field
Neutron layer
Nucleus
Electron cloud
Which scientist provided the first experimental evidence that atoms are not solid spheres?
Dalton
Thomson
Millikan
Rutherford
Which observation from Rutherford supported the existence of a nucleus?
Oil droplets floated
Cathode rays glowed
Electrons traveled in circles
A few alpha particles rebounded
What type of radiation did Rutherford use?
Beta particles
Electrons traveled in circles
Gamma rays
Alpha particles
What did all four scientists ultimately show about atomic models?
They improve as new evidence appears
They are all correct
They are guesses
They never change
Which scientist first suggested atoms were the smallest unit of matter?
Rutherford
Thomson
Dalton
Millikan
