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Includes the following topics: A brief history of the atom including the work of Democritus, Aristotle, Al-Ghazali, Sennert, Lavoisier, Dalton,Thomson, Rutherford, Mikhailovskij, and Gross Atomic bookkeeping including protons, neutrons, electrons, valence electrons, average atomic mass, and nuclear stability Predicting chemical reactivity based on valence electrons.
Questions and Answers
1.
An atom is fundamentally different from an ion. This is because an ion...
A.
Never has an equal number of protons and electrons, and an atom always has an equal number of protons and electrons.
B.
Always has the same number of protons and neutrons; for atoms the number of protons may be different than the number of neutrons.
C.
Always has more electrons than protons; atoms always have the same number of protons as electrons.
D.
Never has more than 1.5 times as many neutrons as protons; atoms may be radioactive.
Correct Answer
A. Never has an equal number of protons and electrons, and an atom always has an equal number of protons and electrons.
Explanation atoms are uncharged: they always have an equal number of protons and electrons. An ion is by definition charged, meaning it always has an unequal number of protons and electrons.
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2.
Which statement about atoms A and B below is true?Atom A: 12 protons, 14 neutrons, 12 electronsAtom B: 13 protons, 14 neutrons, 12 electrons
A.
Atom A and B have the same mass number
B.
Atom A and atom B are different elements
C.
Atom A and Atom B have the same mass
D.
Both atom A and atom B are radioactive
Correct Answer
B. Atom A and atom B are different elements
Explanation Since atoms a and b have different numbers of protons, they are completely different elements: magnesium and aluminum
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3.
Aristotle proposed that the universe consists of four elements: __________
A.
Hydrogen, oxygen, nitrogen, and carbon (HONC)
B.
Hydrogen, oxygen, calcium, and a fourth element he simply called "metal"
C.
Unobtainium, element X, vibrainium, and adamantium
D.
Air, wind, earth, and fire
E.
Air, fire, earth, and water
Correct Answer
E. Air, fire, earth, and water
Explanation aristotles four elements were air fire earth and water.
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4.
Imagine that Rutherford discovered that during his gold foil experiment, ten percent of the alpha particles (helium cations) went through the gold foil in his team’s gold foil experiment and the rest were deflected at various angles (this is not what actually happened). Which model described below is consistent with this hypothetical result?
A.
The atom has a cubic shape with no space between atoms
B.
The atom is mostly empty space.
C.
Atoms are spherical and closely packed, with small amounts of space between atoms.
D.
Atoms are shaped like thin donuts, with very large spaces, or holes, inside each one.
Correct Answer
C. Atoms are spHerical and closely packed, with small amounts of space between atoms.
Explanation If only ten percent of the alpha particles passed through, a model is needed that is only ten percent space. The closely packed spheres fits the bill, whereas the large donut holes have too much space.
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5.
When the negative pole of a magnet is placed near a beam of electrons, the beam is deflected away from the magnet. This suggests that
A.
Electrons have no charge
B.
Electrons have a positive charge
C.
Electrons have a negative charge
D.
Electrons can have either a positive or negative charge depending on their magnetic field.
E.
Electrons have no mass
F.
Electons travel in curved paths and are therefore waves of energy, not matter.
Correct Answer
C. Electrons have a negative charge
Explanation Since opposite charges attract, this is strong evidence that electrons carry a negative charge
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6.
How many protons, neutrons, and electrons are in the following ion?
Correct Answer
D. 11 protons, 12 neutrons, ten electrons
Explanation sodium always has eleven protons; 12 neutrons are needed since the mass number is 23, and the positive charge means one electron has been lost.
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7.
Which atom is predicted to be radioactive?
A.
Na-23
B.
Au-196
C.
H-3
D.
Li-7
Correct Answer
C. H-3
Explanation Radioactive elements generally have more than 1.5 neutrons for each proton in the nucleus.
Na-23: 12/11
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8.
This is a true or false question.The two atoms described below are both isotopes of fluorine (F). atom A: Nine protons, ten neutrons, nine electronsatom B: Nine protons, nine neutrons, nine electrons
A.
True
B.
False
Correct Answer
A. True
Explanation Two atoms that vary only in the number of neutrons such as these are isotopes, in this case of fluorine
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9.
Magnesium has three of it's own isotopes. 78.7% is Magnesium-24. 10.13% is Magnesium-25. 11.17% is Magnesium-26.Calculate the average atomic mass of Magnesium, to one decimal place. Do not include units. For example, if you believe the answer is 24.1439 amu, simply enter 24.1
Correct Answer 24.3 24.4 24.2
Explanation (.787 x 24) + (.1013 x 25) + (.1117 x 26) = 24.3247
note that the best way to get a precise number is to enter it into your calculator as above with parentheses. This way all of the precision is carried to the final answer.
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10.
