Chemistry Exam 1
Which nuclear equations correctly describes beta emission?
234 234 Th ______>. Th + 0 -1e 90 91
If a neutral element has the following chemical notation, how many electrons does it have? carbon-13
6
How many alpha particles are emitted in the series of radioactive decay events from U-238 nucleus to a Pb-206 nucleus?
8
If a neutral element has the following chemical symbol, how many electrons does it have? 235 U 92
92
Germanium, Ge (number 32), computer chips operate faster than silicon, Si (number 14), computer chips. So how might a gallium, Ga, (number 31), chip compare with a germanium chip?
A gallium chip would be even faster because the gallium is more metallic.
The following statement describes which subatomic particle best? It is a nucleon.
A proton and a neutron
Which of the following does not describe a nuclear fission reaction? a. the number of nucleons in the products is different from the number of nucleons in the starting material b. The mass of the products is less than the mass of the reactants c. The energy released is proportional to the mass difference in the system d. All of the above e. none of the above
A.
Which of the following statements about fission is true? a. fission reactions have no critical-mass requirement. b. Fusion is easier than fission c. Fusion reactions can be easily controlled to make energy d. Fusion produces no harmful radiation e. None of the above
A. Fusion reactions have no critical-mass requirements
Which of the following statements about fusion is the most accurate? a. The mass of the products is less than the mass of the reactants b. The mass of the reactants is less than the mass of the products c. a nuclear fusion will always release energy d. overcoming the strong nuclear force results in the release of a large amount of energy e. fission releases more energy than fusion
A. The mass of the products is less than the mass of the reactants
Which of the following statements regarding a nucleon is true? a. attraction between nucleons changes their mass. b. The mass of a nucleon depends on which nucleus it is in. c. Some of the mass of a nucleon can be converted into energy by breaking certain nuclei d. Both A and C e. All of the above
All of the above
Which element would have chemical properties the most similar to chlorine (CI)?
Br
The element bromine (atomic number 35, Br, has two major isotopes of similar abundance, both around 50%. The atomic mass of bromine is reported in the periodic table as 79.904 atomic mass units. Choose the most likely set of mass numbers for these two bromine isotopes.
Br-79, Br-81
Why will nuclear fission probably not be used directly for powering automobiles? a. massive sheilding would be required to protect against radioactivity exposure b. radioactive wastes could not be adequately controlled c. It's more practical for cars to use the electricity generated by nuclear fission power plants. d. all of the above are true.
All of the above
People who work around radioactivity wear film badges to monitor the amount of radiation that reaches their bodies. These badges consist of small pieces of photographic film enclosed in a light-proof wrapper. What kind of radiation do these devices monitor?
Gamma radiation
How is it possible to deduce the identity of an element from its electron configuration?
If the atom is electrically neutral, the number of electrons corresponds to the atom's atomic number.
Where did the atoms that make up a newborn baby originate?
In the explosions of ancient stars
If you remove two protons and two neutrons from a gold atom (Au), what new element is formed (if any)?
Ir
A beam of protons and a beam of neutrons of the same energy are both harmful to living tissue. The beam of neutrons, however, is less harmful. Why?
Neutrons carry no electric charge and thus have a greater likelihood of passing through the tissue.
Is it at all possible for a hydrogen nucleus to emit an alpha particle?
No, because it does not contain enough nucleons
If all the molecules of a body remained part of that body, would the body have any odor?
No, because there would be no molecules traveling to our nose.
The age of the Dead Sea Scrolls was found by carbon-14 dating. Could this technique have worked if they were carved in stone tablets? Explain.
No, this method of dating requires a material that was once living.
Which of the following statements is true about Bohr's planetary model of the atom? a. the electrons actually orbit around the nucleus b. it is a physical model c. the energy difference between the orbits is continuous d. the electrons smoothly move from one orbit to the next. e. none of the above
None of the above
How many electrons are there in the third shell of sodium, Na (atomic number 11)?
One
How can a hydrogen atom, which has only one electron, have so many spectral lines?
One electron can be boosted to many different energy levels.
What evidence supports the contention that the strong nuclear force is stronger than the electrical interaction at short inter-nuclear distances?
Protons are able to exist side-by-side within at atomic nucleus.
Radium-226 is a common isotope on Earth, but has a half-life of about 1600 years. Given that Earth is some 5 billions years old, why is there any radium at all?
