Chapter 2 Flashcards
wood ants
shoot formic acid to defend against invaders
Matter consists of ___ in pure form and in combinations called ___.
chemical elements, compounds.
element
substance that can’t be broken down to other substances by chemical reactions
How many naturally occurring elements are there?
92 elements
compound
substance consisting of 2+ different elements combined in a fixed ratio. (eg. NaCl)
has different characteristics from that of its elements
essential elements
20-25% of the natural elements
needed by an organism to live a healthy life and reproduce
What elements make up 96% of living matter?
carbon, oxygen, hydrogen, nitrogen
trace elements
required by an organism only in minute quantities
What elements are trace elements?
boron, chromium, cobalt, copper, fluorine, iodine, iron, manganese, molybdenum, selenium, silicon, tin, vanadium, zinc
goiter
when the thyroid gland swells to abnormal size due to lack of iodine
arsenic
poisonous to humans
serpentine
jade-like material with elevated concentrations of chromium, nickel, cobalt
evolution of tolerance to serpentine
some plants evolved over time (natural selection) to survive in serpentine soils
An element’s properties depend on the ____.
structure of its atoms.
atom
smallest unit of matter that still retains properties of an element
subatomic particles
make up atoms
neutron, proton (+), electron (-)
atomic nucleus
dense core made of protons and neutrons, surrounded by cloud of electrons (attracted by charge)
mass of proton/neutron
1.7 x 10^-24 g/1 Dalton
dalton
unit of measurement same as 1 amu
atomic number
number of protons of a certain element
written in subscript on the left of the symbol
usually indicates number of electrons as well, IF atom isn’t an ion
mass number
sum of protons + neutrons
superscript to the left of the symbol
atomic mass
total mass of an atom
isotopes
different atomic forms of the same element, with different neutron number
have greater masses
radioactive isotope
unstable, nucleus decays spontaneously, gives off particles and energy
radioactive tracers
radioactive atoms put into bloodstream to diagnose certain disorders (eg. kidney disease)
PET scanners
monitor growth and metabolism of cancers in the body
dangers of decaying isotopes
radioactive fallout
severity depends on amount/type of radiation
radiometric dating
used to date fossils
measure ratio of different isotopes and calculate how many half-lives have passed since an organism was fossilized
half-life
parent isotope decays into daughter isotope
amount of time for 50% of parent to decay
Which subatomic particles are responsible for chem reactions?
electrons
energy
capacity to cause change (eg. by doing work)
potential energy (PE)
energy matter possesses b/c of its location/structure
What is matter’s natural tendency?
to move towards the lowest possible state of potential energy
Skills Exercise: Neanderthal Extinction
- used carbon-14 dating to determine age of Neanderthal fossil from most recent layer
- half-life of carbon-14 is 5,730 years
- fossil had ~ 0.0078 as much carbon-14 as the atmosphere
potential energy of an electron is from:
- their distance from the nucleus; the more distant an electron is from the nucleus, the greater the potential energy
- energy level; can’t exist between energy levels, only at certain ones
electron shells
have characteristic average distance and energy level
where electors are found
represented by concentric circles
first shell = closest to nucleus (lowest PE)
contain electrons at a particular energy level
Can electrons move between shells? How?
Yes, but only by absorbing/losing amount of energy equal to the difference in PE between its position in the old and new shell
When an electron absorbs energy:
it moves to a shell further from the nucleus
When an electron “falls back” to a shell:
the lost energy is released into the enviro as heat
Chemical behavior of an atom is determined by the:
distribution of electrons in the electron shells
How many electrons can the first shell hold?
2 electrons
How many electrons can the second, third, etc shells hold?
8 electrons
The outermost shell determines:
the chemical behavior of an atom, based on the NUMBER of electrons in it
valence shell/valence electrons
the outermost shell and outermost electrons
unpaired electrons react
Atoms with full valence shells will:
not react w/ other atoms; inert
Each concentric circle in a 2D drawing:
represents only the average distance between an electron in that shell and then nucleus
orbital
3D space where an electron is found 90% of the time
component of an electron shell
no more than 2 electrons can occupy a single orbital
4 orbitals of the second electron shell = up to 8 electrons
types of orbitals
1st electron shell: only one spherical s orbital (1s)
2nd electron shell: 4 orbitals, 1 large spherical s orbital (2s), 3 dumbbell-shapped p-orbital (2p orbitals)
Formation and function of molecules depend on ____ between ___
chemical bonding, atoms.
