The Chemical Context of Life
Date _____________________
_______________ Anything that takes up space and has mass.
_______________ A substance that cannot be broken down into other substances by
chemical reactions.
_______________ A combination of two or more elements in a fixed ratio.
_______% of living matter is made up of Carbon (
and Nitrogen (
)
), Oxygen (
), Hydrogen (
)
_________________________ those elements required by an organism in small
quantities
 Deficiencies in trace elements can cause illness. For example the lack of iron can
cause anemia and the lack of iodine can cause a goiter.
Atomic structure determines the behavior of an element.
Atoms – fundamental unit of matter. The
smallest possible amount of an element that
retains the element’s properties.
Three types of subatomic particles are relevant
to our understanding of the chemistry of life.
These particles are the proton, the neutron
and the electron.
_______________
 Located in the nucleus
 Charge of +1
 Mass of 1 dalton
_______________
 Located in the nucleus
 Charge of 0
 Mass of 1 dalton
_____________________ the same as the
number of protons in the nucleus; determines
the element
_____________________ sum of the protons
and neutrons in the nucleus of an atom
_____________________ since protons and
neutrons have a mass close to 1 dalton, the
mass number tells us the approximate mass
of the whole atom.
_______________
 Located in a cloud around the nucleus
 Charge of -1
 Mass is negligible
Isotopes
Isotopes have the same number of
___________ and ____________, but
different numbers of ____________
Radioactive Isotopes
 Can cause mutations in DNA
 Useful in medical research and
medicine as tracers
Electron Orbital – the three dimensional space where an electron is found 90% of the
time.
Electron configuration and chemical properties
The chemical properties of an atom depends mostly on the number of electrons in its
outermost shell.
____________________ - electrons in the outermost shell
____________________- outermost energy shell
Chemical Bonding
 When atoms with incomplete outer shells react, each atom gives up or acquires
electrons so that partners end up with completed valence shells.
 Atoms do this by either sharing (______________________________) or
transferring outer electrons (_____________________________)
 The strongest chemical bonds are covalent bond and ionic bonds
_________________ bond – two
atoms sharing one or more pairs of
outer shell electrons.
_________________ two or more
atoms held together by covalent
bonds.
The number of single covalent bonds an atom can form is equal to the number of
additional electrons needed to fill its outer shell.
____________________________ sharing of 2 pairs of electrons
____________________________ at atom’s attraction for the shared electrons of the
bond. The more electronegative an atom, the more strongly it pulls atoms towards
itself.
Polar vs. Non-Polar Covalent Bonds
________________ Bond –
attraction between ions of opposite
charge
__________ -- atom or molecule
with an electrical charge resulting
from the gain or loss of one or
more electrons.
Anion = ion with a __________________ charge
Cation = ion with a __________________ charge
Weak Chemical Bonds
Weak bonds, unlike covalent bond, allow interactions between molecules to be brief
The most important weak bond in living matter is the hydrogen bond.
Hydrogen Bond = occurs when a hydrogen atom covalently bonded to one
electronegative atom is also attracted by another electronegative atom. In living cells,
the electronegative partner involved is usually a nitrogen or oxygen atom.