Ch. 2 The Chemical Basis of Life Mrs. Dugas
define atomic number
# of protons
what does each element differ in
# of protons, neutrons, & electrons
how much iodine do you need a day & where do people put iodine so we can get enough each day
.15 mg, put in salt
what elements does DNA contain (5)
1. cardon, 2. hydrogen, 3. oxygen, 4. nitrogen, & 5. phosphorus
why are chemicals added to food (3)
1. help preserve it, 2. make it more nutritious, & 3. makes it look better
what elements are our body mostly made of (4)
1. oxygen, 2. carbon, 3. hydrogen, & 4. nitrogen
what are some dangers associated with using radioactive substances (2)
1. uncontrolled exposure can cause damage to molecules in living cells & DNA, & 2. chemical bonds are broken by the emitted energy which causes abnormal bonds to form
how many shells can an atom have & how many electrons can fit in each
1st shell- 2 electrons, 2nd shell- 8 electrons, 3rd shell- 8 electrons
how many elements does life require
25
define trace elements
25 essential elements that are required for life & needed in minute quantities
how many elements are there in nature & what kind of state do only a few of them exist in
92 elements, in a pure state
what is a showcase of the diversity of life on Earth
Amazon rain forest
what is matter composed of
chemical elements
what is at the base level of biological hierarchy
chemicals
what makes up our bodies, other organisms, & the physical environment
chemicals
what does Fluorine do for your body
cleans your teeth
what do atoms in a covalent bond do
continually compete for shared electrons
what is the PET useful for
diagnosing heart disorders & cancer & in brain research
define electron shells
energy levels where electrons are located
define nonpolar covalent bonds
equal sharing, pull of each atom is equal & atom is neutral
what do the arrangements of biological hierarchy usually lead to
formation of living organisms
define molecule
formed when atoms are held together by covalent bonds
where is information about the distribution of electrons found
in the periodic table of elements
how can radioactivity be detected
instruments
what kind of ions attract together
ions with opposite charges
define neutrons & where is it found
is electrically neutral, in nucleus
what can living cells not distinguish between
isotopes of same element
what does a neutron do in an atom
makes atom heavier but doesnt change charge
what does the structural formula show
map of atoms
what are living things composed of
matter
what are radioactive tracers frequently used in
medical diagnosis
define polar molecules
molecules with unequal distribution of charges
does a covalent bond have a charge
no because shared electrons don't change charges
are hydrogen bonds strong
no they are weak
what cant polar dissolve
nonpolar
what determines the chemical properties of the atom
number of electrons in outtermost shell
define hydrogen bond
one attracts to next
what is involved in chemical activity
only electrons
what are water molecules electrically attracted to
oppositely charged regions on neighboring molecules
what does a polar molecule attract
other polar & ionic
what are atoms made of & how many are important for biological compounds
over a hundred subatomic particles, only 3 are important
what does an iodide deficiency prevent
production of thyroid hormones, resulting in Goiter
what do more electronegative atoms do
pull harder
what happens to the pull of molecules of only one element & why does this happen
pull toward each atom is equal because each atom has the same electronegativity
what does hydrogen as part of a polar covalent bond do
share attractions with other electronegative atoms
when you share electrons they are, when you give electrons they are
share electrons- molecules, give electrons- ions
what does the molecular formula show
shows what atoms & how many
define electron & where is it found
single negative charge electrical charge, in electron cloud
define proton & where is it found
single positive electrical charge, in nucleus
define atom
smallest unit of matter that still has properties of an element
what is an example of a compound
sodium & chlorine
define compound
substance consisting of 2 or more different elements combined in a fixed ratio
how do you get the # of neutrons
subtract mass number to the atomic number
define mass number
sum of protons & neutrons in nucleus
what does a positron-emission tomography (PET) detect
the location of injected radioactive materials
what does the ordering of atoms into molecules represent
the lowest level of biological organization
what keeps electrons near the nucleus
the negative charge of electrons & positive charge of protons
what do radioactive compounds used in metabolic processes act as
tracers
what does iron do in your body
transport oxygen
what is important to understand in order to understand life
understand the basic concepts of chemistry
define polar covalent bond
unequal sharing, electrons spend more time near the stronger pulling atom
define isotopes
variations that have same number of protons & electrons but different number of neutrons
define covalent bond
when atoms share outershell electrons
define ionic bond
when attraction holds ions together, donate & receive
what happens when an electron is lost, & when one is gained
when lost- a positive charge occurs, when gained- a negative charge occurs
does an ionic bond have a charge
yes
does oxygen attract shared electrons more strongly than hydrogen
yes
what is polar like
a magnet
define elements
a substance that cannot be broken down to other substances
define matter
anything that occupies space & has mass (weight)
define ion
atom or molecule with an electrical charge reulting from gain or loss of electrons
define octet rule
atoms wanting to fill their outermost electron shell until it is full
what kind of atoms does water have
atoms with different electronegativities
define electronegativity
attraction (pull) for shared electrons
define chemical bond
attraction between atoms
what are some examples of trace elements
boron, chromium, copper, cobalt, & fluorine
how do atoms accomplish filling their outermost electron shell
by sharing, donating, or receiving electrons