Chemistry of Life
Chapter 2
Warm Up 8/20
Try to recall the following information
without referencing your textbook or a
friend
What is an atom?
What is an element?
What differentiates one element from
another?
What are protons, neutrons and
electrons?
Answers
Atom: basic unit of matter
Made up of 3 smaller particles
Neutrons- no charge “neutral.” Found in nucleus
Protons- positive charge. Found in nucleus
Electrons- negative charge. Tiny. Orbit nucleus in
a 3D “electron cloud”
Element: a specific kind of atom
Determined by number of PROTONS
Examples?
Element name
Atomic
Number
Element
Symbol
Atomic Mass
Atomic Number and Atomic
mass
Atomic Number
Number of protons in that element
Neutral atoms also have that same number
of electrons
Atomic mass
Mass of protons and neutrons
*usually about double the atomic number
because there are typically the same number
of protons and neutrons
Bohr’s Atomic Model
Nucleus in center (protons and
neutrons)
Electrons are in energy levels/energy
shells surrounding the nucleus
Energy level 1 holds up to 2 electrons
Energy level 2 holds up to 8 electrons
Energy level 3 holds up to 18 electrons
Stability and Octet Rule
An atom is stable if its outer shell is full OR
has eight electrons (octet rule)
The outer shell is known as the VALENCE shell
The number of electrons in the valence shell
determines the reactiveness of the the
element
The closer to stable, the more reactive
If the shell is full, the atom is non-reactive
Noble gases
Let’s draw some atoms
*list the number of valence electrons for each
Hydrogen
Helium
Oxygen
Neon
Magnesium
Unstable Atoms “like” to
form bonds to become stable
Ionic bonds
Covalent bonds
Warm Up 8/20
Draw a fluorine atom
How many valence electrons does it
have?
What does that say about its reactivity?
Draw a fluorine ion
How many valence electrons does it
have?
What does that say about its reactivity?
Today 8/22
Review ions
Atoms that have gained/lost electrons
Example: sodium ion
Learn about ionic bonding
Example: lithium chloride
Ionic Bonds
Attraction between oppositely charged
ions
Covalent Bonds
Sharing of valence electrons