Mastering A&P: Chapter 2

Calcium's atomic number is 20. It forms ions with 18 electrons. What is the electrical charge of a calcium ion? 1) +2 2) -1 3) +1 4) -2

1) +2 With atomic number 20, calcium atoms have 20 positive protons, and the ion has only 18 electrons, which means the net charge is +2. Calcium ions are essential for muscle contractions, nerve impulses, and bone maintenance.

Which of the following is an example of a decomposition reaction? 1) MgO2 → Mg + O2 2) H2 + O → H2O 3) MgSO4 + 2NaCl → MgCl2 + Na2SO4 4) 2Na + Cl2 → 2NaCl

1) MgO2 → Mg + O2 A decomposition reaction occurs when a larger molecule is broken down into smaller molecules or its constituent atoms.

Which of the following is NOT a difference between a compound and a mixture? 1) Mixtures are homogeneous while compounds are heterogeneous. 2) Some mixtures are homogenous, while others are heterogeneous. All compounds are homogeneous. 3) Mixtures can be separated by physical means, for example, straining, filtering, or evaporation. Compounds can only be separated into their constituent atoms by chemically breaking bonds. 4) No chemical bonding occurs between the components of a mixture. The properties of atoms and molecules are not changed when they become part of a mixture.

1) Mixtures are homogeneous while compounds are heterogeneous. Mixtures differ from compounds in several important ways. (1) The chief difference between mixtures and compounds is that no chemical bonding occurs between the components of a mixture. The properties of atoms and molecules are not changed when they become part of a mixture. (2) Depending on the mixture, its components can be separated by physical means, straining, filtering, evaporation, and so on. Compounds, by contrast, can be separated into their constituent atoms only by chemical means (breaking bonds). (3) Some mixtures are homogenous, while others are heterogeneous. All compounds are homogeneous.

The major function of RNA is to carry out the genetic instructions for protein synthesis. 1) True 2) False

1) True The major function of RNA is to carry out the genetic instructions (provided by DNA) for protein synthesis.

Which of the following is NOT a subatomic particle? 1) molecule 2) neutron 3) electron 4) proton

1) molecule Atoms are comprised of subatomic particles: protons, electrons and neutrons. Most atoms do not exist in the free state, but instead are chemically combined with other atoms. Such a combination of two or more atoms held together by chemical bonds is called a molecule.

When an ionic bond forms, which part(s) of the atoms are directly involved? 1) the outermost electrons 2) the protons 3) the neutrons 4) both the protons and the electrons

1) the outermost electrons In ionic bonding, the atoms' outermost electrons—the valence electrons—are closest to each other and will interact, which leads to bond formation.

Atomic number is equal to the number of neutrons in an atom's nucleus. 1) True 2) False

2) False The atomic number of any atom is equal to the number of protons, not neutrons, in its nucleus.

The three atoms shown differ in the number of ___. 1) electrons 2) neutrons 3) positrons 4) protons

2) neutrons Note that these atoms each contain one proton, and therefore variations of the same element that each differ in the number of neutrons.

Based on the information in this figure, we can conclude that chlorine has an atomic number of ___. 1) 11 2) 10 3) 18 4) 17

4) 17 The unbounded chlorine atom has 17 electrons. Therefore, chlorine must have 17 protons and an atomic number of 17.

Which of the following is NOT considered a form of matter? 1) oxygen gas 2) blood 3) bone 4) X rays

4) X rays They are a type of energy.

The three atoms shown represent three unique ___. 1) molecules 2) isotopes 3) cells 4) elements

4) elements The three atoms each contain different numbers of protons and are therefore unique elements.

The lines drawn between hydrogen (H) atoms and the oxygen (O) atom in the structural diagram presented in the right of the figure each represent a ___. 1) polar covalent bond 2) ionic bond 3) hydrogen bond 4) non polar covalent bond

1) polar covalent bond A covalent bond in which electrons are shared unequally is termed a polar covalent bond.

Which type(s) of subatomic particles can be located within the nucleus of an atom? 1) protons and neutrons 2) electrons only 3) protons and electrons 4) neutrons only

1) protons and neutrons In a typical atom, the protons and neutrons "hang out" together in the center of the atom—the nucleus. Electrons are always found orbiting around the nucleus.

