Physics practice exam unit 8
What is the total number of protons and neutrons in a water molecule?
18
How many electrons are unpaired in the outermost shell of sulfur (S, atomic number 16)?
2
How many protons should be added to the nuclei of oxygen atoms so the resulting gas will glow red when an electric current flows through it?
2
The nucleus of an electrically neutral iron atom contains 26 protons. How many electrons does this iron atom have?
26
How many electrons are unpaired in the outermost shell of aluminum (Al, atomic number 13)?
3
Balance these equations: ____ H with subscript((2)) (g) + ____ N with subscript((2)) (g) rightarrow ____ NH with subscript((3)) (g)
3, 1, 2
How many electrons are in the outermost shell of strontium (Sr, atomic number 38)?
4
Which set of coefficients balance the following chemical equation? ____ Al + ____ O2 rightarrow ____ Al2O3
4, 3, 2
How many electrons are in the outermost shell of phosphorus (P, atomic number 15)?
5
How many shells are occupied by electrons in the gold atom (Au, atomic #79)?
6
When radium (A = 88) emits an alpha particle, the resulting nucleus has atomic number
86
The following three boxes represent the number of submicroscopic particles within a given volume of a particular substance at different temperatures. Which box represents the greatest density? Which box represents the greatest temperature?
A and C
How might the spectrum of an atom appear if its electrons were not restricted to particular energy levels?
A broad spectrum of all colors would be observed.
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.
Why is it not possible for the STM to make images of the inside of an atom?
All of the above are reasonable answers.
What are the three types of rays produced in radioactive decay? Which will penetrate farther into material?
Alpha rays, beta rays, and gamma rays: Alpha rays are streams of particles, which are the nuclei of helium atoms. They are the heaviest particles ejected by radioactive materials, and are positively charged. Beta rays are streams of electrons, emanating from the nucleus, and are negatively charged. Gamma rays are high-frequency electromagnetic waves ejected by the atomic nucleus during decay. Gamma rays have no electric charge and are the most penetrating of the rays.
Humidity is a measure of the amount of water vapor in the atmosphere. Why is humidity always very low inside your kitchen freezer?
At the cold temperatures of your kitchen freezer, water molecules in the vapor phase are moving relatively slowly, which makes it easier for them to stick to inner surfaces within the freezer or to other water molecules.
The element bromine, Br (atomic number 35), 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
Which of the following diagrams best represents the size of the atomic nucleus relative to the size of the atom:
D
How might you distinguish a sodium-vapor street lamp from a mercury-vapor street lamp?
Look at the street lamps through a spectroscope and match their spectral patterns to their respective atomic spectra.
What are some physical and chemical properties of the element Rubidium (Rb, atomic #37)?
Rubidium is a soft metal that reacts with water, much like all other elements of group 1, such as sodium.
Some politicians take pride in maintaining a particular point of view. They think that a change of mind would be seen as a sign of weakness. How is a change of mind viewed differently in science?
Science deals with facts that are confirmed by experiments. A "change of mind" in science, therefore, is usually the result of new experimental evidence obtained from experiments.
If you eat metallic sodium or inhale chlorine gas, you stand a strong chance of dying. Let these two elements react with each other, however, and you can safely sprinkle the compound on your popcorn for better taste. What is going on?
Sodium chloride has nothing in common with sodium and chlorine.
About how old are the atoms that make up the body of an 18-year-old student?
The age of most of the atoms that make up our bodies and the world around us are as old as the universe itself. Atoms heavier than hydrogen were manufactured in stars, and those heavier than iron were made as giant stars exploded. The atoms that make up our bodies were once the material of stars that have long since exploded.
Why are the atomic masses listed in the periodic table not whole numbers?
The atomic masses are average atomic masses.
How does an electron get from one lobe of a p orbital to the other?
The electron actually exists in both lobes at the same time.
Evidence for the existence of neutrons did not come until many years after the discoveries of the electron and the proton. Give a possible explanation.
The neutron lacks an electrical charge.
Why should the periodic table not be memorized?
The periodic table is to a chemist as a dictionary is to a writer. It is reference that should always be available. Like the dictionary, the periodic table is to be used, not memorized.
Why is the process of science not restricted to any one particular method?
The scientist needs to be open to all possibilities and different ways of doing science in order to gain as much knowledge as possible from his or her research.
Why doesn't the uranium ore in mines spontaneously explode?
The uranium ore is primarily the isotope U-238, which doesn't fission. U-235 atoms in the ore are too far apart for a chain reaction.
A radioisotope placed near a radiation detector registers 80 counts per second. Eight hours later the detector registers 5 counts per second. What is the half-life of the radioisotope?
Two hours: Since 80 halved 4 times is 5, there have been four half-life periods in the 8 h, and 8 h/4 = 2 h.
Does an orbital or a shell of orbitals have to contain electrons in order to exist?
Two of the above are reasonable answers.
Which is the smallest particle listed below?
a quark
The function of graphite in the first atomic reactor was to
absorb fast neutrons.
Fissioning an iron nucleus yields a net
absorption of energy.
Fusing two iron nuclei yields a net
absorption of energy.
Both nitrogen and phosphorus are able to attract three more electrons to their outer shells because
all of the above.
A molecule has
all of these
The air in this room has
all of these
The half-life of a radioactive substance is independent of
all of these
Which experiences the greatest electrical force in an electric field?
alpha particle
Nuclei of atoms that make up a newborn baby were made in
ancient stars.
When uranium-238 absorbs a neutron, it
becomes a beta emitter.
