Developing the Model of the Atom Flashcards
Atomic Structure (17 cards)
Who proposed that matter was made up of indivisible spheres called ‘atoms’?
John Dalton
Dalton’s theory was influenced by Democritus’ ideas.
What did J. J. Thomson discover that led to the modification of Dalton’s theory?
Electrons
This discovery indicated that atoms could be broken down into smaller particles.
What is the name of the model Thomson proposed?
Plum pudding model
In this model, atoms were thought to be positive spheres with negative electrons embedded.
What experiment did Rutherford’s lab conduct in 1909?
Alpha scattering experiment
They fired alpha particles at a thin gold foil.
What did the alpha scattering experiment reveal about the atom?
Most of the mass is concentrated in a tiny nucleus
This contradicted the plum pudding model.
What did the deflection of alpha particles indicate about the nucleus?
It must have a positive charge
This is because it repelled the positively charged alpha particles.
What is the first nuclear model of the atom characterized by?
A positively charged nucleus surrounded by a cloud of negative electrons
This model emerged from Rutherford’s findings.
Who proposed that electrons orbit the nucleus at specific distances called energy levels?
Niels Bohr
Bohr’s model included quantized energy levels for electrons.
What did James Chadwick discover in 1932?
The neutron
This discovery explained the imbalance between atomic and mass numbers.
What particles are found in the nucleus of an atom?
Protons and neutrons
Protons have a positive charge, while neutrons are neutral.
What is the relative charge of a proton?
+1
Protons contribute to the positive charge of the nucleus.
What is the relative charge of an electron?
-1
Electrons balance the charge of protons in the atom.
What happens to electrons when they gain energy?
They move to a higher energy level
This often occurs when they absorb electromagnetic radiation.
What occurs when an electron releases energy?
It moves to a lower energy level
This brings it closer to the nucleus.
What is formed when one or more outer electrons leave an atom?
A positively charged ion
The loss of negative charge leads to a net positive charge.
What is the approximate size of an atom’s radius?
1 x 10^-10 m
This is much larger than the nucleus, which is about 10,000 times smaller.
True or False: The current atomic model is unlikely to change in the future.
False
Scientific understanding can evolve with new experiments.
