BIO Chapter 2 Practice Questions
The compound CaSO4 ionizes into a calcium ion and a sulfate ion (SO4). Calcium has two electrons in its outer shell. Upon ionization, what would you expect the charge on the sulfate ion to be?
-2
How many electrons are involved in a single covalent bond?
2
What coefficients must be placed in the following blanks so that all atoms are accounted for in the products? C6H12O6 S _____ C2H6O + _____ CO2
2; 2
Phosphorus-32 (radioactive) has __________ than phosphorus-35 (normal)
3 fewer neutrons
How many electrons would be present in the valence shell of a sulfur atom (atomic number 16, mass number 32)?
6 electrons
A neutral atom of chlorine has an atomic number of 17. It has __________ electrons in its third shell.
7
An element has eight protons, nine neutrons, and eight electrons. Its atomic number and atomic mass, respectively, are __________.
8 and 17
An atom that normally has __________ in its outer shell would NOT tend to form chemical bonds with other atoms
8 electrons
A particular carbon isotope has an atomic number of 6 and an atomic mass of 14. The respective number of neutrons, protons, and electrons that this carbon isotope has is __________.
8,6,6
We can represent atoms by listing the number of protons, neutrons, and electrons-for example, 2p+, 2n0, 2e- for helium. Which of the following represents the 18O isotope of oxygen?
8p+, 10n0, 8e-
There are __________ naturally occurring elements
92
Which of the following can be attributed to water's high specific heat?
A lake heats up more slowly than the air around it.
Which of the following four statements, if any, is true regarding essential elements and living organisms?
Although all forms of life require iron, other elements are required only by certain species.
What is the role of van der Waals interactions in biological molecules?
Although they are weak bonds, van der Waals interactions help to reinforce the three-dimensional shapes of large molecules.
Consider this statement: Oxygen is not a greenhouse gas; therefore, gases containing oxygen—such as ozone, nitrous oxide, and carbon dioxide—are not greenhouse gases either. Which of the following is a valid response to this statement?
False. Compounds can have emergent properties that are very different from those of the elements that form them.
Consider this statement: Concentrations of trace elements in an environment above what is required by organisms generally have no effect on those organisms. Which of the following is a valid response to this statement?
False. Elevated concentrations of some trace elements such as cobalt and chromium can be toxic.
The atomic number of sulfur is 16. Sulfur combines with hydrogen by covalent bonding to form a compound, hydrogen sulfide. Based on the number of valence electrons in a sulfur atom, predict the molecular formula of the compound.
H2S
Consider a hypothetical atom with an atomic number of 4 and a net charge of +1. How many neutrons does this ion have?
The answer cannot be determined from the information provided. Correct. All the atoms of an element have the same number of protons, but some atoms have different numbers of neutrons than other atoms of the same element; therefore, the atoms have different mass numbers. Without the mass number (number of protons + neutrons), it is not possible to determine the number of neutrons.
Which statement is true of all atoms that are anions?
The atom has more electrons than protons.
Copper has an atomic number of 29 and a mass number of 64. What would result if an uncharged copper atom lost two electrons?
The atomic number would remain 29, the mass number would remain 64, and the atom would be a cation with a +2 charge.
The cities of Portland, Oregon, and Minneapolis, Minnesota, are at about the same latitude, but Minneapolis has much hotter summers and much colder winters than Portland. Why?
The ocean near Portland moderates the temperature.
Which of the following statements correctly describes any chemical reaction that has reached equilibrium?
The rates of the forward and reverse reactions are equal.
Which of the following statements is true about chemical reactions?
They involve the making and breaking of chemical bonds.
When one or more pairs of valence electrons are shared by two neutral atoms, what type of bond is formed?
a covalent bond
The most common form of calcium has 20 protons, 20 neutrons, and 20 electrons. Which of the following elements would be an isotope of calcium?
an atom with 20 protons, 21 neutrons, and 20 electrons
If you change the number of neutrons in an atom, you create _____.
an isotope
In which of the following will isotopes of an element always differ?
atomic mass
Ionic bonds form as a result of __________.
attraction between ions that have opposite charges
Why are radioactive isotopes useful in scientific research?
because they can be used as tracers to follow particular atoms and molecules through metabolic pathways
Which of the following is a trace element?
copper
Which of the following has negligible mass?
electron
The number of protons in an uncharged atom __________.
equals the number of electrons
Which of the following statements describes a reversible reaction that has reached chemical equilibrium?
he rate of the reverse reaction equals the rate of the forward reaction.
What are the four most abundant elements found in living systems?
hydrogen oxygen nitrogen carbon
When the proton number and electron number are unequal, the atom or molecule __________.
is an ion
Which of the following molecules has the shape of a completed tetrahedron?
methane (CH4)
Which of the following subatomic particles has appreciable mass and lacks a charge?
neutron
The chemical characteristics or reactivity of an element depend mostly on the __________.
number of electrons in its outermost shell
Some groups of elements react chemically in similar ways. For example, the chemistry of sodium and the chemistry of lithium are similar. The chemistry of chlorine and the chemistry of iodine are also similar. These similarities in chemistry result when different elements have similar __________.
numbers of outer-shell electrons
Compared with 31P, the radioactive isotope 32P has
one more neutron.
A covalent bond is likely to be polar if __________.
one of the atoms sharing electrons is much more electronegative than the other
In a single molecule of water, two hydrogen atoms are bonded to a single oxygen atom by _____.
polar covalent bond
A hydrogen bond __________.
s a weak chemical bond
An uncharged atom of nitrogen (atomic number = 7) has __________.
seven protons and seven electrons
In the term trace element, the adjective trace means that
the element is required in very small amounts.
The reactivity of an atom arises from
the existence of unpaired electrons in the valence shell.
Pharmaceutical researchers are often interested in blocking particular receptor proteins on cell surfaces. What chemical property of a molecule would be most important for this type of application?
the molecule's shape
When do hydrogen bonds occur?
when partial opposite charges on molecules come close enough to attract each other
For most atoms, when is a stable configuration of electrons attained?
when the atom has eight electrons in its outermost shell