Ch. 2 Life's Chemical Basis Flashcards
element
most basic form of matter that occupies space, has mass, pure substance;
** 95% of body weight of living organisms are made up of only 4/92 naturally occurring elements** (carbon, hydrogen, oxygen, nitrogen)
atom
smallest particle of an element
atomic structure
how protons, neutrons, electrons are arranged
atomic number
number of protons of one atom in that element
all atoms of that particular element have the same atomic number
mass number
number of protons +number of neutrons
electron levels
shell order: 2,8,16(8 and 8)
isotope
atoms that have different number of neutrons (different mass number)
ex. C12 has 6 protons, 6 neutrons
C14 has 6 protons, 8 neutrons
radioistopes
isotope with unstable nucleus, emits energy– used in medical imaging (MRI, CAT)
breaks down through radioactive decay (alpha, beta, gamma)
free radical
fragment of a molecule that has an ‘unpaired electron’ in its outer electron shell
** very reactive and will pull other electrons away from molecule (carcinogens), damages DNA**
what determines whether atoms will interact?
the number of electrons and arrangement in outer electron shell
chemical bonding
when 2 or more atoms share/gain/give up an electron, links atoms to molecules
molecule
2 or more atoms bonded together
ex. H2
compound
2 or more different elements bonded together in AN EXPECTED RATIO
ex. H2O
mixture
2 or more elements intermingling but not combining
types of mixtures
colloid: particles remain suspended and will not settle out
example: mayonnaise
suspension: particles are suspended but may settle out over time
example: blood
chemical bookkeeping
use symbols for elements when writing formulas
glucose
C6H12O6
photosynthesis’s reactants and products
12H2O+6CO2—->C6H12O6 (sugar) +6CO2+6H2O
law of conservation of mass
matter can not be created or destroyed
types of chemical bonding
- covalent
- ionic
- hydrogen
covalent bonding
atoms share a pair of electrons to fill the outermost shell and create a more stable element
ex. molecular hydrogen (H2)
ionic bonding
atom transfer electrons-- element has gained or lose an electron \+charge: more protons than electrons -charge: more electrons than protons **oxidation: loss of electrons **reduction: gain of electrons
hydrogen bonding
molecule joined to hydrogen by polar covalent bonds
- no true net charge
- oppositely charge atoms attract
what is a water molecule?
- a polar covalent molecule
- oxygen end has a slight negative charge
- hydrogen ends has slight positive charge
properties of water (1)
- shows polarity–causes its cohesiveness
- hydrophilic=polar
- hydrophobic=non-polar
* *water’s cohesion/adhesion causes evapotranspiration (plants get water to tops of trees and leaves**
properties of water (2)
- has temperature stabilizing effects
-evaporation -freezing
-ability to absorb large amounts of heat before
changing temperature
properties of water (3)
- universal solvent
- because ions/ polar molecules easily dissolve in water
solute vs solvent
solute: substance being dissolved
solvent: substance doing the dissolving
why are hydrogen bonds so important
- hydrogen bonds are weaker than covalent bonds
- hydrogen bonds give water its unusual properties
cohesion
like molecules attract
adhesion
unlike molecules attract
what about acids, bases, buffers?
water easily breaks into hydrogen (H+) ions and hydroxide (OH-) ions
**most influential of these ions is the H+ ion
acid
donate H+ when dissolved in water
–acidic solutions have a pH<7
bases
accept H+ when dissolved in water
—basic solutions have a pH>7
buffer systems
chemicals that can combine with/release H+ in order to keep the pH of a solution stable
pH scale
measures of H+ concentration in a solution
- change in 1 unit on scale means 10x the change in H+ concentration
- greater the H+ concentration, lower the pH number
diagram of the pH scale
0———7———14
- highest H+ and most acidic at zero
- neutral is at 7
- most basic and lowest H+ at 14
weak acids
reluctant H+ donors
ex. carbonic acid
strong acids
completely give up H+ when dissolved
ex. HCl
acid rain
pH5
-a lot comes from the sulfur dioxide; dissolves in water vapor
salts
compounds that release ions other than H+ and OH- when dissolved in water