Imagine that Element A occurs naturally in the environment.Scientists have found 612 atoms of A-15, 829 atoms of A-16, and 244 atoms of A-17.Calculate the average atomic mass of the element A to two decimal places.Do not include units. For example if you believe the answer is 438.321466 amu, simply enter 438.32
Correct Answer 15.78 15.79 15.80 15.77
Explanation First, you have to get the percentages of all these isotopes of Element A. Add them all up together.
612+829+244 = 1685
Then, find the percentages of each - use the formula ([Number of Atoms/Total in the Sample] x 100)
([612/1685] x 100) = 36.320% of A-15.
([829/1685] x 100) = 49.1988% of A-16
([244/1685] x 100) = 14.4807% of A-17.
Now do what you've always done - multiply the abundances (move the percentages two places to the left) by the masses, add them all up
(.36320 x 15) + (491988 x 16) + (.144807 x 17) = 15.781527 = 15.78 amu
note that by entering the equation as above with parentheses the correct order of operations will be performed, and the precise numbers are carried along, leading to the most precise answer, which can then be rounded to two decimal places.
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11.
An atom of Pb-208 would have ? electrons.
A.
208
B.
82
C.
126
Correct Answer
B. 82
Explanation Atoms have equal numbers of protons and electrons (ions dont)
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12.
Silver has 2 isotopes.The first isotope has a mass of 106.905 amu (52%).The second isotope occurs in 48% abundance (48%).The atomic mass of silver is 107.868 amu.Which is closest to the mass of the second isotope? Please choose the closest answer.
Igor Mikhailovskij provided excellent evidence that atoms exist when he published __________.
A.
A genuine image of a molecule with visible bonds
B.
A genuine image of a neutron visible within a carbon atom, where the nucleus is shown in black and the neutrons within it visible as a blue region
C.
A genuine detailed image of an atom with a visible electron-rich region
D.
A genuine of two atoms of hydrogen bonded together wih visible electrons between them.
Correct Answer
C. A genuine detailed image of an atom with a visible electron-rich region
Explanation mikhailovskij was one of many who produced a detailed image of an atom. His was unique in that it showed electron orbitals (not neutrons) as a blue region within the atom
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14.
Over the last several years, genuine images of molecules have appeared in the scientific literature
A.
True
B.
False
Correct Answer
A. True
Explanation The statement suggests that genuine images of molecules have been published in scientific literature over the past few years. This implies that there is evidence to support the existence of these images and their inclusion in scientific research. Therefore, the answer "True" is correct as it aligns with the information provided in the statement.
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15.
Antoine Lavoisier demonstrated in the eighteenth century that the products of all chemical reactions have the same total mass as the reactants- this is now known as the law of conservation of mass. The key device he used to determine this was a(n) _______________
A.
Optical microscope
B.
Calorimeter
C.
Double pan balance
D.
Flame ionization spectrometer
E.
Primitive type of photography known as a daguerrotype
Correct Answer
C. Double pan balance
Explanation Lavoisier used a precise double pan balance to perform his experiments
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16.
Which ion has 50 electrons?
A.
Sn
B.
C.
D.
Correct Answer
B.
Explanation An atom of tin has 50 electrons, but it is not an ion. The antimony cation has 50 electrons and is an ion, not an atom.
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17.
What is the predicted chemical behavior of a nitrogen atom?
A.
A nitrogen atom is stable. it will neither lose nor gain electrons
B.
A nitrogen atom will gain three electrons
C.
A nitrogen atom will lose three electrons
D.
A nitrogen atom will gain six electrons to form three chemical bonds
E.
A nitrogen atom will gain one electron
Correct Answer
B. A nitrogen atom will gain three electrons
Explanation a nitrogen atom has seven electrons, with two in the first shell and five in the second. It is therefore unstable and it is easier for it to gain three electrons to obtain a full valence shell (the observed behavior of all atoms) rather than lose five. Note that it does not gain six electrons, although it does form three bonds.
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18.
The ion below has never been observed...Why? 2 protons, 2 neutrons, 3 electrons
A.
Helium is a noble gas with a full set of valence electrons and therefore will not form an ion.
B.
Helium is far more likely to lose an electron and form a cation, rather than gain an electron and form an anion as shown
C.
This ion is radioactive and would decompose so rapidly it cannot be observed
D.
This is not an ion, it is an atom
Correct Answer
A. Helium is a noble gas with a full set of valence electrons and therefore will not form an ion.
Explanation 2 protons defines this substance as helium which is a stable noble gas and will not ionize, becuase it has a full outer shell of electrons
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19.
Which of the following atoms or ions has six valence electrons
A.
Carbon
B.
The oxygen dianion, O2-
C.
Oxygen
D.
The carbon dication, C2+
Correct Answer
C. Oxygen
Explanation oxygen has six valence electrons: two in the first shell and six in the second.
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20.
