16 flashcards · Shared on 19 August 2026 by AtomAI Library
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How does the relative mass of an electron compare with those of protons and neutrons?
It is much smaller than both
How does the relative mass of an electron compare with those of protons and neutrons?
It is much smaller than both
A neutral atom has an atomic number of 12. How many electrons does it have?
12
Which statement defines isotopes of an element?
Atoms with the same proton number but different neutron numbers
What model of the atom was tested by Rutherford's alpha-particle scattering experiment?
The plum pudding model
In Rutherford's experiment, what happened to most alpha particles directed at thin gold foil?
They passed straight through or were only slightly deflected
A small fraction of alpha particles were deflected through large angles. What did this show?
The atom's positive charge is concentrated in a small region
What does the mass number of an atom represent?
The total number of protons and neutrons in its nucleus
An atom has mass number 23 and atomic number 11. How many neutrons are in its nucleus?
12
What keeps negatively charged electrons associated with the positively charged nucleus?
Electrostatic attraction between opposite charges
What is the atomic number of an element?
The number of protons in the nucleus
What conclusion followed from most alpha particles passing through the foil?
Atoms are mostly empty space
Why were a very small number of alpha particles scattered almost straight back?
They passed close to a small, dense, positively charged nucleus
Which description best matches the nuclear model of the atom?
A tiny, dense, positively charged nucleus surrounded by electrons
Which particles are found in the nucleus of an atom?
Protons and neutrons
What are the relative charges of a proton, neutron and electron, respectively?
+1, 0, −1
Where is most of an atom's mass concentrated?
In its nucleus