Adv. Biology Chapter 2: The Chemical Context of Life
There are _____ naturally occuring elements.
92
Phosphorus-32 (radioactive) has _____ than phosphorus-35 (normal).
3 fewer neutrons
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, and 6
Which is NOT involved in, or is NOT relevant to, hydrogen bonding?
Loss of electrons
Which of the following molecules has the shape of a completed tetrahedron?
Methane (CH4)
Which one of the following does the equation of a chemical reaction NOT tell us?
Speed of the reaction
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.
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 atoms that have opposite charges
Which of the following is a trace element?
copper
Which one 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 8 electrons in its outermost shell
A polar covalent bond is a bond that _____.
has shared electrons pulled closer to the more electronegative atom
Which of the following is NOT a characteristic that makes radioactive tracers useful in medical diagnoses?
they may damage or destroy molecules
Which of the following is NOT one of the four most abundant elements found in living systems?
zinc
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
Every time you move on the pH scale, how much is the difference?
10 times
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
Which of the following statements is NOT true about chemical reactions?
They represent the way matter is created and destroyed.
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
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
Two atoms of the same element must have the same number of _____.
protons
