Atomic Theory and the
Periodic Table Day 6 &
7
Boon Chemistry 08.19_21.13
Homework Review: p. 122 #6, 7, 11, 12
6. What do elements in the same period have in
common? A: They have the same number of
energy levels with electrons in them.
For example, the
period 2 elements
have electrons in the
1st and 2nd energy
levels.
Homework Review: p. 122 #6, 7, 11, 12
7. What do elements in the same group have in
common? A: They have the same number of
valence electrons.
For example, the
group 1elements
have 1 valence
electron.
Homework Review: p. 122 #6, 7, 11, 12
11. What determines the number of elements found in
each period in the periodic table? A: The number of
available electron orbitals in each energy level
determines the number of elements in a period.
Homework Review: p. 122 #6, 7, 11, 12
12. Are elements with similar chemical properties more
likely to be found in the same period or in the same
group? A: The same group because the number of
valence electrons determine the chemical properties.
For example, the
alkaline earth metals
all have 2 valence
electrons so they
form ionic bonds with
Fluorine in the
proportion: XF2
Periodic Trends Lab: Introductory Video
 As you watch, think about the following:
 Mendeleev put together his periodic table
in the 1860s. What was known about
atoms at that time?
 What properties did Mendeleev use to
categorize and order the elements?
Periodic Trends Lab: Introduction
 A trend is a predictable change in a certain direction.
Understanding periodic trends allows us to make predictions
about the chemical behavior of the elements.
Example: Metallic properties of elements decrease from left to right across the table.
Periodic Trends Lab: Introduction
 In this investigation, your lab group will recreate Dimitri Mendeleev’s discovery of the
classification of the elements and the
periodic law using a deck of special
element cards. The real properties of the
elements, but not their names or symbols,
are written on these cards. As the cards
are arranged and rearranged based on
logical trends in some of these properties,
the nature of the periodic law should reveal
itself.
Pre-Lab Notes: Vocabulary
Atomic Radius: The distance from the nucleus to the
Valence electrons. Units: picometers (pm) (1 pm = 10-12 m)
•Note: determined by measuring the distance between nuclei and
dividing by two.
ATOMIC SIZE/RADIUS


The more energy levels (bigger period number) the
bigger the atom
The more protons an element has the more the
electrons are pulled toward the nucleus, making the
atom smaller
Pre-Lab Notes: Vocabulary
Ionization Energy: The energy required to take An
electron away from an atom. Units: kilocalories per mole
(kCal/mol).
Atoms that want to gain electrons have
high ionization energies.
Atoms that want to lose electrons have
low ionization energies.
Noble gases have the highest
ionization energy.
Pre-Lab Notes: Vocabulary
Electronegativity: A measure of an atom’s tendency to
attract electrons towards itself. Units: none, scale of 0-4
with Fluorine at 4 (highest).
Here, Cl is more
Atoms that want to gain electrons have
high electronegativity.
Atoms that want to lose electrons have
low electronegativity.
Noble gases have no electronegativity.
electronegative than H. Cl pulls
more electrons towards it.