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The four most common elements in living organisms are
C, H, O, N
What is the atomic mass of an atom that has 6 protons, 6 neutrons, and 6 electrons?
12
An uncharged atom of boron has an atomic number of 5 and an atomic mass of 11. How many electrons does boron have?
5
The sodium atom contains 11 electrons, 11 protons, and 12 neutrons. What is the mass number of sodium?
23
Which of the following best describes the atomic number of an atom?
the number of protons in the atom
Typically, nitrogen atoms are composed of electrons, protons, and neutrons. An isotope of nitrogen could
have more neutrons than the usual nitrogen atom.
A radioactive isotope is an isotope that
decays.
Which of the following statements about radioactive isotopes is true?
The energy emitted by radioactive isotopes can break chemical bonds and cause molecular damage in cells.
Which of the following is a trace element in the human body?
zinc
When full, the innermost electron shell of argon contains ________ electrons, and the outermost shell contains ________ electrons.
2; 8
What happens to an atom if the electrons in the outer shell are altered?
The properties of the atom change.
A/an ________ forms when two atoms share electrons.
covalent bond
A hydrogen atom has one electron. How many covalent bonds can hydrogen form?
one
Table salt is formed when
sodium donates its single outer electron to chlorine.
The body uses atoms in different ways to accomplish different tasks. For example, one portion of the body's calcium supply strengthens bones, whereas another portion combines with proteins to stimulate blood clotting after tissue injury. Which of the following statements provides the most logical chemical explanation of calcium's ability to perform such different functions?
The bone contains calcium salts, which are less reactive than the calcium ions found in the blood.
Medicines are often administered in pill form. In many cases, the active ingredient of the pill (the drug) is joined to another substance by ________. This forms a/an ________, which is stable in the dry environment of a pill bottle but dissociates under the wet conditions of the digestive system to release the drug to the body.
ionic bonds; salt
What is the fundamental difference between covalent and ionic bonding?
In a covalent bond, the partners share a pair of electrons; in an ionic bond, one partner accepts electrons from the other.
Which of the following statements regarding the oxygen atom of a water molecule is true?
Oxygen is more electronegative than the hydrogen atoms.
In a water molecule, hydrogen and oxygen are held together by a ________ bond.
polar covalent
Which of the following statements regarding matter is false?
All matter exists in the form of compounds.
A single water molecule (H—O—H) is held together by
two polar covalent bonds
The hydrogen atoms of a water molecule are bonded to the oxygen atom by ________ bonds, whereas neighboring water molecules are held together by ________ bonds.
polar covalent; hydrogen
________ are weak bonds that are not strong enough to hold atoms together to form molecules but are strong enough to form bonds within and around large molecules.
Hydrogen bonds
Water molecules stick to other water molecules because
hydrogen bonds form between the hydrogen atoms of one water molecule and the oxygen atoms of other water molecules.
Which of the following statements regarding chemical reactions is false?
Some chemical reactions create electrons; others destroy them.
In the equation 2 H2 + O2 → 2 H2O, the H2 molecules are ________ and the H2O molecules are ________.
reactants; products
In plants, the process of photosynthesis produces glucose (C6H12O6) and oxygen from carbon dioxide and water. Which of the following statements about photosynthesis is true?
All of the carbon atoms from the carbon dioxide atoms are found in glucose
The tendency of water molecules to stick together is referred to as
cohesion
Water's surface tension and heat storage capacity are accounted for by its
hydrogen bonds.
The temperature of evaporation is much higher for water than for alcohol. Without knowing more about the chemistry of alcohol, which of the following is the most logical chemical explanation for this phenomenon?
Fewer hydrogen bonds form between alcohol molecules. As a result, less heat is needed for alcohol molecules to break away from solution and enter the air.
Which of the following statements best describes a compound?
A compound contains two or more different elements in a fixed ratio.
As ice melts,
hydrogen bonds are broken.
Which of the following statements about water is false?
Ice is more dense than liquid water.
You've made a hot drink by dissolving a teaspoon of instant coffee and a teaspoon of sugar in a cup of hot water. Which of the following statements is true?
You've just prepared an aqueous solution.
Which of the following is dependent on the ability of water molecules to form hydrogen bonds with other molecules besides water?
the universality of water as a solvent
Clots in our blood can lead to a heart attack or stroke by blocking blood flow. If a clot were made up of a mass of proteins, what changed in the proteins to cause them to form the clot?
The proteins were no longer soluble in the blood.
A solution with a pH of 7 is
neutral
Compared to a solution of pH 3, a solution of pH 1 is
100 times more acidic
Which of the following statements about pH is true?
An increase in hydrogen ion concentration means a decrease in pH scale units
Household ammonia has a pH of 12; household bleach has a pH of 13. Which of the following statements about these substances is true?
The ammonia has 10 times as many H+Â ions as the bleach.
In the equation 2 H2 + O2 → 2 H2O,
only H2O is a compound
A buffer
donates H+Â ions when conditions become too basic and accepts H+Â ions when conditions become too acidic
Silicon is an element that is found directly underneath carbon in the periodic table. How many electrons are in the valence shell of a silicon atom?
4
Which of the following trace elements needed by humans is commonly added to table salt?
iodine
In some areas, fluoride is added during the municipal water treatment process in order to help
reduce tooth decay
Which of the following particles are found in the nucleus of an atom?
protons and neutrons
What change is occurring in this figure?
Chlorine is filling its third electron shell.
The figure below shows five water molecules. The hydrogen bonds shown in this figure are each
between an oxygen and a hydrogen atom of different water molecules.
Below is the structure of octane, the major component of gasoline. What type(s) of bond is (are) found in a molecule of octane?
only nonpolar covalent bonds
Below is the structure of leucine, an amino acid. What type of bond is the arrow pointing to?
a polar covalent bond
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