Download 2.1 Atoms, Ions, and Molecules

2.1 Atoms, Ions, and Molecules
KEY CONCEPT
All living things are based on atoms and their
interactions.
2.1 Atoms, Ions, and Molecules
What is biochemistry?
•Biochemistry is the study of structure,
composition (what things are made up
of), and chemical reactions that occur
in living things.
•Living things (biotic factors) depend
on chemistry for life…so biology and
chemistry are closely related!
2.1 Atoms, Ions, and Molecules
Living things consist of atoms of different elements.
• An atom is the smallest basic unit of matter.
• An element is one type of atom.
Hydrogen atom (H)
H
Oxygen atom (O)
O
2.1 Atoms, Ions, and Molecules
Elements
• Pure substances that
cannot be broken down
chemically into simpler
kinds of matter.
– Made of only 1 type of
atom
– A group of atoms of the
“same” type.
• More than 100 elements
(91 are naturally
occurring)
2.1 Atoms, Ions, and Molecules
Important Element Facts
• There are 25 elements
found in living things
• Trace elements are
present in very small
amounts, but necessary
for survival
• Four elements make up
96% of living things
-COHN
2.1 Atoms, Ions, and Molecules
Atomic Model
• An atom has a nucleus and electrons.
– The nucleus or central core has protons (+ charge ) and
neutrons (NO charge).
– Electrons (- charge) are in energy levels outside
nucleus.
Oxygen atom (O)
Nucleus:
8 protons (+)
8 neutrons
outermost energy
level:
6 electrons (-)
inner energy level:
2 electrons (-)
2.1 Atoms, Ions, and Molecules
Periodic Table
• Atomic Number - # of
protons
• Atomic Symbol –
Letters
– 1st capital
– 2nd lower case
• Atomic Mass - # of
protons and neutrons
2.1 Atoms, Ions, and Molecules
To find the number of neutrons, subtract the atomic mass
from the atomic number
For example:
• Atomic # = # of protons
# of protons = # of electrons
• Atomic mass = # of protons
and neutrons. To find
neutrons subtract atomic #
and atomic mass
2.1 Atoms, Ions, and Molecules
Draw the atomic structure of the following atoms:
2.1 Atoms, Ions, and Molecules
• A compound is made of atoms of different elements
bonded together.
• Smallest particle of a compound is a molecule
• Most elements exist as compounds
– water (H2O)
– carbon dioxide (CO2)
– many other carbon-based compounds in living things
2.1 Atoms, Ions, and Molecules
Molecules
•Is two or more atoms
held together by
covalent bonds.
•Are the simplest part
of a substance that
retains all of the
properties of the
substance and exists
in a free state.
•Some molecules are
large and complex.
2.1 Atoms, Ions, and Molecules
Ions
• An ion is an atom that has gained or lost one or more
electrons.
• Ionic bonds form because atoms are more stable if the
outermost energy level is full
– positive ions
– negative ions
• Ionic bonds form between oppositely charged ions
gained electron
Na loses an
electron to CI
Sodium atom (Na)
Chlorine atom (CI)
ionic bond
Sodium ion (Na+)
Chloride ion (CI-)
2.1 Atoms, Ions, and Molecules
Covalent bonds.
• A covalent bond forms when atoms share a pair of
electrons.
• Very Strong bond
– multiple covalent bonds
– diatomic molecules
covalent bonds
Oxygen atom (O)
Carbon atom (C)
Carbon dioxide (CO2 )
Oxygen atom (O)