19.9% of all Boron atoms are Boron-10. 80.1% of all boron atoms are Boron-11.Calculate the average atomic mass of Boron, to one decimal place. Please choose the closest answer.
A.
10.8 amu
B.
10.7 amu
C.
21.0 amu
D.
10.6 amu
E.
10.5 amu
Correct Answer
A. 10.8 amu
Explanation (.199 x 10) + (.801 x 11) = 10.801 amu
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21.
An atom is found to have ten protons and fourteen neutrons in the nucleus, and outside of the nucleus this atom contains ten electrons, with two electrons in the first shell and eight electrons in the second shell. Which statement best describes this atom?
A.
This atom is chemically stable, not radioactive, and is unlikely to form an anion or a cation
B.
This atom is chemically unstable, radioactive, and is likely to form an anion
C.
This atom is chemically unstable, not radioactive, and is likely to form a cation
D.
This atom is chemically unstable, not radioactive, and is likely to form an anion
E.
This atom is chemically stable, and is radioactvie
F.
This atom does not exist since none of the electrons are in the nucleus.
Correct Answer
A. This atom is chemically stable, not radioactive, and is unlikely to form an anion or a cation
Explanation This is Ne-20, a stable nonradioactive noble gas.
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22.
Why is beryllium likely to bond to oxygen?
A.
Because beryllium is likely to lose two electrons, and oxygen is likely to gain two electrons
B.
Because beryllium is likely to gain one electron and oxygen is likely to lose one electron
C.
Because beryllium is likelty to gain two electrons, and oxygen is likely to lose two electrons
D.
Because beryllium has four valence electrons and oxygen has 8 valence electrons
E.
Because beryllium oxide has no valence electrons
Correct Answer
A. Because beryllium is likely to lose two electrons, and oxygen is likely to gain two electrons
Explanation Beryllium is likely to bond to oxygen because beryllium tends to lose two electrons, while oxygen tends to gain two electrons. This allows both elements to achieve a stable electron configuration and form a bond.
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23.
Two atoms or ions are said to be isoelectronic when they have the same total number of electrons.Which two atoms or ions are isoelectronic?
A.
The sodium cation and magnesium
B.
The oxygen dianion and carbon
C.
Neon and argon
D.
The magnesium dication and neon
E.
Hydrogen and seaborgium
Correct Answer
D. The magnesium dication and neon
Explanation both the magnesium dication and neon have ten electons....they are isoelectronic
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24.
Which element has fourteen electrons in the third shell?
A.
Scandium, atomic number 21
B.
Iron, atomic number 26
C.
Lutetium, atomic number 71
D.
Silicon, atomic number 14
Correct Answer
B. Iron, atomic number 26
Explanation iron has two electrons in the first shell, eight in the second, fourteen in the third shell, and two in the fourth shell.
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25.
A zinc atom has eighteen electrons its third shell
A.
True
B.
False
Correct Answer
A. True
Explanation A zinc atom has two electrons in the first shell, eight in the second shell, eighteen in the third shell, and two in the fourth shell
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26.
A gold atom has sixteen valence electrons
A.
True
B.
False
Correct Answer
B. False
Explanation all of the transition metals (in the center block on the periodic table) have two valence electrons. In the case of gold, they are in the 6th shell.
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27.
Copper is made up of two isotopes, Cu-63 (62.9296 amu) and Cu-65 (64.9278 amu). Given copper's average atomic mass of 63.546 amu, what is the percent abundance of each isotope?Hint: let x be the abundance of the first isotope, and since they total 1, let 1-x be the abundance of the second isotope. Other methods can be used to answer this problems as well.Please choose the closest answer.
A.
69.15% Cu-63, and 30.85% Cu-65
B.
69.40% Cu-63, and 30.60% Cu-65
C.
68.20 % Cu-63, and 31.80% Cu-65
D.
31.80% Cu-63, and 68.20% Cu-65
Correct Answer
A. 69.15% Cu-63, and 30.85% Cu-65
Explanation Solution:
1) Write the following equation:
(62.9296) (x) + (64.9278) (1 - x) = 63.546
Once again, notice that 'x' and 'one minus x' add up to one.
2) Solve for x:
x = 0.6915 (the decimal abundance for Cu-63)
therefore the abundance of Cu-63 is 69.15%, and this leaves 30.85% for Cu-65. Plugging back in to the equation verifies that this is correct
(.6915)(62.9296) + (.3085)(64.9278) = 63.546
Having said all that, since this is a multiple choice question the easiest solution is simply to check each answer to see which one works!
(.6915)(62.9296) + (.3085)(64.9278) = 63.546 correct
(.6940)(62.9296) + (.3060)(64.9278) = 63.541 incorrect
(.6820)(62.9296) + (.3180)(64.9278) = 63.565 incorrect
(.3180)(62.9296) + (.6820)(64.9278) = 64.292 incorrect
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