If a pair of helium nuclei are fused together, the result is
beryllium.
Of the three sciencesÑphysics, chemistry, and biologyÑthe most complex is
biology because it is based upon both the laws of chemistry and physics.
Although the nucleus of a carbon atom has a charge of +6, the charge experienced by carbon's valence electrons is different because
both A and B
In which lobe of a p orbital is an electron most likely found?
both lobes
In which of these processes is an element of matter changed into a completely different element?
both of these
If two protons are removed from an oxygen nucleus, the result is
carbon.
When a nucleus emits a beta particle, its atomic number
changes, but its mass number remains constant.
A chemical mixture is distinguished from a chemical compound in that
chemical compounds may be found in a chemical mixture.
Energy released by the Sun results from the process wherein atomic nuclei
combine
The operation of a cloud chamber relies on
condensation.
Another interesting periodic trend is the density of the elements. We find that osmium, Os (atomic number 76) has the greatest density of all elements, and, with some exceptions, the closer an element is positioned to osmium, the greater its density. Based upon this trend, list the following elements in order of increasing density: copper, Cu, gold, Au, platinum, Pt, and silver, Ag.
copper, Cu < silver, Ag < gold, Au < platinum, Pt
The origin of cosmic rays is the
cosmos.
The most harmful radiations are those that
damage living cells
The volume of matter comes mostly from its
electrons
The number of elements in a period is
equal to the electron capacity of the shells.
An electron de-excites from the fourth quantum level to the third and then directly to the first. Two frequencies of light are emitted. How do their combined energies compare to the energy of the single frequency that would be emitted by de-excitation from the fourth level directly to the first level? Answer: The combined energies of the two frequencies emitted by the one electron is
equal to the energy of the single frequency
Which experiences the least electrical force in an electric field?
gamma ray
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 similar to other group 18 elements.
Detonation of a fusion type hydrogen bomb is started by
igniting a small fission bomb.
Strontium, Sr (number 38), is especially dangerous to humans because it tends to accumulate in calcium-dependent bone marrow tissues (calcium, Ca, number 20). This fact relates to the organization of the periodic table in that strontium and calcium are both
in group 2 of the periodic table.
In both fission and fusion, mass
is changed to the form of kinetic energy.
When two light atoms fuse together, mass
is converted to kinetic energy of neutrons.
Compared to the sum of the masses of all the individual nucleons in their separate states that make up a nucleus, the mass of the composite nucleus is
less
As atoms get more massive they become smaller in size because
more mass means more protons, which act to pull electrons in closer to the nucleus.
The reason a granite block is mostly empty space is because the atoms in the granite are
mostly empty space themselves.
To change mercury into gold, a pair of protons must be
neither of these
When a gamma ray is emitted by a nucleus, the nucleus then has appreciably less
neither of these
Which of the following are electrically neutral?
neutron
Light is emitted as an electron transitions from a higher energy orbital to a lower energy orbital. How long does it take for the actual transition to take place?
no time at all
The phase in which atoms and molecules no longer move is the
none of the above
When thorium (A = 90 ) emits a beta particle, the resulting nucleus has atomic number
none of these
Solid matter is mostly empty space. The reason solids don't fall through one another is because
of electrical forces.
In bubble chambers, charged particles move in spirals because
of energy dissipation.
During a chemical reaction
old atoms stick around merely switching partners.
In an electrically neutral atom, the number of protons in the nucleus is balanced by an equal number of
orbital electrons.
Detonation of a fission type atomic bomb is started by
pressing together several small pieces of uranium.
The weight of matter comes mostly from its
protons
Brownian motion has to do with the
random motions of atoms and molecules.
Artificially induced radioactive elements generally have
short half lives
Assuming all the atoms exhaled by Julius Caesar in his last dying breath are still in the atmosphere, then we probably breathe one of those atoms with each
single breath.
Suppose that a certain atom possesses only four distinct energy levels. Assuming that all transitions between levels are possible, how many spectral lines will this atom exhibit?
six
An element emits 1 alpha particle, 1 positron, and 3 beta particles. Its atomic number
stays the same.
If we doubled the magnifying power of the most powerful optical microscope in the world, we would
still not be able to see an atom.
About how many elements do you have access to as a consumer of market goods?
ten
The difference in the mass of a nucleon when outside an atomic nucleus compared to inside the nucleus depends on
the atomic number of the nucleus.
The alkali metals (group 1) tend to form 1+ ions while the alkali-earth metals (group 2) tend to form 2+ ions because
the charges of these ions corresponds to the number of valence electrons that may be lost.
What makes an element distinct?
the number of protons
The purpose of coefficients in chemical equations is to make
the number of times each element appears as a reactant and as a product the same.
Suppose a hydrogen bomb were exploded in a box that could contain all the energy released by the explosion. Compared to the weight of the box before the explosion, the weight of the box after the explosion would be
the same
There are about as many atoms of air in our lungs at any moment as there are breaths of air in the atmosphere of
the whole world.
It's impossible for a hydrogen atom to emit an alpha particle.
true
Pure elements can be transformed into entirely different elements. This statement at the present time is
true
How many different elements are in a water molecule?
two
Which will leak more neutrons, two separate lumps of uranium or the same two lumps stuck together?
two separate lumps
In a breeder reactor
uranium is converted into plutonium.
Some of the older known elements are the ones
whose atomic symbols and modern name don't match.
Does a 2-kg solid iron brick on Earth have twice as much mass as a 1-kg solid iron brick at the same place on Earth? Twice as much weight? Twice as much volume?
yes, maybe, and yes
