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? - carbon, hydrogen, nitrogen, oxygen
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? - iodine
Which of the following statements is false?
1.Carbon, hydrogen, oxygen, and nitrogen are the most abundant elements of living matter
2. some trace elements are very abundant on Earth
3. virtually all organisms require the same elements in the same quantities
4. iron is an example of an element needed y all organisms
5. other than some trace elements, animals are mostly made up of the same elements as plants, in
similar proportions - virtually all organisms require the same elements in the same quantities
What factors are most important in determining which elements are most common in living matter? -
both the relative abundances of the elements and the emergent properties of the compounds made
from these elements
Why is each element unique and different from other elements in chemical properties? - each element
has a unique number of protons in its nucleus
knowing just the atomic mass of an element allows inferences about which of the following? - the
number of protons plus neutrons in the element
in what way are elements in the same column of the periodic table the same? - they have the same
number of electrons in their valence shell
, oxygen has an atomic number of 8 and a mass number of 16. thus, what is the atomic mass of an oxygen
atom? - approximately 16 daltons
the nucleus of nitrogen atom contains 7 neutrons and 7 protons. which of the following is a correct
statement concerning nitrogen? - the nitrogen atom has a mass number of 14 and an atomic mass of
approximately 14 daltons
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? - molybdenum atoms can have
between 50 and 58 neutrons
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? - some carbon
atoms in nature have more neutrons
Atom 1 Atom 2
13
11
HH
Which of the following best describes the relationship between the atoms described above? - they are
isotopes
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? - the element may have multiple stable isotopes,
and the isotopic composition may vary from sample to sample
one different between carbon-12 (12/6 C) is the carbon-14 (14/6 C) has - two more neutrons than
carbon-12
an atom has 6 electrons in its outer shell. how many unpaired electrons does it have? - 2
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