PHS 112
Test 4 Review
Chapters 12-15
Which are older, the atoms in the body of an elderly person or those in the body of a baby?
Same age. All atoms on earth date back billions of years to the big bang and fusion in the stars since then.
Does it make sense to say that a textbook is about 99.9 percent empty space?
The actual size of the protons, neutrons, and electrons is very small compared to the size of an atom. The
protons and neutrons are in the very small nucleus. Most of the space in an atom is occupied by the
electrons. They are not very big, but “fill” the space by moving very rapidly.
39
How many protons and how many neutrons does an atom of 31 Ga have? Which number in the gallium symbol is the mass number? Where are the
protons and neutrons located?
Based in the atomic number, 31, there are 31 protons. The difference between the mass number, 39, and the
atomic number indicates there are 8 neutrons. All protons and neutrons are in the nucleus. (This number of
neutrons is very low. The mass number was supposed to be 69 meaning a real gallium atom would have 38
neutrons.)
40
36
Using a periodic table, determine what element has 18 protons and 22 neutrons. 18𝐴𝑟 What element has 2 fewer protons and 2 fewer neutrons? 16𝑆
Which of the three subatomic particles are heavy? protons and neutrons
Where are the metals located on the periodic table? The metalloids?
Most of the elements are metals and are located on the left side of the periodic table. The metalloids are the
elements along the zig-zag line between the metals and the nonmetals.
What element is oldest? Hydrogen Where did the other elements come from? They were formed by the fusion of hydrogen
atoms that occurred inside of stars.
Name an element with properties much like Neon. The elements in a group have similar properties. He, Ar, Kr, . . .
What period is the element phosphorus (P) located in. Period 3. Third row from the top.
What is the difference between a conceptual model and a physical model?
A physical model represents something that can be seen. Usually it is scaled up or down to be a more
convenient size to view. (ex. A globe to represent the earth.) A conceptual model describes what
something that cannot be seen. As our understanding (concept) changes, the model will look different.
What is a photon?
A particle of energy. Usually related to electromagnetic radiation.
In the planetary model of the atom, the electrons (particles) circle the nucleus at specific distances corresponding to energy levels. Who came up
with this model? Bohr
What color of visible light has the highest energy? Violet. Photons of violet light have more energy than other colors.
What do the structures of all atoms in a group have in common? They each have the same number of valence electrons.
Answer the following for alpha, beta, and gamma particles.
Alpha Which is most penetrating? Gamma Which is an electron? Beta Which
Alpha
What do the letters stand for in the “rad” radiation measurement? Radiation Absorbed Dose
How much of a 32 gram sample of radioactive material will remain after 1 half-life? 16 grams
3 half-lifes? 4 grams
What is the name of the force that holds the nucleus together? strong nuclear force
If an atom has 104 electrons, 157 neutrons, and 104 protons, what is its approximate atomic mass? 157 + 104 = 261 If this atom loses and
alpha particle, how many protons and neutrons would it have left? 102 protons, 155 neutrons
206
206
If 81 Tl becomes 82 Pb , what type of radiation is released?
Mass stayed the same when the atomic number increased by one. Beta radiation.
Which has no charge?
Gamma
Which is heaviest?
causes more damage when it hits a living cell?
The half-life of carbon-14 is 5,730 years. A sample is found to have one-eighth the original amount of carbon-14 in it. How old is the sample?
D) 17,200 years
After 1 half-life, one-half of a radioactive substance remains. After 2 half-lifes, one-quarter of the substance
remains. After 3 half-lifes one-eighth of the substance remains. After 4 half-lifes one-sixteenth of the
substance remains. (and on, and on) So if “one-eighth the original amount of carbon-14” remains, it has been
3 half-lifes. 3 x 5,730 years = 17,190 years
Which of the following statements about fission is true?
A) The amount of energy released in the fission of large nuclei is very large.
If a fusion reaction produces no appreciable radioactive isotopes, why does a hydrogen bomb produce significant radioactive fallout?
C) The radioactive fallout is a result of the fission reaction used to ignite the
thermonuclear fusion reaction.
The nuclear fusion occurring in stars produces all the elements heavier than hydrogen.
How can we tell whether the figure at right represents a chemical reaction?
The atoms have regrouped (connected differently). The left box has gray atoms paired and black atoms
paired. The right box has gray atoms paired with white atoms.
Which of the following would not be considered a physical property? A) temperature at which a material catches on fire
Fire is a chemical reaction. This temperature refers to that reaction (chemical property).
How many atoms are in one molecule of Na2SO4? 2 Na atoms + 1 S atom + 4 O atoms= 7 atoms
How many different elements are in the compound C6H12O6? Carbon, hydrogen, and oxygen. 3 elements
Define ionic bonding. The attraction between ions that have opposite charges.
Draw the electron dot symbol for a nitrogen atom. N
Most atoms lose, gain, or share electrons until there are 8 (#) electrons in their valence shell? What is the valence shell?
The highest energy shell that has electrons in it. The outermost shell.
True When excited (by heat or electricity) atoms of an element give off specific colors of light.
True Light behaves as both a wave and a particle. Electrons do too.
True Unstable nuclei can break apart forming atoms of different elements.
What is the formation of a deferent element called? transmutation
True Medical doses of radiation are measured in rem. It is related to the amount of damage the radiation will cause.
True Fission is a chain reaction. Fusion is not a chain reaction.
True Uranium-235 used in nuclear weapons is not very radioactive (has a long half-life).
Different sources report different numbers for the half-life of U-235. A web search suggests it is more than
700 million years.
True The nucleons are lightest in iron nuclei. See the Figure 13.30 on page 339.
True Hydrogen is very abundant on the earth. Mostly in water.
True Applied research tries to use information to do/make something useful.
Basic research tries to make new discoveries but does not have a specific use in mind.
True The figure, above-right, shows the submicroscopic particles of a substance going from the liquid state to the gas state.
False Because water contains oxygen atoms, the properties of water and oxygen are the same.