2 Chemical Context of Life Flashcards
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
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.
One difference between carbon-12 ( ) is that carbon-14 ( ) has
two more neutrons than carbon-12.
An atom has 6 electrons in its outer shell. How many unpaired electrons does it have?
2
Electrons exist only at fixed levels of potential energy. However, if an atom absorbs sufficient energy, a possible result is that
an electron may move to an electron shell farther away from the nucleus.
Atoms whose outer electron shells contain 8 electrons tend to
) be both chemically inert and gaseous at room temperature
A covalent chemical bond is one in which
outer-shell electrons of two atoms are shared so as to satisfactorily fill the outer electron shells of both atoms.
When two atoms are equally electronegative, they will interact to form
nonpolar covalent bonds.
What results from an unequal sharing of electrons between atoms?
a polar covalent bond
A covalent bond is likely to be polar when
one of the atoms sharing electrons is much more electronegative than the other atom.
What is the difference between covalent bonds and ionic bonds?
Covalent bonds involve the sharing of electrons between atoms; ionic bonds involve the electrical attraction between atoms.
Which of the following is not considered to be a weak molecular interaction?
a covalent bond
Van der Waals interactions result when
electrons are not symmetrically distributed in a molecule.
A group of molecular biologists is trying to synthesize a new artificial compound to mimic the effects of a known hormone that influences sexual behavior. They have turned to you for advice. Which of the following compounds is most likely to mimic the effects of the hormone?
a compound with the same three-dimensional shape as part of the hormone
1 mole (mol) = (Avogadro’s number)
6.02 x 10 23 molecule
The type of bonding and the numbers of covalent bonds an atom can form with other atoms is determined by _____.
the number of unpaired electrons in the valence shell
An ionic bond is formed when _____.
one atom transfers an electron to another atom
Hydrogen bonding is most often seen _____.
when hydrogen is covalently bonded to an electronegative atom
The tendency of an atom to pull electrons toward itself is referred to as its _____.
electronegativity
