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Chapter: The Periodic Table
Table of Contents
Section 1: Introduction to the
Periodic Table
What does periodic mean?
• Periodic means with a repeating
pattern
• A periodic event is predictable
Periodic Table
**Periodic Table is a table that shows all the
chemical elements that have been
discovered.
**The elements in the P.T. are arranged
according to their properties, in a repeating
pattern.
**This means that their properties can be
predicted, according to their position in the
P.T.
• https://www.youtube.com/watch?v=fPnw
BITSmgU
• The genius of Mendeleev's periodic
table
https://www.youtube.com/watch?v=oylT
OhzpJL4
• Mendeleev and The Modern Periodic
Table
Mendeleev
• Russian chemist that publish a version
of a P.T. in which the elements were
arranged according to their atomic
mass.
• He observed that this arrangement
revealed a pattern.
Importance of Mendeleev’s work:
The importance of Mendeleev’s work lies on the
periodic table repeating patterns that he
observed and described.
By analyzing the properties of different
elements already present in the PT, he could
infer the properties of elements that were not
discovered yet.
With time, these “missing” elements were
discovered and placed in the PT empty spots.
The repeating patterns allow scientists to:
1)make predictions about an element’s
chemical and physical properties, based on
this element’s position on the periodic table.
(Elements with similar properties are placed in
the same area of the periodic table)
1)Find the correct location of a new element
in the periodic table.
• Henry Moseley an English physicist realized that Mendeleev's table could be improved by arranging the elements according to atomic number ( number of protons in the nucleus of an atom) rather than atomic mass
• That’ how the Periodic Table is organized today
Atomic Mass X Atomic Number
A period is a row of elements in the periodic table whose properties change gradually and predictably.
Why????
Because the atomic number increases by one, when you move from one element to another.
There are seven periods
The organization of the PT - Textbook page 436
• The periodic table has 18 columns of elements and each one is called a group or family.
• The groups or families are the columns. A group contains elements that have similar physical or chemical properties.
Today’s Periodic table :
textbook page 435 – Zones on the
Periodic table
• PT is divided in different zones:
Representative Elements – Gr 1,2, 13 through
18
Transition Elements – Gr 3 through 12
Inner Transition Elements – Two rows placed
below
Each element has an element key
• Name of the element, symbol, atomic number, atomic mass, the state of matter (at room temperature), if they are synthetic or not.
• the color of the box will tell you the type of element ( metals, metalloids and nonmetals)
The Element Keys
Metals – nonmetals and Metalloids
in the PT – read page 438
Atoms X Elements
•Atoms are the building blocks of matter
•Atoms form elements (elements have one
type of atom only)
***Atoms have chemical and physical
properties that will be kept by the
elements
Properties of Atoms and the pattern or
trends in the periodic table
• The chemical and physical properties of
atoms change according to the
location of the atom in the periodic
table
• Some of the properties are: ionization
energy, electronegativity, reactivity,
atomic radius, melting and boiling
point…
Atomic radius – distance from the center
of the nucleus to the last energy level of
the electron cloud
Atomic radius = the size of the atom
Graphs will reflect the PT trend- GROUP 1 atomic
number increases and the radius increases
Properties of Atoms: Atomic Radius
The atomic radius = the size of the atom.
Atoms generally get smaller as you go across the periods
Graphs – reflect the PT trend - PERIOD 4
Atomic Number increases but radius decreases
How can we explain that the radius of the
atoms decreases, when the atomic
number increases?
We would imagine that the more electrons
an atom has, the bigger the radius would
be.
Explanation: open book page 467 – Models of
atoms
Look at Group 1: Atomic Number increases and
radius increases – number of electrons increases
but the electrons are not as packet – there is
more space that the atoms can occupy without
being packet. (more energy levels to fit the
electrons)
The circles represent energy levels - the area
where you find electrons
Explanation: open book page 467 – Models of
atoms
Period: Atomic number increases and radius
decreases
- number of electrons increases with the atomic
number, but the space available for the
electrons is the same ( 2 energy levels)
Ionization Energy
An ion is an atom that lost or received an
electron.
Ionization energy is also a property of the
atoms and shows a pattern in the P.T.
Properties of Atoms: Ionization Energy
• Ionization energy is the energy required
to remove an electron from an atom in
the gas state of matter, to form a
positive ion
• The higher the ionization energy,
the more difficult it is to remove an
electron, because the atom is very
stable.
Ionization Energy - Group 1
Ionization Energy- Period 4
Usually metals have high melting and boiling
points because the atoms are united by
strong bonds.
Reactivity
• It is another property and it is the capacity
of an atom, to react with another atom.
• Fluorine is the most reactive non-metal
• Francium is the most reactive of the
metals
• Helium is the least reactive element
• You can notice a pattern of reactivity in
the PT
Reactivity of Elements
Reactivity
• Why does the reactivity go UP when you
move down in Groups 1 and 2 (metals)
of the PT?
Reactivity of Group 1- alkali metals
Electrons are found
in the energy levels
of the atoms.
Lithium has 2
energy levels,
Sodium 3 and
Potassium 4.
Reactivity of Group 1- alkali metals
Going down the group
the reactivity increases
because:
-The atoms are bigger
and there are more
energy levels
- the electrons in the
outer energy level are
less attracted by the
positive nucleus and will
react easily when
compared to the ones
closer to the nucleus
Reactivity and
Electronegativity
• The elements that are very reactive,
also have a high electronegativity.
What is electronegativity?
IMPORTANT
When atoms combine forming molecules,
they can share, donate or receive
electrons, forming chemical bonds.
Electronegativity is another property
• It is the tendency of an atom to attract
the electrons of a bond when this atom
is in a molecule. Ex:
• The chlorine atom has a higher
electronegativity than the hydrogen atom, so
the bonding electrons will be closer to the Cl
than to the H in the molecule.
From left to right: atoms in a period have more
protons, so the + charge in the nucleus is stronger,
attracting more the electrons that will tend to stay
closer to the nucleus.