Making Sense of
the Periodic
Table
Trends and what they mean
adapted from:
http://www.amnh.org/ology/features/stufftodo_einstein/atommobile_read.php
http://www.middleschoolchemistry.com/multimedia/chapter4/lesson2
Watch this video
https://youtu.be/0RRVV4Diomg
Where does the “period” in periodic come from?
Based on where in the periodic table you are, you will see
different common properties
Based on where in the periodic table you are, you will see
different common properties
We will learn more about the chemical and physical
properties of these groups of elements and the
molecules they make later in the unit…
for now...back to individual elements.
This is a close
up of the first
20 elements
Many common
substances are
made from
these 20
elements
To understand how these 20 elements make many different
types of substances we must first understand their electrons.
Electrons are the key to making
compounds through covalent and
ionic bonds (more to come)
Electron “shells”
Electrons are in regions around the
nucleus that are different
distances away from the nucleus
The electrons surround the nucleus
in 3 dimensions bu it is easier to
show an energy level model in two
dimensions like the model that
looks like a target.
For example…
Take an Oxygen Atom
This energy level model shows two electrons on the first energy
level and six electrons on the second energy level
Since this atom has a total of eight electrons, it also has eight
protons
the atom with eight protons in its nucleus (atomic number 8) is
oxygen
Here’s
how that
looks for
the first
20
elements
Lewis Dot Structures
● Lewis Dot Structures are like simplified electron energy level model
● The lewis structure contains the element symbol with dots
representing electrons
● The only electrons shown are those on the outer energy level, which
are known as valence electrons
● The electrons are placed around the element symbol, one at a time,
clockwise or counterclockwise, and then grouped in pairs as more
electrons are needed
Finding the number of valence electrons
going across the periodic table, each group
has one more valence electron
except helium (which only has 2)
The number of valence electrons is incredibly
important to bonding