Which particle carries positive electric charge?
- Neutron
- Proton
- Electron
Answer and explanation
Proton
A proton's charge is positive; a neutron is neutral.
Subjects
Atomic & nuclear models
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Sample exercises
A neutral atom has 7 protons. How many electrons does it have?
Answer and explanation
7
Neutrality requires equal numbers of positive proton and negative electron charges.
For photons, doubling frequency does what to energy per photon?
- Leaves it unchanged
- Doubles it
- Halves it
Answer and explanation
Doubles it
E = hf is directly proportional to frequency.
An atomic transition releases 3 units of energy per photon. How much energy is carried by 4 such photons in the same units?
Answer and explanation
12
4 × 3 = 12 in the stated energy units.
Why should an electron-orbit sketch not be treated as a fully literal description?
Answer and explanation
It is a simplified representation; electron states are not generally classical planetary paths.
Credit model purpose and limitation without demanding advanced formalism.
What process can occur when an atom absorbs a photon of a suitable energy?
- Its number of protons must double
- A transition to a higher energy state
- Its nucleus must become a planet
Answer and explanation
A transition to a higher energy state
A matching energy can excite the atom within the model.
Study notes
Atomic models and photon energy
Distinguish nuclei, electron energy levels and the scope of simple models.
Grades 10–12Atomic models and photon energy · Revision sheet
Distinguish nuclei, electron energy levels and the scope of simple models.
Grades 10–12Half-life: a statistical model
Apply repeated halving without predicting an individual decay time.
Grades 9–12Half-life: a statistical model · Revision sheet
Apply repeated halving without predicting an individual decay time.
Grades 9–12Expected amount after half-lives
This predicts the expected remaining amount for a large ensemble; individual decays are random.
Grades 9–12Photon energy in a scaled unit
Track powers of ten; the answer is a coefficient in units of 10⁻¹⁹ J.
Grades 11–12Atomic & nuclear models · Formula reference
Formula reference
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