Which of the following best defines covalent bonds? 1) the bond formed when shared electrons occupy a single orbital common to both atoms within a molecule 2) the bond formed by the transfer of one or more electrons from one atom to the other 3) the bond formed when sodium and chlorine atoms interact 4) the bond that forms when a hydrogen atom, already covalently linked to one electronegative atom, usually a nitrogen or oxygen, is attracted by another electron-hungry atom, so that a bridge forms between them

1) the bond formed when shared electrons occupy a single orbital common to both atoms within a molecule Electron sharing produces molecules in which the shared electrons occupy a single orbital common to both atoms, which constitutes a covalent bond.

Except for elements 1 and 2, all other elements are stable with how many electrons in their outermost (valence) energy level? 1) 2 2) 8 3) 32 4) 18

2) 8 Elements 1 and 2 are stable with a maximum of two electrons in their outermost (valence) energy level (electron shell). All other elements are stable with eight electrons in their valence shell.

An atom of oxygen has an atomic number of 8 and a mass number of 18. How many of each type of subatomic particle does it contain? 1) The atomic number and the mass number do not provide enough information to determine how many of each subatomic particle is present. 2) 8 protons, 8 electrons, and 10 neutrons 3) 8 protons, 8 neutrons, and 8 electrons 4) 26 total subatomic particles

2) 8 protons, 8 electrons, and 10 neutrons The atomic number is the number of protons in an atom, and it will have the same number of electrons, to balance the electrical charge. Mass number is the number of protons plus the number of neutrons, so subtracting atomic number from mass number reveals the number of neutrons. The number of protons and electrons is constant for all atoms of any element, but the number of neutrons can vary. Atoms of the same element that differ in the number of neutrons are called isotopes.

Suspensions may also be called emulsions. 1) True 2) False

2) False Colloids, not suspensions may also be called emulsions. Colloids are heterogeneous mixtures, meaning their composition is dissimilar in different areas of the mixture. Colloids often appear translucent or milky and although the solute particles are larger than those in true solutions, they still do not settle out. Suspensions are heterogeneous mixtures with large, often visible solutes that tend to settle out.

Nonpolar molecules are the result of unequal electron pair sharing. 1) True 2) False

2) False Polar molecules are the result of unequal electron pair sharing. Nonpolar molecules are electrically balanced due to the equal sharing of electrons between the atoms of the molecules.

Kidneys play a major role in helping to maintain proper levels of Na+ and K+ ions in the blood. If the kidneys fail to function properly, one of the direct consequences would be ___. 1) salt deposits in many regions of the body 2) impaired nerve impulse transmission 3) the blood becoming too concentrated 4) all of the above

2) Impaired nerve impulse transmission Salts are ions that contribute to the ability of nerves to conduct an electrical current.

How do ions form ionic bonds? 1) One atom swaps all of its negative electrons for all of the other atom's positive protons. 2) Ions of opposite electrical charges are attracted to each other to balance the charges. 3) Two atoms come together to share their electrons. 4) Ions of the same type are drawn together because they are attracted to their own kind.

2) Ions of opposite electrical charges are attracted to each other to balance the charges. Ions of opposite charges are drawn together to balance out their charges. Once they bond, they form an ionic compound that can store and transport the ions, or dissociate (separate), releasing the ions, which can then be used by the body.

What explains the negative charge on the oxygen atom within the water molecule? 1) Electrons are transferred from hydrogen to oxygen during the formation of an ionic bond. 2) Oxygen atoms have a stronger pull on the electrons shared within a covalent bond formed between oxygen and hydrogen. 3) Protons are transferred from oxygen to hydrogen during the formation of an ionic bond. 4) Hydrogen atoms have a stronger pull on the electrons shared within a covalent bond formed between oxygen and hydrogen.

2) Oxygen atoms have a stronger pull on the electrons shared within a covalent bond formed between oxygen and hydrogen. Oxygen atoms are highly electronegative and pull electrons away from the electropositive hydrogen atom.

