just the basics, please!
Why study chemistry in a biology class?
All energy comes from chemical reactions…
therefore we carry out chemical reactions in our bodies constantly.
Life is all about
Starting with the periodic table – a very organized way of displaying all of the elements.
You can tell a lot about an element by looking at where it sits on the periodic table.
made up of only one type of atom.
has more than one atom.
An element can be a molecule (O2).
Compound: has more than one type of atom.
H2O is a molecule and a compound.
A compound will always have the same ratio of atoms for a particular compound.
that is, water will always be one oxygen and two hydrogen atoms. Once atoms
become a compound, it requires a chemical reaction to get those compounds back
a substance from which you can reacquire the original compounds
from the mixture with no chemical reaction; no set ratios (salt water could be 10%
salt, or 1.3% salt, but it’s still salt water either way)
118 elements, but only 3 (C, H, O) make up 98% of the earth.
Humans are mostly made
of 4 elements:
C, O, H, and N, with Ca and P coming in next in amount.
important elements in the body are Na, K and Cl.
(All of these are elemental symbols
you should be able to recognize and identify)
What is an atom?
The smallest unit that can be defined as a particular substance… a C
atom is the smallest unit of carbon… anything smaller is no longer carbon.
Atoms made up of three smaller particles: neutrons (no charge), protons (positive
charge), electrons (negative charge).
In an atom with a neutral charge, the # of protons
and electrons should be balanced (8+ and 8- is neutral).
The atom generally has the “planetary model” shape… with a “sun” made of protons and
neutrons, and “planets” circling are electrons.
The proton is the particle that gives an atom its identity – element 1, hydrogen, has one
proton (and because it is a neutral atom, also has one electron).
Element 2, helium, has 2 protons and 2 e-.
As long as an atom contains the same number of protons its identity will remain – so that
helium atom will always be helium as long as it has 2 protons… it gains a proton and
becomes Li… loses one, becomes H.
An atom can, however, have a variable number of neutrons – usually the # is near the # of
protons, but not always exactly the same.
Protons and neutrons together make up the
of an atom (the mass of e- is negligible).
Isotopes – atoms of a particular element
containing differing numbers of neutrons.
For example C-12, 6 protons/6 neutrons
(6+6=12): C-13, 6/7; C-14, 6/8.
Naturally occurring carbon is a mixture of these three