Chapter 2

25 July 2022
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question
About twenty-five of the ninety-two natural elements are known to be essential to life. Which four of these twenty-five elements make up approximately 96 percent of living matter?
answer
carbon, hydrogen, nitrogen, oxygen.
question
Trace elements are those required by an organism in only minute quantities. Which of the following is a trace element that is required by humans and other vertebrates, but not by other organisms such as bacteria or plants?
answer
iodine.
question
Which of the following statements is FALSE?
answer
All life requires the same essential elements.
question
Which of the following are compounds?
answer
H2O and CH4, but not O2.
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Knowing the atomic mass of an element allows inferences about which of the following?
answer
the number of protons plus neutrons in the element.
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In what way are elements in the same column of the periodic table the same? They have the same number of _____.
answer
electrons in their valence shells when neutral.
question
Molybdenum has an atomic number of 42. Several common isotopes exist, with mass numbers from 92-100. Therefore, which of the following can be true?
answer
Molybdenum atoms can have between 50 and 58 neutrons.
question
Carbon-12 is the most common isotope of carbon and has a mass number of 12. However, the average atomic mass of carbon found on a periodic table is slightly more than 12 daltons. Why?
answer
Some carbon atoms in nature have more neutrons.
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Which of the following best describes the relationship between the atoms described below?
answer
They are isotopes.
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The atomic number of nitrogen is 7. Nitrogen-15 has a greater mass number than nitrogen-14 because the atomic nucleus of nitrogen-15 contains _____.
answer
8 neutrons.
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From its atomic number of 15, it is possible to predict that the phosphorus atom has _____.
answer
15 protons and 15 electrons.
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Fluorine has an atomic number of 9. Which of the following would you do to a neutral fluorine atom to complete its valence shell?
answer
add 1 electron.
question
Magnesium has an atomic number of 12. What is the most stable charge for a magnesium ion?
answer
a +2 charge.
question
Refer to the figure above (first three rows of the periodic table). What element has properties most similar to carbon?
Refer to the figure above (first three rows of the periodic table). What element has properties most similar to carbon?
answer
silicon.
question
How many neutrons are present in the nucleus of a phosphorus-32 (32P) atom (see the figure above)?
answer
17.
question
How many electrons will a single atom of sulfur with no charge and no bonds have in its valence shell (see the figure above)?
answer
6.
question
Based on electron configuration, which of the elements in the figure above would exhibit a chemical behavior most like that of oxygen?
answer
sulfur.
question
Which one of the atoms shown would be most likely to form a cation with a charge of +1?
Which one of the atoms shown would be most likely to form a cation with a charge of +1?
answer
A.
question
Which one of the atoms shown would be most likely to form an anion with a charge of -1?
Which one of the atoms shown would be most likely to form an anion with a charge of -1?
answer
D.
question
Oxygen has an atomic number of 8 and most commonly, a mass number of 16. Thus, what is the atomic mass of an oxygen atom?
answer
approximately 16 daltons.
question
If you change the number of neutrons in an atom, you create _____.
answer
an isotope.
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Can the atomic mass of an element vary?
answer
Yes. Adding or losing neutrons will change the atomic mass without forming a different element.
question
Which of the following is the best description of an atom's physical structure?
answer
Atoms are little bubbles of space with mass concentrated at the center of the bubble.
question
A salamander relies on hydrogen bonding to stick to various surfaces. Therefore, a salamander would have the greatest difficulty clinging to a _____.
answer
surface of hydrocarbons.
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A covalent chemical bond is one in which _____.
answer
outer-shell electrons of two atoms are shared so as to satisfactorily fill their respective orbitals.
question
What is the maximum number of covalent bonds that an oxygen atom with atomic number 8 can make with hydrogen?
answer
2.
question
Nitrogen (N) is more electronegative than hydrogen (H). Which of the following is a correct statement about the atoms in ammonia (NH3)?
answer
Each hydrogen atom has a partial positive charge; the nitrogen atom has a partial negative charge.
question
Bonds between two atoms that are equally electronegative are _____.
answer
nonpolar covalent bonds.
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What results from an unequal sharing of electrons between atoms?
answer
a polar covalent bond.
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A covalent bond is likely to be polar when _____.
answer
one of the atoms sharing electrons is more electronegative than the other atom.
question
What is the difference between covalent bonds and ionic bonds?
answer
Covalent bonds involve the sharing of electrons between atoms; ionic bonds involve the electrical attraction between charged atoms.
question
The atomic number of chlorine is 17. The atomic number of magnesium is 12. What is the formula for magnesium chloride?
answer
MgCl2.
question
How many electron pairs are shared between carbon atoms in a molecule that has the formula C2H4?
answer
2.
question
Which bond or interaction would be difficult to disrupt when compounds are put into water?
answer
covalent bonds between carbon atoms.
question
Water molecules are attracted to one another by _____.
answer
hydrogen bonds.
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Van der Waals interactions may result when _____.
answer
electrons are not symmetrically distributed in a molecule.
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What is the maximum number of hydrogen atoms that can be covalently bonded in a molecule containing two carbon atoms?
answer
6.
question
What results from the chemical reaction illustrated above? The reactants have no charge.
answer
a cation with a net charge of +1 and an anion with a net charge of -1. Sorry I couldn't find a picture and I can't upload one because I don't have premium.
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What is the atomic number of the cation formed in the reaction illustrated above?
answer
11.
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What causes the shape of the molecule shown above?
answer
the shape of the sp3 hybrid orbitals of the electrons shared between the carbon and hydrogen atoms.
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How many electrons are involved in a single covalent bond?
answer
2.
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How many electrons are involved in a double covalent bond?
answer
4.
question
If an atom has a charge of +1, which of the following must be true?
answer
It has one more proton than it does electrons.
question
Elements found on the left side of the periodic table contain outer shells that are _____; these elements tend to form _____ in solution.
answer
almost empty; cations.
question
An atom has four electrons in its valence shell. What types of covalent bonds is it capable of forming?
answer
single, double, or triple.
question
When are atoms most stable?
answer
when all of the electron orbitals in the valence shell are filled.
question
When the atoms involved in a covalent bond have the same electronegativity, what type of bond results?
answer
a nonpolar covalent bond.
question
Nitrogen (N) normally forms three covalent bonds with a valence of 5. However, ammonium has four covalent bonds, each to a different hydrogen (H) atom (H has a valence of 1). What do you predict to be the charge on ammonium?
answer
+1.
question
You need to write down information about a molecule, but need to indicate only the type and number of atoms it contains. Which representation would work best?
answer
molecular formula.
question
You need to represent a molecule to best illustrate the relative sizes of the atoms involved and their interrelationships. Which representation would work best?
answer
space-filling model.
question
Which of the following is true for this reaction?
answer
Ammonia is being formed and decomposed simultaneously.
question
Which of the following correctly describes all chemical equilibrium?
answer
Forward and reverse reactions continue with no net effect on the concentrations of the reactants and products.
question
Which of the following correctly describes a reaction that has reached chemical equilibrium?
answer
The rate of the forward reaction is equal to the rate of the reverse reaction.