Chapter 2 Flashcards
atomic number
the atomic number corresponds to the number of protons
atomic weight
corresponds to the number of the protons plus neutrons
why does the atomic weight appear in decimal form?
the decimal results from the fact that the atomic weight is an average of all naturally occurring forms of the element, which vary in the number of neutrons
how many naturally occurring elements are there on earth?
92
How many elements are found inside living organisms?
25
How many trace elements are there?
14
trace elements
required in only tiny amounts within organisms, living cells cannot survive without them.
What four elements make up the bulk of living organisms?
Oxygen (65%), carbon (18.5%), hydrogen (9.5%), and nitrogen (3.3%)
Is a dietary supplement that contains gold beneficial to your body?
No. It is not an element required by living cells.
What are some weird elements that living things like us need to survive?
cobalt, copper, iron, silicon, tin, zinc, chromium
what are the two types of chemical bonds?
ionic and covalent
what are ionic bonds?
a bond formed through the transfer of one or more electrons from one atom to another. Both atoms in the exchange become ions through the donating/receiving of electrons.
what are chemical bonds?
the result of attraction between atoms
isotopes
elements that vary in the number of neutrons and are named according to atomic weight (weight of protons + neutrons), for example, nitrogen-13.
ions
elements that vary in the number of electrons in the electron cloud. ions carry a charge. Named for the amount of extra electrons. (Ex. N^3-)
true or false. atoms are neutrally charged.
True
ions carry only a negative charge (T or F).
False, charges can be either positive or negative, and ions can be positive if they have lost electrons.
What holds together atoms in an ionic bond?
unequal charges created by the transfer of electrons.
What compound is an example of an ionic bond?
NaCl
what are covalent bonds?
bonds formed from the sharing of one or more electrons. Each bond consists of a pair of shared electrons.
what is an example of a covalent bond?
H2O
how are single bonds and double bonds in covalent bonds represented?
single bond: O–O
double bond: O=O
what are the two types of covalent bonds?
nonpolar and polar
nonpolar bond
electrons are shared equally between the two atoms in the bond
what compound has a covalent nonpolar bond
methane gas (CH4)
what compound has a polar covalent bond?
water
polar bond
A bond formed from sharing of electrons where the electrons are more strongly attracted to one atom than the other, resulting in the bond having two oppositely charged poles.
polar and charged mean the same thing. (T or F)
False, something can be polar and be neutrally charged.
what causes the polarity in a polar bond?
Because the electrons are no longer evenly spaced between the two atoms, there is a slightly negative pole (end) and a slightly positive pole.
True or false, a polar covalent bond overall carries no charge.
True
In water, to which element are the electrons more attracted?
The electrons are drawn more to the oxygen nucleus than the hydrogen nucleus.
what is a hydrogen bond?
the bond formed by the facing of negatively charged oxygen ends of water molecules towards the positively charged hydrogen ends of other water molecules.
what forms liquid water as we know it?
the ability of a single water molecule to participate in several hydrogen bonds.
what kind of bond holds the atoms together within a water molecule?
polar covalent bond
what kind of bond acts as the binding force between water molecules?
hydrogen bonds
are bonds between water molecules are strong or weak?
weak
Most liquids do not expand when they freeze (true or false)
true
What allows ice to float on the surface of water?
water expands and the molecules are held farther apart when it freezes
what biological function does the flotation of ice serve?
during winter, a thing layer of floating ice insulates the water below the surface, allowing life to survive until the spring thaw.
what is the molecular structure difference between ice and liquid water?
liquid water molecules jostle, constantly break and reform, while frozen water molecules are held rigidly in place
the structure of liquid water molecules make water an effective what?
solvent
what makes water important for earth’s temperature regulation?
liquid water readily absorbs and releases heat and therefore resists temperature change more than most substances
cohesion
the ability of water molecules to stick together due to hydrogen bonding
what is surface tension?
a film-like surface on which items (like pond skaters) can be suspended (caused by hydrogen bonds)
adhesion
the clinging of one substance to another , causes water droplets to stick to surfaces
in which substance do most life-maintaining chemical reactions occur?
water
aqueous solution
a solution that contains a substance dissolved in water
what determines the pH of a solution?
the concentration of hydrogen ions (H+)
the pH scale runs from __ to __.
0 to 14.
Greater H+ concentrations are indicated by a (lower/higher) pH number.
Lower
Lower pH indicates a more basic solution (T or F)
False
what is an acid?
a chemical that, when dissolved in water, releases H+ ions. an acid has a pH between 0 and 7.
at what pH level do hydrogen ions equal hydroxide (OH-) ions?
7
what are buffers?
chemicals that minimize changes in pH by accepting H+ ions when they are present in excess and donating H+ ions when they are short in supply.
example of how buffers work in the human body
there are chemicals present in blood that counteract a drop in pH (more acidic) that occurs every time you exercise.
what is a base?
A base is a chemical that, when dissolved in water, removes H+ ions from the solution by combining them with OH-. A base has a pH anywhere from 7 to 14.
describe ocean acidification.
ocean acidification is the lowering of pH in the world’s oceans due to the dissolving of excess carbon dioxide. The lowered pH inhibits chemical reactions needed to build skeletons/shells in coral reef ecosystems.
organic compounds
molecules that contain carbon bonded to some other element
why is life considered to be carbon-based?
carbon can bond with up to four other atoms, forming the capacity for large, highly diverse, branched chains that can serve as the basic skeletons for a wide variety of chemical compounds
every organic compound contains a skeleton of ______ atoms.
carbon
How much carbon dioxide from the atmosphere is absorbed by the oceans on a daily basis?
20 million metric tons
What is the chemical reaction responsible for the oceans becoming more acidic?
carbon dioxide reacts with seawater, forming carbonic acid
what edible sea creatures are most at risk due to ocean acidification?
shellfish
what are functional groups?
sets of atoms attached to carbon skeletons.
what is the function of functional groups?
they participate in chemical reactions and as a result determine the overall properties of an organic compound.
examples of functional groups:
ethyl alcohol, amino acids, adenosine triphosphate
what are the four classes of large organic molecules important to life on Earth?
carbohydrates, lipids, proteins, and nucleic acids.
examples of carbohydrates
cellulose and glucose
