Warm-Up: What do you know
about Chemistry?
 Draw and label an atom? (Hint: Proton, Neutron,
Electron, nucleus)
 Draw a water molecule? (Hint: Think of the chemical
formula!)
 Name 4 elements: ___________________
 Name 2 reasons chemistry is important to living
things…AKA BIOLOGY!
Welcome to BioChemistry!
The Chemistry of Life

Look out for the special check mark to
know which notes to write!
 On a checked slide with lots of notes, just write
underlined text!

Elements
 Fundamental forms of matter
 Each has only 1 type of atom
 Can’t be broken into simpler parts and keep their
unique properties
 92 elements occur naturally on Earth
 Watch the Elements SONG!

Most Common Elements in
Organic Molecules (CHNOPS)
Carbon
Hydrogen
Nitrogen
Oxygen
Also: Phosphorus and Sulfur
Also: Calcium and Potassium

Most abundant in
organic molecules
Most abundant in
Earth’s atmosphere

What Are Atoms?
 Smallest particles that retain
properties of an element
 Made up of subatomic
particles:
 Protons (+)
 Electrons (-)
 Neutrons (no charge)
 # Protons or Electrons=
Atomic Number
 # Protons + Neutrons=
Atomic Mass
Video: What does
an Atom really
look like?
A Peek at the Periodic Table
Which are the most common in
living things again?

Isotopes
 Atoms of an element with different numbers of
neutrons (different mass numbers, different weights!)
 Ex: Carbon 12 has 6 protons, ? neutrons
6
 Ex: Carbon 14 has 6 protons, ? neutrons
8

Radioactive Isotopes
have excess neutrons
 Radiation is mostly the extra neutrons that shoot out of
the nucleus!
 They can act as tracers because they show up on X-Ray
and radiation detectors
 Following tracers is useful in many areas of biology
Medical Uses of Radioactive
Elements
 Swallow Barium  helps Doctors see the large
intestines, which would not show on a normal x-ray.

What Determines How Atoms
Interact and Bond?
 The number and arrangement of their electrons
in the outer shell!
 Atoms are happy (stable) when their outer
shells are full
 1st Shell Full = 2 electrons
 2nd Shell Full = 8 electrons

Bonds, Molecules, Compounds
(Definitions)
 Bond = a union between electrons of atoms
 Molecule = two or more of the same type of atom (element)
bonded together. Ex: H2, N2, O2,
 Compound = two or more different types of atoms (elements)
bonded together. Ex: H2O

Ionic Bonding
 An exchange (one gives, the other accepts) of
electrons …
 An ion is a charged atom: it either lost electrons
(+), or gained electrons (-)
 If one atom loses electrons (+), and another atom
gains these electrons (-), then the charge
difference attracts the two ions to each other
Table Salt is the most famous example of an ionic bond!
 Sodium’s outer shell has one electron
NaCl
 Chlorine’s outer shell has seven electrons
 Na transfers electron to Cl forming Na+ and Cl Ions attract and remain together as NaCl

Covalent Bonding
• When atoms share a pair or pairs of electrons
to fill outermost shell
• A single covalent bond shares 1 pair of electrons.
• A double covalent bond shares 2 pairs of electrons.
• A triple covalent bond shares 3 pairs of electrons.

Hydrogen Bonding
 Hmm … To understand Hydrogen bonds, you
must first understand Polarity!
 A molecule is polar when electrons are not
shared equally, so …
 One part of the molecule is more positive and the
other part is more negative!

Hydrogen Bonding (cont’d)
 forms between the more “negative” atom in one polar
molecule … and … the more “positive” atom in another
such molecule.
 Usually, the more positive atom is Hydrogen.
 Forms between hydrogen and either nitrogen, oxygen or
fluorine
Other Examples of Hydrogen Bonds
one
large
molecule
another
large
molecule
a large
molecule
twisted
back
on
itself
Fig. 2.12, p. 27

Water is the classic example of
Hydrogen Bonding!
H
H
+
H+
_
O
+
+
+
+
H
_
O
Let’s Make M & M Isotopes!
Get Started
on your
Vocabulary!
Exit: What do you know about
Chemistry NOW?
 Draw and label an atom?
 Draw a water molecule?
 Label the polar ends
 Name 4 most common elements in living things: _______
 Describe what happens to the electrons in the following:
 Ionic Bonding:
 Covalent Bonding:
 Name 3 reasons chemistry is important to living
things…AKA BIOLOGY!
Welcome to BioChemistry!