Which of the following is NOT one of the three basic steps involved in enzyme activity? 1) The enzyme releases the product(s) of the reaction. 2) The substrate absorbs chemical energy from the enzyme after binding to its active site. 3) The enzyme's active site binds to the substrate(s) on which it acts, temporarily forming an enzyme-substrate complex. 4) The enzyme-substrate complex undergoes internal rearrangements that form the product(s).

2) The substrate absorbs chemical energy from the enzyme after binding to its active site. Enzymes do not provide energy to their substrates. In fact, enzymes are completely unchanged by their catalytic role and can act again and again.

Which of the following is not a result of hydrogen bonds? 1) Some hair is straight, some wavy, and some very curly. 2) Two hydrogen atoms join together to form a molecule of hydrogen gas. 3) Two strands of DNA are linked together taking a shape similar to a ladder. 4) An enzyme has a unique shape that allows it to bond only with specific molecules.

2) Two hydrogen atoms join together to form a molecule of hydrogen gas. Hydrogen bonds occur when there are polar covalent molecules present, but hydrogen atoms join with each other through nonpolar covalent bonds.

The chemical reaction shown at step C is an ___. 1) exergonic dehydration synthesis 2) endergonic dehydration synthesis 3) exergonic hydrolysis 4) endergonic hydrolysis

2) endergonic dehydration synthesis This figure shows a dehydration synthesis reaction between two monomers forming, resulting in a larger molecule. Building larger molecules (an anabolic reaction) typically requires energy input (as indicated by the red arrow in the figure). Energy-requiring (as opposed to energy-releasing) reactions are termed endergonic.

What type of bond is formed between the oxygen atom of one water molecule and the hydrogen atom of another water molecule? 1) polar covalent bond 2) hydrogen bond 3) non polar covalent bond 4) ionic bond

2) hydrogen bond The attraction between the slightly negative oxygen atom of one molecule and the slightly positively charged hydrogen atom within a separate water molecule is the basis of hydrogen bond formation.

Bonds between carbon and hydrogen atoms (as depicted on the right side of the figure) are generally ___. 1) polar covalent bonds 2) non polar covalent bonds 3) ionic bonds 4) hydrogen bonds

2) non polar covalent bonds Neither carbon nor hydrogen is considered electronegative atoms. Therefore, neither atom has an overly strong pull on shared electrons, and those electrons are shared equally within a nonpolar covalent bond.

Sulfur is atomic number 16. Sulfur will form chemical bonds in a similar manner as ___. 1) hydrogen 2) oxygen 3) nitrogen 4) carbon

2) oxygen Oxygen and sulfur both have six electrons in their valence (outermost) electron shells. Therefore, they will form similar types and numbers of bonds with other atoms.

Formation of hydrogen bonds requires hydrogen atoms and what else? 1) oxygen 2) polar covalent bonds 3) water 4) ionic bonds

2) polar covalent bonds Hydrogen gets a slight positive charge from the unequal sharing of electrons in polar covalent bonds, and it bonds to another atom with a slightly negative charge, again resulting from unequal electron sharing due to a polar covalent bond.

A molecule of water (H2O) is formed by what type of bond? 1) ionic covalent bonds 2) polar covalent bonds 3) non polar covalent bonds 4) weak bonds

2) polar covalent bonds The unequal electron distribution produces a slight negative charge on the oxygen and a slight positive charge on the hydrogens. These slight charges give water many unique characteristics that make it ideal for many physiological processes.

Which particle is indicated by the arrow? 1) electron 2) proton 3) atom 4) neuron

2) proton Note how the number of the indicated particles in each of the three atoms defines each as a unique element.

What is the most significant factor in the formation of a covalent bond? 1) the complete transfer of one or more electrons from one atom to another 2) the sharing of electron pairs between two atoms 3) the transfer of one or more protons from one atom to another 4) the attraction of a hydrogen atom nucleus to the electrons of another atom

2) the sharing of electron pairs between two atoms Covalent bonds are formed by the sharing of electrons between two reactive atoms.

