Ch. 2 Practice test bio 101
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
A sodium atom has a mass number of 23. Its atomic number is 11. How many electrons does it have if it is not an ion?
11
An element has 8 protons, 9 neutrons, and 8 electrons. Its atomic number and atomic mass, respectively, are _____.
8 and 17
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, and 6
There are _____ naturally occurring elements.
92
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.
Evaluate the following statement: Oxygen is not a greenhouse gas; therefore, gases containing oxygen, such as ozone, nitrous oxide, and carbon dioxide, are not greenhouse gases either.
False. Compounds can have emergent properties that are very different from the elements that form them.
Evaluate the following statement: Concentrations of trace elements in an environment above what is required by organisms generally has no effect on those organisms.
False. Elevated concentrations of some trace elements such as cobalt and chromium can be toxic.
Consider a hypothetical atom with an atomic number of 4 and a net electronic charge of +1. How many neutrons does this atom have?
The answer cannot be determined from the information provided.
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.
Which of the following statements describes a reversible reaction that has reached chemical equilibrium?
The rate of the reverse reaction equals the rate of the forward reaction.
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
Isotopes of an element will always differ in _____.
atomic mass
Ionic bonds form as a result of _____.
attraction between ions that have opposite charges
Which of the following is a trace element?
copper
An atom that normally has _____ in its outer shell would not tend to form chemical bonds with other atoms.
eight electrons
Which of the following has negligible mass?
electron
The number of protons in an uncharged atom _____.
equals the number of electrons
For most atoms, a stable configuration of electrons is attained when the atom _____.
has eight electrons in its outermost shell
A polar covalent bond is a bond that _____.
has shared electrons pulled closer to the more electronegative atom
Potassium (atomic number 19, mass number 40) and sodium (atomic number 11, mass number 23) have similar chemical properties and reactive behavior. This is because uncharged atoms of potassium and sodium _____.
have different mass numbers and each has one electron in its outermost electron shell
What are the four most abundant elements found in living systems?
hydrogen, oxygen, nitrogen, and carbon
A hydrogen bond _____.
is a weak chemical bond
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
A covalent bond is likely to be polar if _____.
one of the atoms sharing electrons is much more electronegative
Hydrogen bonds occur when _____.
partial opposite charges on molecules come close enough to attract each other
A neutral atom of chlorine has an atomic number of 17. It has _____ electrons in its third shell.
seven
An uncharged atom of nitrogen (atomic number = 7) has _____.
seven protons and seven electrons
How many electrons would be present in the valence shell of a sulfur atom (atomic number 16, mass number 32)?
six electrons
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
Radioactive isotopes are useful in scientific research because _____.
they can be used as tracers to follow particular atoms and molecules through metabolic pathways
Phosphorus-32 (radioactive) has _____ than phosphorus-35 (normal).
three fewer neutrons