Atom Test Period 8

1. 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

Atom A and B have the same mass number

Atom A and atom B are different elements

Atom A and Atom B have the same mass

Both atom A and atom B are radioactive

Since atoms a and b have different numbers of protons, they are completely different elements: magnesium and aluminum

Explanation

Since atoms a and b have different numbers of protons, they are completely different elements: magnesium and aluminum

2. Aristotle proposed that the universe consists of four elements: __________

Hydrogen, oxygen, nitrogen, and carbon (HONC)

Hydrogen, oxygen, calcium, and a fourth element he simply called "metal"

Unobtainium, element X, vibrainium, and adamantium

Air, wind, earth, and fire

Air, fire, earth, and water

aristotles four elements were air fire earth and water.

Explanation

aristotles four elements were air fire earth and water.

3. 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

(.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.

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.

Submit

4. 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

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.

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.

Submit

5. 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.

10.8 amu

10.7 amu

21.0 amu

10.6 amu

10.5 amu

(.199 x 10) + (.801 x 11) = 10.801 amu

Explanation

(.199 x 10) + (.801 x 11) = 10.801 amu

6. 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

Electrons have no charge

Electrons have a positive charge

Electrons have a negative charge

Electrons can have either a positive or negative charge depending on their magnetic field.

Electrons have no mass

Electons travel in curved paths and are therefore waves of energy, not matter.

Since opposite charges attract, this is strong evidence that electrons carry a negative charge

Explanation

Since opposite charges attract, this is strong evidence that electrons carry a negative charge

7. Over the last several years, genuine images of molecules have appeared in the scientific literature

True

False

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.

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.

8. 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) _______________

Optical microscope

Calorimeter

Double pan balance

Flame ionization spectrometer

Primitive type of photography known as a daguerrotype

Lavoisier used a precise double pan balance to perform his experiments

Explanation

Lavoisier used a precise double pan balance to perform his experiments

9. Why is beryllium likely to bond to oxygen?

Because beryllium is likely to lose two electrons, and oxygen is likely to gain two electrons

Because beryllium is likely to gain one electron and oxygen is likely to lose one electron

Because beryllium is likelty to gain two electrons, and oxygen is likely to lose two electrons

Because beryllium has four valence electrons and oxygen has 8 valence electrons

Because beryllium oxide has no valence electrons

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.

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.

10. A gold atom has sixteen valence electrons

True

False

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.

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.

11. How many protons, neutrons, and electrons are in the following ion?

begin mathsize 12px style Na to the power of plus minus 23 end style

Ten protons, eleven neutrons, twelve electrons

Eleven protons, twelve neutrons, thirteen electrons

12 protons, 11 neutrons, eleven electtons

11 protons, 12 neutrons, ten electrons

11 protons, 10 neutrons, 12 electrons

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.

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.

12. Which atom is predicted to be radioactive?

Na-23

Au-196

H-3

Li-7

Radioactive elements generally have more than 1.5 neutrons for each proton in the nucleus.
Na-23: 12/11 Au-170: 179/79 H-3: 2/1>1.5 RADIOACTIVE!
Li-7 4/3

Explanation

Radioactive elements generally have more than 1.5 neutrons for each proton in the nucleus.
Na-23: 12/11 Au-170: 179/79 H-3: 2/1>1.5 RADIOACTIVE!
Li-7 4/3

13. Which of the following atoms or ions has six valence electrons

Carbon

The oxygen dianion, O2-

Oxygen

The carbon dication, C2+

oxygen has six valence electrons: two in the first shell and six in the second.

Explanation

oxygen has six valence electrons: two in the first shell and six in the second.

14. 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?

This atom is chemically stable, not radioactive, and is unlikely to form an anion or a cation

This atom is chemically unstable, radioactive, and is likely to form an anion

This atom is chemically unstable, not radioactive, and is likely to form a cation

This atom is chemically unstable, not radioactive, and is likely to form an anion

This atom is chemically stable, and is radioactvie

This atom does not exist since none of the electrons are in the nucleus.

This is Ne-20, a stable nonradioactive noble gas.

Explanation

This is Ne-20, a stable nonradioactive noble gas.

15. Which element has fourteen electrons in the third shell?

Scandium, atomic number 21

Iron, atomic number 26

Lutetium, atomic number 71

Silicon, atomic number 14

iron has two electrons in the first shell, eight in the second, fourteen in the third shell, and two in the fourth shell.

Explanation

iron has two electrons in the first shell, eight in the second, fourteen in the third shell, and two in the fourth shell.

16. 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

True

False

Two atoms that vary only in the number of neutrons such as these are isotopes, in this case of fluorine

Explanation

Two atoms that vary only in the number of neutrons such as these are isotopes, in this case of fluorine

17. An atom of Pb-208 would have ? electrons.

208

82

126

Atoms have equal numbers of protons and electrons (ions dont)

Explanation

Atoms have equal numbers of protons and electrons (ions dont)

18. 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.

108.911 amu

108.684 amu

109.213 amu

108.524 amu

(.52)(106.905) + (.48)(x) = 107.868
55.5906 + 0.48x = 107.868
x 52.2774/0.48 = 108.91125 amu

Explanation

(.52)(106.905) + (.48)(x) = 107.868
55.5906 + 0.48x = 107.868
x 52.2774/0.48 = 108.91125 amu

19. The ion below has never been observed...Why? 2 protons, 2 neutrons, 3 electrons

Helium is a noble gas with a full set of valence electrons and therefore will not form an ion.

This ion is radioactive and would decompose so rapidly it cannot be observed

This is not an ion, it is an atom

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

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

20. A zinc atom has eighteen electrons its third shell

True

False

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

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

21. An atom is fundamentally different from an ion. This is because an ion...

Always has more electrons than protons; atoms always have the same number of protons as electrons.

Never has more than 1.5 times as many neutrons as protons; atoms may be radioactive.

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.

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.

22. 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?

The atom has a cubic shape with no space between atoms

The atom is mostly empty space.

Atoms are spherical and closely packed, with small amounts of space between atoms.

Atoms are shaped like thin donuts, with very large spaces, or holes, inside each one.

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.

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.

23. What is the predicted chemical behavior of a nitrogen atom?

A nitrogen atom is stable. it will neither lose nor gain electrons

A nitrogen atom will gain three electrons

A nitrogen atom will lose three electrons

A nitrogen atom will gain six electrons to form three chemical bonds

A nitrogen atom will gain one electron

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.

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.

24. 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?

The sodium cation and magnesium

The oxygen dianion and carbon

Neon and argon

The magnesium dication and neon

Hydrogen and seaborgium

both the magnesium dication and neon have ten electons....they are isoelectronic

Explanation

both the magnesium dication and neon have ten electons....they are isoelectronic

25. Which ion has 50 electrons?

Sn

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.

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.

26. Igor Mikhailovskij provided excellent evidence that atoms exist when he published __________.

A genuine image of a molecule with visible bonds

A genuine detailed image of an atom with a visible electron-rich region

A genuine of two atoms of hydrogen bonded together wih visible electrons between them.

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

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

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.

69.15% Cu-63, and 30.85% Cu-65

69.40% Cu-63, and 30.60% Cu-65

68.20 % Cu-63, and 31.80% Cu-65

31.80% Cu-63, and 68.20% Cu-65

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

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