Radium-226 is a "daughter" isotope and the result of the radioactive decay of uranium.
Using the following generic atom description, choose the correct method for determining the number of neutrons. F X G
Subtract G from F
If an atom has 104 electrons, 157 neutrons, and 104 protons, what is it's approximate atomic mass?
The approximate atomic mass is 261
Does the average distance that a neutron travels through fissionable material before escaping increase or decrease when two pieces of fissionable material are assembled into one piece? Does this assembly increase or decrease the probability of an explosion?
The average distance increases while probability of an explosion also increases.
Why is the carbon-14 dating not accurate for estimating the age of materials more than 50,000 years old?
The concentration of carbon-14 in a body after 50,000 years.
A cat strolls across your backyard. An hour later, a dog with its nose to the ground follows the trail of the cat. Explain what is going on from a molecular point of view.
The dog is smelling molecules from the cat.
What is the relationship between the light emitted by an atom and the energies of the electrons in the atom?
The greater the frequency of a photon of light, the greater the energy packed into that photon.
A pair of protons in an atomic nucleus repel each other, but they are also attracted to each other. Why?
The pair attract each other by nuclear force but also repel one another by a weaker electrical force
What happens to the properties of elements across any period of the periodic table?
The properties of the elements gradually change across any period of the periodic table.
The shell model presented in this book is not very accurate. Why then is it presented?
The shell model is simpler and easy to understand
What do the electron configurations for all the group 18 noble gases have in common?
Their outermost occupied shells are filled to capacity.
Elements above uranium in the periodic table do not exist in any appreciable amounts in nature because they have short half-lives. Yet there are several elements below uranium in atomic number with equally short half-lives that do exist in appreciable amounts in nature. How can you account for this?
These isotopes result from the radioactive decay of uranium.
Which are older, the atoms in the body of an elderly person or those in the body of a baby?
They are of the same age, which is appreciably older than the solar system.
What property of an electron makes it possible to use electron microscopes?
They have shorter wavelengths than visible light.
Which of the following statements about radiation is true? a. Radiation can be a useful tool. Like fire, it is only dangerous when misused b. Radiation is new: It is a man-made phenomenon c. Radiation has no beneficial health applications All of the above Two of the above answers are reasonable
Two of the above answers are reasonable
Why would you expect alpha particles to be less able to penetrate materials than beta particles of the same kinetic energy?
Two of the above answers are reasonable.
Why can't we see atoms?
We see with light energy and the wavelength is larger than the object and so it is not reflected.
Just after an alpha particle leaves the nucleus, would you expect it to speed up? Why?
Yes. Once the alpha particle leaves the nucleus it accelerates because of mutual electric repulsion with the nucleus from which it escaped.
How would you describe light generated by heating pure elements if it was observed through a prism or spectroscope?
You would see a series of very sharp lines of emitted light.
Which of the following elements is the most stable from a nuclear point of view? a. iron b. hydrogen c. argon d. uranium e. all are equally stable
a
Which share is likely to need more material for a critical mass, a cube or a sphere? Why?
a cube because it has the greater surface area to volume ratio.
The following statement describes which subatomic particle best? It does not have an electrical charge.
a neutron
If a baseball were scaled up to the size of planet Earth, each of its atoms would be about the size of
a ping-pong ball
If three samples have the half-lives listed below, which is the most radioactive?
a sample with a half life of 20 mins
Which of the following best explains what is happening when an atom emits light?
An electron is dropping from a higher to a lower energy level with the difference in energy being the two being emitted as a light.
Why does plutonium not occur in appreciable amounts in natural ore deposits?
Any plutonium initially in the earths crust has long since delayed.
How is it possible for an element to decay "forward in the periodic table"-- that is, to decay to an element of higher atomic number?
As a beta particle is released, a neutron transforms into a proton.
You and your friend journey to the mountain foothills to get closer to nature and escape such things as radioactivity. While bathing in the warmth of a natural hot spring she wonders aloud how the spring get its heat. What do you tell her? You tell her that the hot water is the result of
radioactivity
Which of these is not a metal?
selenium (atomic no. = 34)
Which of the following provides the minimum amount of protection you need to block the following form of radiation? Alpha a. lead suit b. suntan lotion c. thick leather d. t shirt
suntan
Which chemical family is composed almost entirely of man-made elements?
the actinides
Coal contains only minute quantities of radioactive materials, yet there is more environmental radiation surrounding a coal-fired power plant than a fission power plant. This indicates that
the coal-fired power plant contains none of the radiation it releases
The atomic symbol represents
the name of the element,
Alpha and beta rays are deflected in opposite directions in a magnetic field because
they have opposite charges
The oldest known elements in the periodic table are the ones ________.
with odd looking atomic symbols.
