Ch. 2 AP Bio
Atoms can be represented by simply listing the number of protons, neutrons, and electrons—for example, 2p+; 2n0; 2e- for helium. Which one of the following lists represents the 18O isotope of oxygen?
8p+; 10n0; 8e-
There are _____ naturally occurring elements.
92
When one or more pairs of valence electrons are shared by two atoms, what type of bond is formed?
A covalent bond.
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 3-dimensional shapes of large molecules.
What has negligible mass?
Electron, because the mass of an electron is only about 1/2,000 that of a proton or neutron, electrons are not considered when computing atomic mass.
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.
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
What are the four most abundant elements found in living systems?
Hydrogen, oxygen, nitrogen, and carbon
What coefficients must be placed in the following blanks so that all atoms are accounted for in the products?C6H12O6 → _____ C2H6O + _____CO2
2; 2
Phosphorus-32 (radioactive) has _____ than phosphorus-35 (normal).
3 fewer neutrons
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
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.
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 loss or gain of an electron(s) does not influence mass number, defined as the number of protons plus the number of neutrons in the nucleus of an atom.
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.
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 correctly describes any chemical reaction that has reached equilibrium?
The rates of the forward and reverse reactions are equal.
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 charge
Which of the following is a trace element?
copper
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 8 electrons in its outermost shell
A polar covalent bond is a bond that _____.
has shared electrons pulled closer to the more electronegative atom
The reactivity of an atom arises from
the existence of unpaired electrons in the valence shell.
atomic number is equal to
number of protons
The compound CaSO4 ionizes into a calcium ion and a sulfate ion (SO4). Calcium has 2 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
How many electrons would be present in the valence shell of a sulfur atom (atomic number 16, mass number 32)?
6 electrons
Atomic chlorine has an atomic number of 17. It has _____ electrons in its third shell.
7
An uncharged atom of nitrogen (atomic number = 7) has _____.
7 protons and 7 electrons
An element has 8 protons, 9 neutrons, and 8 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
Radioactive isotopes are useful in scientific research because _______.
They can be used as tracers to follow particular atoms and molecules through metabolic pathways.
Which of the following statements is true about chemical reactions?
They involve the making and breaking of chemical bonds.
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 1 electron in its outermost electron shell
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)
What subatomic particles has appreciable mass and lacks a charge?
neutron, a neutron weighs about 1.7 x 10-24 grams (has a mass close to 1 dalton), and it is electrically neutral.
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
Hydrogen bonds occur when _____.
partial opposite charges on molecules come close enough to attract each other
In the term trace element, the modifier trace means
the element is required in very small amounts.