What are the two fundamental roles of DNA? 1) to provide and carry out the instructions for protein synthesis 2) to provide the instructions for protein synthesis, and replicate itself before cell division 3) to carry out the orders for protein synthesis issued by RNA, and to control genetic expression by shutting down genes or altering their expression 4) to provide the instructions for RNA synthesis

2) to provide the instructions for protein synthesis, and replicate itself before cell DNA has two fundamental roles: (1) to replicate itself before the cell divides, ensuring that all genetic information in the descendant cells is identical; and (2) to provide the basic instructions for building every protein in the body.

What is the primary energy-transferring molecule in cells? 1) DNA 2) TACT 3) ATP 4) RNA

3) ATP When broken (cleaved), the high-energy phosphate bonds in the ATP molecule release the energy used to do cellular work.

In a covalent bond, 1) An atom loses electrons to another to gain stability. 2) An atom gains one or more electrons from another atom to gain stability. 3) Atoms share one or more pairs of electrons. 4) Adjacent atoms share a single electron.

3) Atoms share one or more pairs of electrons In covalent bonds, atoms share ("co") their valence electrons ("valent"). These bonds are strong because to maintain stability the atoms must stay close enough together to continue sharing their electrons.

Which of the following distinguishes hydrogen bonds from covalent bonds? 1) Only hydrogen bonds can form within molecules. 2) Only ionic bonds can form within molecules. 3) Only hydrogen bonds can form between molecules. 4) Only covalent bonds can form between molecules.

3) Only hydrogen bonds can form between molecules. Because hydrogen bonds are not true bonds, they do not always join atoms together within a single molecule. In water, for example, hydrogen bonds link water molecules together. This is referred to as an intermolecular attraction—it is between different atoms.

Which of the following is not one of the four basic elements that comprise approximately 96% of a human's body weight? 1) Hydrogen 2) Carbon 3) Potassium 4) Oxygen

3) Potassium

Which of the following best describes an isotope? 1) structurally variant atoms, which always have a mass number of 1 2) structurally variant atoms, which have the same number of neutrons and protons, but differ in the number of electrons they contain 3) structurally variant atoms, which have the same number of protons and electrons, but differ in the number of neutrons they contain 4) structurally variant atoms, which have the same number of neutrons and electrons, but differ in the number of protons they contain

3) Structurally variant atoms, which have the same number of protons and electrons, but differ in the number of neutrons they contain Nearly all known elements have two or more structural variations called isotopes, which have the same number of protons and electrons, but differ in the number of neutrons they contain.

Which of the following is true of polar covalent bonds? 1) Electrons are shared equally. 2) The same number of electrons are gained by one atom as are lost by another. 3) The electrons are shared unequally. 4) They are rather weak bonds.

3) The electrons are shared unequally. Because the electrons are shared unequally, they spend more time around one atom than the other, causing a slight negative charge where they tend to hang out the most, and a slight positive charge where they spend the least time.

Which of the following is FALSE? 1) With some exceptions, matter can be seen, smelled, and felt. 2) Matter exists in solid, liquid, and gaseous states. 3) The weight of matter remains constant wherever it is located. 4) The mass of matter remains constant wherever is it located.

3) The weight of matter remains constant wherever it is located. The mass if an object is equal to the actual amount of matter in the object, and it remains constant wherever the object is. In contrast, weight varies with gravity. Matter is anything that occupies space and has mass. With some exceptions, it can be seen, smelled and felt. Matter exists in solid, liquid, or gaseous states.

What do these four elements have in common? 1) They all have the same number of protons in their nuclei. 2) They all have the same number of electrons in their first electron shell. 3) They all have an incomplete valence electron shell. 4) They are all generally unreactive elements.

3) They all have an incomplete valence electron shell. The valence shell is the outermost electron energy level. Valence shell electrons determine the reactivity of an element.

What is an ion? 1) an atom that loses all of its protons 2) an atom that has lost one or more neutrons 3) an atom that has either gained or lost electron(s) 4) an atom that is sharing electrons with another atom

3) an atom that has either gained or lost electron(s) Ions form when atoms gain or lose electrons to attain a full valence shell, which gives them an electrical charge. Ions can be stored in the body, such as ions of calcium and phosphate that are stored in our bones, or can be available individually for many physiological processes. For example, Na+ is required for muscle contraction, nerve impulse conduction, and regulation of blood pressure.