What are some of the optimistic worldwide changes that may follow the advent of successful fusion reactors? a. economies will be geared to relative abundance rather than scarcity b. Humans will have more opportunities to focus on social issues, such as world hunger c. there will be fewer hostilities between nations d. All of the above
d. All of the above
The _______ represents the complete range of frequencies of light energy from radio waves to cosmic rays.
electromagnetic spectrum
How would you describe an isotope?
element with the same number of protons but a different number of neutrons
Radioactivity is a tendency for an element or a material to ______________.
emit radiation.
If you have to pick a diagram that represents the size of the atomic nucleus relative to the size of the atom, the diagram should be:
empty.
Where does the earth receive most of its energy?
external fusion
Which type of radiation from cosmic sources predominates on the inside of a high-flying commercial airplane: alpha, beta, or gamma?
gamma radiation
Elements that are in the same _________ gave a tendency to have very similar chemical properties due to periodic trends.
group
The alpha particle has twice the electric charge of the beta particle but deflects less than the beta in a magnetic field because it
has much more inertia
Which of the following is not the name of a chemical family?
heavy metals
Helium, He, is a nonmetallic gas and the second element in the periodic table. Rather than being placed adjacent to hydrogen, H, however, helium is placed on the far right of the table because
helium is most smilier to other group 18 elements.
A sample of radium is usually a little warmer than its surroundings because
its atoms are continually being struck by alpha and beta particles
Which of the following provides the minimum amount of protection you need to block the following form of radiation?
lead suit
One isotope for an element is distinguished from another isotope by the number of
neutrons
Light is emitted as an electron transitions from a higher energy state to a lower energy state. How long does it take for the actual transition to take place?
no time at all
An element is best described as a material
Consisting of only one type of atom
A certain radioactive element has a half-life of one hour. If you start with a 1-g sample of the element at noon, how much of this same element will be left at 3:00 PM?
0.125 gram
The isotope Cesium-137, which has a half-life of 30 years, is a product of nuclear power plants. How long will it take for this isotope to decay to about one-sixteenth its original amount?
120 years
If a neutral element has 8 neutrons and 7 electrons, which expression correctly identifies the element?
15 N 7
If an element has 9 protons and 10 neutrons and 9 electrons, what does it appear as?
19 F 9
If an element has 9 protons and 10 neutrons and 9 electrons, which expression correctly identifies the element?
19 F 9
Which of these does not describe a metal at room temperature? a. gas b. solid c. liquid d. shiny e. bendable
a. gas
Which of the following is a property of light? a. It is a wave b. It is a particle c. Its energy comes in packets of uniform size d. all of the above
all of the above
Which of the following statements about electrons is true? a. electrons have a negative charge b. electrons are particles c. electrons behave like waves d. electrons in atoms can be excited by light energy e. all of the above
all of the above
The following statement describes which subatomic particle best? It is located outside of the nucleus.
an electron
What does the following element description actually mean? 18 O 6
an oxygen atom with 6 protons and 12 neutrons
When 218/84 Po emits a beta particle, it transforms into a new element. What are the atomic number and atomic mass of this new element?
atomic number = 85; atomic mass = 218
When 226Ra decays by emitting an alpha particle, what is the atomic number of the resulting nucleus? What is the resulting atomic mass?
atomic number = 86; atomic mass= 222
In bombarding atomic nuclei with proton "bullets" the protons must be accelerated to high energies to make contact with the target nuclei
because the target nuclei are positively charged
You could swallow a capsule of germanium, Ge (atomic number 32), without significant ill effects. If a proton were added to each germanium nucleus, however, you would not want to swallow the capsule because the germanium would
become arsenic.
If two protons and two neutrons are removed from the nucleus of an oxygen atom, a nucleus of which element remains?
carbon-12
A neutron makes a better nuclear bullet than a proton or an electron because it
carries no electrical charge
Which of these properties describes a metal? a. conducts heat very well b. brittle c. fragile d. transparent
conducts heat very well