chemical bonds
attractions between atoms that interact
covalent bonds
sharing of a pair of valence electrons by 2 atoms
molecule
2+ atoms held togeterh by covalent bonds
molecular formula
indicates how many atoms in the molecule (eg. H2)
Lewis Dot structure
element symbols are surrounded by dots that represent the valence electrons (eg. H:H)
structural formula
line represents single bond; double bond is two lines (eg. H-H, or O=O)
valence
bonding capacity of an atom corresponding to # of covalent bonds they can form; equals # of unpaired electrons required to complete the atom’s outermost shell
electronegativity
attraction of a particular atom for the electrons of a covalent bond; more electronegative = more strongly it pulls shared electrons toward itself
nonpolar covalent bond
electron is shared equally between 2 atoms; same electronegativity
polar covalent bond
electron not shared equally b/c differing electronegativities (eg. water = very polar b/c oxygen is very electronegative)
partial negative
caused by polar covalent bonds
indicated w/ delta signs
ions
two oppositely charged atoms (b/c electron stripped away from another)
applies to molecules that are electrically charged
cation
positively charged ion
anion
negatively charged ion
ionic bond
bond between any two oppositely charged ions (eg. sodium and chlorine)
ionic compounds/salts
compounds formed by ionic bonds
often found as crystals in nature
made of vast #s of cation ions and anions bound by electrical attraction and arranged in 3D lattice
*IS NOT a molecule
importance of weaker bonds
- two molecules can come together, respond, then separate
eg. water and ionic bond, hydrogen bonds and van der Waals
hydrogen bond
attraction between a hydrogen and an electronegative atom (when covalently bonded w/ electroneg atom, has slight pos charge that allows it to be attracted to diff electroneg atom nearby)
van der Waals interactions
individually very weak; occur only when atoms and molecules are very close together
constantly changing regions of pos/neg charge in molecules
linear shape
molecule consisting of two atoms
Molecule shape is determined by:
position of atoms’ orbitals
(eg. atoms w/ valence electrons in both s and p orbitals form 4 new hybrid orbitals shaped like teardrops from region of atomic nucleus; if connect larger ends w/ lines, have a tetrahedron)
importance of molecular shape
determines how biological molecules recognize and respond to one another / specificity (only bind temporarily if their shapes are complementary)
(eg. opiates, which relieve pain and alter mood by weakly binding to specific receptor mollies on brain cell surfaces; have shapes similar to endorphins)
Chemical reactions ___ and ____ chemical bonds.
make, break
chemical reactions
making/breaking of chemical bonds, leading to changes in composition of matter (eg. hydrogen and oxygen reaction forms water by breaking covalent bonds of H2 and O2 and forming new bonds for H2O)
reactants
starting materials, on L of equations
products
ending materials, on R of equations
In chemical reactions, matter is:
conserved. Reactions can only rearrange electrons
All chemical reactions are:
reversible
factor that affects rate of reaction
concentration of reactants; greater concentration = more collisions = more opportunities to react and form products
chemical equilibrium
point at which the reactions offset one another exactly
is a dynamic equilibrium (reactions still going on) w/ no net effect on reactant/product concentrations
*equilibrium does NOT mean reactants and products are equal in concentration, but that their concentrations have stabilized at a particular ratio (eg. ammonia)
strongest chemical bonds
ionic and covalent
glucose
C6H12O6
alpha glucose vs beta glucose = reversal of H and OH on first carbon
fructose
C6H12O6, placement of C atoms = diff
glycosidic linkage
connects 2 sugar molecules, disaccharide, loses water molecule as does so –> condensation reaction, dehydration reaction
starch
polymer of alpha glucose molecules; energy storage in plant cells
glucogen
polymer of alpha molecules; differs in pattern of polymer branching; energy storage in animal cells
cellulose
[polymer of beta glucose; structural molecule in walls of plants, major componenet of wood
chitin
beta glucose molec w/ N containing group attached to ring; structural molecule in walls of fungus cells; exoskeletons
tryglycerides
fats and oils, 3 fatty acids attached to glycerol molecule
- fatty acids = hydrocarbons (covalently bonded C and H w/ carboxyl group (COOH) at end)
- double bond in fatty acid creates bend –> saturated fats
saturated fats
packed tightly, higher melting point
-single covalent bond btwn each pair of C, each C has 2 H bonded to it (saturated w/ H)
unsaturated fats
- liquid at room temp
- lower melt temp
monounsaturated fatty acid
1 double covalent bond, each of 2 C in bond has only 1 H bonded to it
polyunsaturated fatty acid
2+ double covalent bonds
phospholipid
looks like triglyceride
-one of fatty acid chains replaced by phosphate group