If an oxygen atom were to form a chemical bond in which it gained two electrons, it would ___. 1) not change in terms of relative stability 2) become less stable 3) become more stable

3) become more stable The addition of two electrons to the second electron shell of an oxygen atom would complete that energy level and result in increased stability.

Covalent bonds: 1) always result in equal distribution of electrons between the atoms. 2) always result in slight electrical charges at different atoms. 3) involve the sharing of one to three pairs of electrons. 4) involve the sharing of 8 pairs of electrons.

3) involve the sharing of one to three pairs of electrons. In single covalent bonds, one pair of electrons is shared; in double covalent bonds two pairs are shared; and triple covalent bonds involve sharing of three pairs of electrons. Double covalent bonds are common between carbon atoms in some organic molecules.

Which subatomic particles contribute to an atom's mass number but not its atomic number? 1) None of them - atomic number and atomic mass number are essentially the same thing. 2) electrons 3) neutrons 4) protons

3) neutrons Atomic number is the number of protons in an atom, but mass number is calculated by adding both the number of protons and the number of neutrons in an atom.

Which of the following is TRUE of atomic weight? 1) Atomic weight is determined by the number of electrons in an atom of a given element. 2) Atomic weight of an element is approximately equal to the number of protons in its nucleus. 3) Atomic weight of an element is calculated by adding the masses of its protons and electrons. 4) Atomic weight of an element is approximately equal to the mass number of its most abundant isotope.

4) Atomic weight of an element is approximately equal to the mass number of its most abundant isotope. Atomic weight is an average of the relative weights (mass numbers) of all the isotopes of an element, taking into account their relative abundance in nature. As a rule, the atomic weight of an element is approximately equal to the mass number of its most abundant isotope.

Which of the following is TRUE regarding the pH of a solution? 1) The fewer hydroxyl ions in a solution, the more basic the solution is. 2) The fewer hydrogen ions in a solution, the more acidic the solution is. 3) The more hydroxyl ions in a solution, the more acidic the solution is. 4) The more hydrogen ions in a solution, the more acidic the solution is.

4) The more hydrogen ions in a solution the more acidic the solution is. The more hydrogen ions in a solution, the more acidic the solution is.

After the transfer of the electron, sodium will form an ion with ___. 1) an atomic number of 10 2) an atomic number of 18 3) a charge of -1 4) a charge of +1

4) a charge of +1 If sodium loses an electron, it will be positively charged. Although not shown explicitly in the figure, the element sodium contains 11 protons within its nucleus. If sodium forms a cation containing 10 electrons, it will have a charge of +1.

What holds the sodium and chloride ions together in a chemical bond? 1) the sharing of a pair of electrons 2) the attraction between their respective nuclei 3) the sharing of a pair of protons 4) an electrical attraction between opposite charges

4) an electrical attraction between opposite charges The transfer of an electron results in ions with opposite charges that are electrically attracted to each other.

Which four elements comprise approximately 96% of our body weight? 1) carbon, oxygen, hydrogen, and potassium. 2) carbon, oxygen, iron, and potassium. 3) carbon, oxygen, potassium, and sodium. 4) carbon, oxygen, hydrogen, and nitrogen.

4) carbon, oxygen, hydrogen, and nitrogen. Four elements: carbon, oxygen, hydrogen, and nitrogen make up about 96 percent of our body weight; 20 others are present in the body, some in trace amounts.

Which of the following correctly ranks the types of chemical bonds, in order, from strongest to weakest? 1) ionic, hydrogen, covalent 2) hydrogen, ionic, covalent 3) hydrogen, covalent, ionic 4) covalent, ionic, hydrogen

4) covalent, ionic, hydrogen In covalent bonds, electrons are shared between atoms; in ionic bonds electrons are lost or gained; but hydrogen bonds are not true chemical bonds—they are weak attractions due to slight electrical imbalances. No electrons are directly involved.