Campbell s Biology 9e Reece et al Chapter 2 The Chemical Context of Life This chapter presents basic chemical principles for understanding the chemical context of living organisms from atomic structure to the nature of chemical bonds and an introduction to chemical equilibrium These questions focus on elements most important to life or the study of life including the elements that comprise organic molecules and important trace elements Some isotopes are important in geologic dating and in biological tracer studies How elements participate in forming different types of chemical bonds is essential to mastering subsequent topics on the behavior and properties of biological molecules structures and energy metabolism Multiple Choice Questions 1 About 25 of the 92 natural elements are known to be essential to life Which four of these 25 elements make up approximately 96 of living matter A carbon sodium hydrogen nitrogen B carbon oxygen phosphorus hydrogen C oxygen hydrogen calcium nitrogen D carbon hydrogen nitrogen oxygen E carbon oxygen nitrogen calcium Answer D Topic Concept 2 1 Skill Knowledge Comprehension 2 Trace elements are those required by an organism in only minute quantities Which of the following is a trace element that is required by humans and other vertebrates but not by other organisms such as bacteria or plants A nitrogen B calcium C iodine D sodium E phosphorus Answer C Topic Concept 2 1 Skill Knowledge Comprehension 3 Which of the following statements is false A Carbon hydrogen oxygen and nitrogen are the most abundant elements of living matter B Some trace elements are very abundant on Earth C Virtually all organisms require the same elements in the same quantities D Iron is an example of an element needed by all organisms E Other than some trace elements animals are mostly made up of the same elements as plants in similar proportions Answer C Topic Concept 2 1 Skill Application Analysis 1 Copyright 2011 Pearson Education Inc 4 What factors are most important in determining which elements are most common in living matter A the relative abundances of the elements in Earth s crust and atmosphere B the emergent properties of the simple compounds made from these elements C the reactivity of the elements with water D the chemical stability of the elements E both the relative abundances of the elements and the emergent properties of the compounds made from these elements Answer E Topic Concept 2 1 Skill Synthesis Evaluation 5 Why is each element unique and different from other elements in chemical properties A Each element has a unique atomic mass B Each element has a unique atomic weight C Each element has a unique number of protons in its nucleus D Each element has a unique number of neutrons in its nucleus E Each element has different radioactive properties Answer C Topic Concept 2 2 Skill Knowledge Comprehension 6 Knowing just the atomic mass of an element allows inferences about which of the following A the chemical properties of the element B the number of protons in the element C the number of neutrons in the element D the number of protons plus neutrons in the element E both the number of protons and the chemical properties of the element Answer D Topic Concept 2 2 Skill Application Analysis 7 In what way are elements in the same column of the periodic table the same A They have the same number of protons B They have the same number of neutrons C They have the same number of electrons D They have the same number of electrons in their valence shell E They have the same number of electron shells Answer D Topic Concept 2 2 Skill Knowledge Comprehension 2 Copyright 2011 Pearson Education Inc 8 Oxygen has an atomic number of 8 and a mass number of 16 Thus what is the atomic mass of an oxygen atom A exactly 8 grams B exactly 8 daltons C approximately 16 grams D approximately 16 daltons E 24 amu atomic mass units Answer D Topic Concept 2 2 Skill Knowledge Comprehension 9 The nucleus of a nitrogen atom contains 7 neutrons and 7 protons Which of the following is a correct statement concerning nitrogen A The nitrogen atom has a mass number of approximately 7 daltons and an atomic mass of 14 B The nitrogen atom has a mass number of approximately 14 daltons and an atomic mass of 7 C The nitrogen atom has a mass number of 14 and an atomic mass of 7 grams D The nitrogen atom has a mass number of 7 and an atomic number of 14 E The nitrogen atom has a mass number of 14 and an atomic mass of approximately 14 daltons Answer E Topic Concept 2 2 Skill Knowledge Comprehension 10 Molybdenum has an atomic number of 42 Several common isotopes exist with mass numbers of 92 94 95 96 97 98 and 100 Therefore which of the following can be true A Molybdenum atoms can have between 50 and 58 neutrons B The isotopes of molybdenum have different electron configurations C The isotopes of molybdenum can have between 50 and 58 protons D The isotopes of molybdenum have between 50 and 58 neutrons and have different electron configurations E The isotopes of molybdenum have between 50 and 58 protons and have different electron configurations Answer A Topic Concept 2 2 Skill Knowledge Comprehension 11 Carbon 12 is the most common isotope of carbon and has an atomic mass of 12 daltons A mole of carbon in naturally occurring coal however weighs slightly more than 12 grams Why A The atomic mass does not include the mass of electrons B Some carbon atoms in nature have an extra proton C Some carbon atoms in nature have more neutrons D Some carbon atoms in nature have a different valence electron distribution E Some carbon atoms in nature have undergone radioactive decay Answer C Topic Concept 2 2 Skill Application Analysis 3 Copyright 2011 Pearson Education Inc 12 Which of the following best describes the relationship between the atoms described below Atom 1 H Atom 2 H A They are isomers B They are polymers C They are isotopes D They contain 1 and 3 protons respectively E They each contain 1 neutron Answer C Topic Concept 2 2 Skill Knowledge Comprehension 13 The precise weight of a mole of some pure elements like silicon Si can vary slightly from the standard atomic mass or even from sample to sample Why A The element may undergo radioactive decay B The element may react with itself and gain or lose subatomic particles C The atoms of the element form chemical bonds with each other and that changes the weight of the element D The element may have multiple stable isotopes and the isotopic composition may vary