Transcript Periodic Trends & the Periodic Table

Periodic Trends & the Periodic
Table
Periodic Table
• Periodic Table – arrangement of
elements in order of increasing atomic
number with elements having similar
properties in vertical columns
– Groups – vertical columns
– Periods – horizontal rows
Group Names
Group
1A
2A
6A
7A
8A
Name
Alkali Metals
Alkaline Earth Metals
Chalcogens
Halogens
Noble Gases
Groups
• Representative elements – group A
elements
• Transition elements – group B elements
Groups
• The group tell you the number of
valence electrons that the element has
• Valence electrons are electrons in the
outermost shell of the atom
• All group 1A elements have 1 valence
electron. Likewise, all group 8A
elements have 8 valence electrons.
Characteristics
• Elements in the same group exhibit
similar chemical characteristics due to
the fact that they all have the same
number of valence electrons.
• The most stable number of valence
electrons is 8
• This is called an octet
Charges
• Every element wants 8 valence electrons to become
stable. They will gain or lose valence electrons to
form an octet
• For example…Group 1A elements have 1 valence
electron. They can either gain 7 electrons to have an
octet or lose 1.
• What is easier?
Lose 1
• If an element loses 1 electron (1 negative charge)
what charge will the resulting ion have?
+1
Charges
• Let’s go to group 7A. This group has 7
valence electrons
• It can either loose 7 or gain 1
• What is the easiest?
Gain 1
• What will be the resulting charge if the
element gain 1 electron (1 negative charge)?
-1
Physical States and Classes of
the Elements
• The majority of the elements are metals.
They occupy the entire left side and
center of the periodic table.
• Nonmetals occupy the upper-right-hand
corner.
• Metalloids are located along the
boundary between metals and
nonmetals
Metals
• Metals are elements that have luster,
conduct heat and electricity, and
usually bend without breaking.
Transition Metals
• The elements in Groups 3 through 12 of
the periodic table are called the
transition elements.
• All transition elements are metals.
• Many transition metals can have more
than one charge
Inner Transition Metals
• In the periodic table, two series of elements,
atomic numbers 58-71 and 90-103, are
placed below the main body of the table.
• These elements are separated from the main
table because putting them in their proper
position would make the table very wide.
• The elements in these two series are known
as the inner transition elements.
Inner Transition Metals
• The first series of inner transition
elements is called the lanthanides
because they follow element number
57, lanthanum.
• The second series of inner transition
elements, the actinides, have atomic
numbers ranging from 90 (thorium, Th)
to 103 (lawrencium, Lr).
Non Metals
• Although the majority of the elements in the
periodic table are metals, many nonmetals
are abundant in nature
• Most nonmetals don’t conduct electricity,
are much poorer conductors of heat than
metals, and are brittle when solid.
• Many are gases at room temperature;
those that are solids lack the luster of
metals.
Properties of Metals and
Nonmetals
Metalloids
• Metalloids have some chemical and
physical properties of metals and other
properties of nonmetals.
• In the periodic table, the metalloids lie
along the border between metals and
nonmetals.
Electron Dot Structures
• An electron dot structure consists of the
elemental symbol surrounded by dots
which represent valence electrons
Examples
• Draw the electron dot structure for Na
• Draw the electron dot structure for Al
• Draw the electron dot structure for Br
Periodic Trends
• Periodic Trends are trends that occur
across the periodic table and down the
periodic table
• They include: atomic radius, Ionization
energy, electro negativity, metallic
character, and ionic radius
Atomic Radius
Decreases
Increases


• Atomic Radius – size of the atom
Ionization Energy
Increases
Decreases


• Ionization energy – the ability to pull
off 1 electron
Electro negativity
Increases
Decreases


• Electro negativity – the ability of an
atom to attract another atom
Metallic Character
Decreases
Increases


• Metallic character – how much like a
metal the element is
Ionic Radius
• When you talk about ionic radius, you
are comparing an atom and its ion
• When an atom has a negative charge,
you have added electrons
• Which makes it bigger
• For example, which will be larger:
• Cl or Cl-1
Ionic Radius
• When an atom has a positive charge,
you have taken away electrons
• Which makes it smaller
• For example, which will be larger:
• Na or Na+1