Chemistry - The Modern Atomic Theory
How does the electron-cloud model describe electrons?
An electron has a high probability of being in certain regions.
Electrons orbit the nucleus in specific, defined paths. Each path has a specified energy.
Bohr model
Identify each of the atomic models described here. Atoms are indivisible spheres.
Dalton model
Compare the modern (electron cloud) model of the atom with Dalton's atomic model. Which of these statements describe the two models correctly? Check all of the boxes that apply.
Dalton's model represented atoms as indivisible, but the modern theory recognizes that they contain smaller particles. The modern model explains all available data about atoms; Dalton's model does not.
Which equation was used by Albert Einstein to explain the photoelectric effect? [E = energy, h = Planck's constant, and v = frequency.]
E = hv
Which statement about Niels Bohr's atomic model is true? Higher orbits have lower energies. Each orbit has a specific energy level. Electrons can exist in any energy level. Orbits close to the nucleus have no energy.
Each orbit has a specific energy level.
According to the Bohr model of an atom, what happens when an electron moves from the second energy level to the third energy level and then back to the second energy level?
Energy is absorbed and then released to form an emission line.
Before Thomson's experiments, scientists accepted that the atom was made up of smaller particles. True or false?
False.
Thomson showed that the nucleus of an atom is small, dense, and positively charged. True or false?
False.
Describe the photoelectric effect and explain why it made modifications to the Rutherford model necessary.
Include: "According to the Rutherford model, light of any energy should be able to make electrons leave the atom and be emitted." Include "The energy of the emitted electrons should be related to the intensity of the light." Include: "Electrons are emitted only for certain wavelengths, and those wavelengths vary from atom to atom. The energy of the emitted electrons depends on the energy of the light, not its intensity."
Describe the main difference between the Bohr model and the electron cloud model of the atom
Include: "In the Bohr model, an electron's position is known precisely because it orbits the nucleus in a fixed path. Include: "In the electron cloud model, the electron's position cannot be known precisely. Only its probable location can be known."
Scientists made the following two observations about emission spectra: Each element has a unique emission spectrum. Atoms emit energy only at specific wavelengths. Describe how the Bohr model explains both of these observations.
Include: "In the Bohr model, electrons can exist only in certain energy levels surrounding the atom." Include: "When electrons jump from a higher energy level to a lower one, they emit light at a wavelength that corresponds to the energy difference between the levels." Include: "The energy levels in each atom are unique."
Describe the main difference between the Bohr model of the atom and the Rutherford model.
Include: "In the Rutherford model, electrons can exist in any location outside the nucleus." Include: "In the Bohr model, electrons can exist only in certain energy levels surrounding the atom."
Which statement about the electron-cloud model is true?
It is the currently accepted atomic model.
A hydrogen electron is elevated from level 1 to level 2. Another electron is elevated from level 2 to level 4. The transition requiring the greatest energy change is
Level 2 to level 4
Light is emitted by electrons when they drop from one energy level to a lower level. Which transition results in the emission of light with the greatest energy?
Level 4 to level 2
After Thomson's, Millikan's, and Rutherford's experiments, scientists generally accepted that an atom contains a small, positively charged nucleus surrounded by negatively charged electrons. True or false?
True.
Millikan's experimental results allowed him to determine the charge of the electron. True or false?
True.
Rutherford showed that most of the atom's volume is empty space. True or False?
True.
The modern-day quantum model of the atom is better than John Dalton's model because it
answers many questions about atoms.
In an experiment, shining which type of light on a strip of metal would be least likely to produce the photoelectric effect?
bright red light
An electron's position cannot be known precisely. Only its probability of being in a certain location can be known.
electron cloud model
Natalie observes these characteristics in the model of an atom. 1) Includes positive charge 2) Contains electrons 3) explains the photoelectric effect 4) suggests the probable locations of electrons Which model is Natalie most likely examining?
electron-cloud model
Which atomic model states that it is impossible to know the exact location of electrons around the nucleus?
electron-cloud model
A change in which property of light will have no effect on whether or not the photoelectric effect occurs?
intensity
Electrons are embedded in a mass of positively charged matter.
plum pudding model
Blue light waves have more energy than red light waves. Which of these situations most likely produces a photoelectric effect? You may assume that the same metal is used in each situation. Check all that apply.
shining dim blue light on a strip of metal, and shining bright blue light on a strip of metal
