Elements & The Periodic Table
Forces within an atom…

1) Electromagnetic force
 Opposite
 protons
 Like
charges attract
(+) attract electrons (-)
charges repel
 protons
(+) repel protons (+)
 electrons (-) repel electrons (-)
 This holds the electrons in their energy
levels
Forces within an atom…

2) Strong force
 Cancels


out the electromagnetic force
Holds the protons together along with the neutrons
in the nucleus
The attraction between the particles that make up the
protons and neutrons (quarks) are stronger than the
force of repulsion
(like 2 body builders playing tug of war)


Only works when the particles are close enough
together
The neutrons help to separate the protons from each
other so that they do not feel as strong of a repulsive
electromagnetic force
http://www.youtube.com/watch?v=UkLkiXiOCWU
Periodic Table

The Periodic Table was “invented” by
Dmitri Mendeleev around 1870
 At the time there were only about 65 elements
discovered
 Multiple chemists had determined the properties of
these elements (i.e. relative masses, chemical
activity, physical properties) but there was no
systematic way of organizing the elements
Periodic Law

Mendeleev noticed that certain groups of elements
had similar properties
He found that when he listed the elements in order
of increasing relative mass those similar
properties reoccurred in a pattern

Periodic Law:


When elements are arranged in order of increasing
relative mass, certain sets of properties recur
periodically
The First Periodic Table

Mendeleev organized elements in a table



Mass increased from left to right
Elements with similar properties in same
vertical columns
He was able to predict properties of elements
that had not been discovered yet
The Modern Periodic Table

Elements are listed in order of increasing
atomic number (not relative mass like Mendeleev’s)

Elements are still grouped according to
common properties
Location of Metals, Non-Metals, Metalloids

The Periodic Table is split by the “stair-step” line

On your Periodic Table:
Draw in the stair-step line
Location of Metals, Non-Metals, Metalloids, & Transition Elements





Metals are located on the LEFT of the stair-step
line
Non-Metals are located on the RIGHT of the stairstep line
Metalloids are located next to the stair-step line
(B, Si, Ge, As, Sb, Te, At)
Transition Elements are located in the SHORT
columns
On your Periodic Table:
Write in Metals, Transition Elements, Metalloids, and
Non-Metals on the top next to each section
Properties of Metals

Physical Properties
Have luster (shininess)
 Conduct heat and electricity
 Ductile (can be made into wires)
 Malleable (can be hammered into sheets)


Chemical Properties
Tend to be electron donors (lose electrons)
 Many corrode (react with water or air)
 Precious metals (gold and silver) are not very reactive

Properties of Non-Metals

Physical Properties
Generally the opposite of metals
 May be solid, liquid or gas at room temperature
 Have much lower densities and melting points than
metals


Chemical Properties
Tend to be electron acceptors (gain electrons)
 Noble Gases (Group 18) do not react with other
elements

Properties of Metalloids

Metalloids have properties of both metals
and non-metals
Properties of Transition Elements

Transition elements are located in the short
columns (#3-12)

Properties are more difficult to predict

Number of valence electrons can vary because
the electrons shift or “transition” from one energy
level to the other
Properties of Rare Earth Elements

Rare Earth Elements are the 2 “removed” rows
(on the bottom of your Periodic Table)

These rows fit between Lanthanum (La # 57) and
Hafnium (Hf #72) and Actinium (Ac#89) and
Rutherfordium (Rf#104)
Many of these are man-made elements


The bottom row (#90-#103) are called the
Actinoids- these are all radioactive
Groups on the Periodic Table

Elements are listed in groups (families)

Groups are represented in each vertical
column (up and down)
Patterns within a Group
1) All elements in the group have the same number of
valence electrons (in the tall columns) and therefore
the same charge (we’ll talk more about this during bonding)
 Valence electrons are the electrons in the
outermost electron energy level
 On your Periodic Table:
Number each column (1-18)
*Your book numbers each tall column with an A after the number and
each short column with a B after the number
*Note: The transition metals (short columns) do not
necessarily follow these rules, but the elements in the tall
columns do!
Patterns within a Group: METALS
2) Metals become MORE reactive as you
move DOWN a group and the ATOMS
become LARGER (top to bottom)

The larger an atom is, the further those valence electrons
are from the nucleus, and the easier it is to remove those
valence electrons
Patterns within a Group: NON-METALS
3) Non-Metals become LESS reactive as you
move DOWN a group and the ATOMS
become LARGER (top to bottom)

Non-metals tend to GAIN electrons when they undergo
chemical changes so it becomes more difficult to gain
electrons when the atom is larger because the
electromagnetic force is not as strong the further you get
from the nucleus
Main-Group Elements

Elements in the tall columns (1,2, 13-18)

Group 1: Alkali metals


Group 2: Alkaline Earth metals


most reactive non-metals
Group 18: Noble Gases


fairly reactive, but not as much as alkali metals
Group 17: Halogens


very reactive, especially with water!
non-reactive (have full valence shells)
Other Main Groups:

named according to element at the top of their column
Periods on the Periodic Table

Elements are also listed in periods

Periods are represented in each horizontal
row (left to right)
Patterns within a Period



1) All of the elements within the same period
contain the same number of electron energy
levels
2) Elements become LESS metallic as you move
from left to right
3) Atom size DECREASES as you move left to
right


As you move left, the electromagnetic force increases between
the protons and electrons, pulling the energy levels in “tighter”
On your Periodic Table:

Number the Periods 1-7
More Reactive
More Reactive
http://www.chem1.com/acad/webtext/atoms/atpt-6.html
Noble Gases Group- Not Reactive