Subatomic Particles & Atomic Structure
What are the three main subatomic particles that make up an atom?
Protons, neutrons, and electrons
Who proposed the first modern atomic theory, describing atoms as solid spheres?
John Dalton
What makes two atoms isotopes of the same element?
They have the same number of protons but different numbers of neutrons.
What type of force attracts electrons to the nucleus?
Electromagnetic force
What do the rings in a Bohr model represent?
Electron energy levels
Which subatomic particle determines the element’s identity?
The number of protons
Which scientist discovered the electron using a cathode-ray tube?
J. J. Thomson
What does the mass number of an isotope represent?
The total number of protons and neutrons.
Which force keeps protons from flying apart inside the nucleus?
Strong nuclear force
How many electrons can fit in the first energy level of a Bohr model?
Two
Where is almost all of an atom’s mass located?
In the nucleus
What did Rutherford’s gold-foil experiment reveal about atomic structure?
That atoms are mostly empty space with a dense, positive nucleus.
Why do isotopes of the same element behave the same chemically?
Because they have the same number of electrons.
Why do electrons repel each other?
Because they have the same negative charge.
What do we call the electrons in the outermost energy level?
Valence electrons
Explain why atoms are mostly empty space.
Because the nucleus is tiny and dense while electrons occupy a large volume far from it
How did Bohr improve on Rutherford’s model?
He showed that electrons orbit the nucleus in fixed energy levels.
If chlorine-35 and chlorine-37 exist, which isotope is more abundant given chlorine’s average atomic mass ≈ 35.5 amu?
Chlorine-35
What happens to atomic stability when the balance of these forces is disrupted?
The atom becomes unstable and may undergo radioactive decay.
How can the period number on the periodic table help you draw a Bohr model?
It shows the number of energy levels the atom has.
Describe how electromagnetic and strong nuclear forces work together to keep an atom stable.
The electromagnetic force attracts negative electrons to the positive nucleus, while the strong nuclear force holds protons and neutrons together inside the nucleus despite repulsion.
Explain how Schrödinger’s quantum model changed our understanding of electron behavior.
It described electrons as existing in probability clouds (orbitals) rather than fixed paths.
Describe how to calculate an element’s average atomic mass from isotope data.
Multiply each isotope’s mass by its percent abundance (decimal form), then add the products.
Compare how electromagnetic and strong nuclear forces differ in range and strength.
The strong force acts only within the nucleus but is much stronger; the electromagnetic force acts over larger distances but is weaker.
When an electron transitions between energy levels, what determines the color of light produced?
The energy difference between the two energy levels — larger energy jumps produce higher-frequency (shorter wavelength) light, while smaller jumps produce lower-frequency (longer wavelength) light.