A
Who proposed the nuclear model of the atom?
Ernest Rutherford
What is the charge of a proton?
Positive (+1)
What holds electrons in orbit around the nucleus?
Electrostatic attraction between negative electrons and positive protons
What does “purity” mean in science?
It describes how much of a specific substance is in a sample without impurities.
True or False: All chemical reactions produce only pure products.
False
Why might a reaction produce more than one product?
Because of side reactions or incomplete reactions.
What experiment led Rutherford to propose his atomic model?
Gold foil experiment (alpha particle scattering)
What is the charge of a neutron?
Neutral (0 charge)
Why are positive and negative charges attracted to each other?
Opposite charges attract due to electrostatic forces.
What is the percentage purity if 80g of sugar is obtained from a 100g impure sample?
80%
Give one reason why determining purity is important in medicine.
To ensure safety and effectiveness of the medicine.
Name one real-life example of an impure product from a reaction.
Crude oil, unrefined sugar, or raw metal ores.
According to Rutherford, where are most of the atom’s mass and positive charge located?
In the small, dense nucleus at the center of the atom
Which subatomic particle is responsible for chemical bonding?
Electrons
What is the name for the force between positive protons and negative electrons?
Electrostatic force
Describe how electrostatic attraction keeps an atom stable.
It pulls electrons toward the nucleus, balancing their motion away.
A student separates 25g of copper from 120g of ore. Calculate the percentage purity.
(25 ÷ 120) × 100 = 20.8%
A reaction produces a desired product and a byproduct. Explain why purification is needed.
To remove impurities and make the product usable or safe.
Explain why most alpha particles passed straight through the gold foil in Rutherford’s experiment.
Because most of the atom is empty space
Why do atoms have no overall electrical charge?
Because the number of protons equals the number of electrons
Predict what would happen if an atom gained an extra electron. What would its charge become?
It would become a negative ion (anion).
Explain why removing an electron from an atom requires energy.
Energy is needed to overcome the electrostatic attraction to the nucleus.
Suggest one method a chemist might use to increase the purity of a substance.
Distillation, crystallization, or chromatography.
Analyze: Why is it almost impossible to achieve 100% purity in industrial chemical processes?
Due to unavoidable impurities and practical limitations in separation methods.
Compare Rutherford’s model to Thomson’s Plum Pudding model. What major difference did Rutherford propose?
Rutherford said positive charge is concentrated in a nucleus, not spread out.