Chapter 2: The Context of Life Pt. 1
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
glucose
C6H12O6
Phosphorus-32 (radioactive) has _____ than phosphorus-35 (normal).
three fewer neutrons
A neutral atom of chlorine has an atomic number of 17. It has _____ electrons in its third shell.
7
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
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.
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 is a valid response to this statement?
False. Compounds can have emergent properties that are very different from the elements that form them.
Consider this statement: Concentrations of trace elements in an environment above what is required by organisms generally has no effect on those organisms. Which is a valid response to this statement?
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 charge of +1. How many neutrons does this ion 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.
These elements make up 96% of living matter.
The elements carbon, hydrogen, nitrogen, and oxygen make up 20-25% of living mass.
What 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
Gaining or losing a proton would cause the atom to
become a different element.
a trace element
copper
number of protons plus the number of neutrons
determines an atom's mass number
An atom that normally has _____ in its outer shell would not tend to form chemical bonds with other atoms.
eight electrons
negligible mass
electron
The number of protons in an uncharged atom
equals the number of electrons
Atoms with the same number of electrons in their valence shells
exhibit similar chemical behavior or reactivity.
Covalent bonds
formed between atoms that share one or more pairs of valence electrons.
For most atoms, a stable configuration of electrons is attained when the atom
has eight electrons in its outermost shell
These four elements make up about 96% of living matter.
hydrogen, oxygen, nitrogen, and carbon.
What are the four most abundant elements found in living systems?
hydrogen, oxygen, nitrogen, and carbon. These four elements make up about 96% of living matter.
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 neutrons determine the
isotope
Which of the following molecules has the shape of a completed tetrahedron?
methane (CH4)
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
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
The atomic number is the number of
protons
Isotopes of an element have the same number of
protons but different numbers of neutrons.
the atomic number refers to number of
protons in an atom
An uncharged atom of nitrogen (atomic number = 7) has
seven protons and seven 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
An atom with a complete valence shell is
unreactive
Attraction resulting from the motion of electrons describes
van der Waals interactions.
