The Periodic Table
Periodic Table Groups to Know…
The Periodic Table
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The elements are arranged in rows and columns on
the Periodic Table according to the similarities in their
properties
Metals are found on the left side and bottom of the
Periodic Table
Non-metals are found on the right side of the Periodic
Table
The Periodic Table
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Metalloids are arranged in a diagonal pattern between the
metals and non-metals
The Periodic Table
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A column of elements is known as a GROUP
The group number corresponds to the number of
valence electrons
A horizontal row of elements is known as a PERIOD
The period number corresponds to the number of
shells containing electrons
The Periodic Table
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Four groups have characteristic family names :
Group I Alkali metals
Group II Alkaline earth metals
Group VII Halogens
Group VIII Noble (inert) gases
The Periodic Table
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The large block of elements between groups 2 and 3
forms a transition between the metals on the left and
non-metals on the right and are called the Transition
metals
Elements 58-71 are called Lanthanides (or rare earth
elements) because of their rare occurrence in nature
The Periodic Table
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Elements 90-103 are called Actinides and these are
all radioactive elements
Elements with atomic numbers more than 92 are
called transuranium elements. They are not found
in nature and are synthesised in the laboratory
Group I: Alkali metals
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Lithium (Li), Sodium (Na), Potassium (K), Rubidium
(Rb), Caesium (Cs) and Francium (Fr)
Each has one electron in the valence shell
Lose the one electron in chemical reactions to form
the M+ ion
Group I: Alkali metals
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Very reactive with water (stored under paraffin oil to
exclude moisture)
Form white crystalline solids which are soluble in water
Group II: Alkaline Earth metals
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Beryllium (Be), Magnesium (Mg), Calcium (Ca),
Strontium (Sr),
Barium (Ba),
Radium (Ra)
Each has two electrons in its valence shell
Lose 2 electrons to form M2+ ions in chemical
reactions
Group II: Alkaline Earth metals
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Less reactive with water than group I metals
From white crystalline solids, some of which are soluble
in water
Group IV
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Carbon is a non metal, Silicon and Germanium are
metalloids and Tin and Lead are metals
4 valence electrons
Carbon, silicon and germanium react to form compounds
of general formula XY4 where X is the group IV element
Tin and lead form +2 and +4 ions
Group VII: Halogens
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Exist as diatomic molecules: Fluorine F2 Chlorine Cl2
Bromine Br2 Iodine I2 Astatine At2
Are very reactive non metals
Occur in nature as the halide ions X- in salts when
reacted with metals (i.e. they have gained one
electron)
Group VIII: The Noble Gases
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Helium He Argon Ar
Neon Ne
Krypton Kr
Xenon Xe
Radon Rn
Are unreactive non metals due to their stable
electronic configuration
Do not usually form compounds (He and Ne do not
form compounds)
The Transition Elements
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Located between Group II and III
Have relatively high melting points and densities
Usually form coloured ions in solutions
Copper: blue
Iron(II): green
Iron(III): brown
Chromium: orange
Nickel: green
Trends in the Periodic Table
 Elements
within a group have the same
number and distribution of valence
electrons
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= some patterns/trends in behaviour
 Reactivity
 Atomic
Radius
 Electronegativity
Trend: Reactivity
 Most
reactive:
Alkali Metals  lose one electron to from an
octet
 Halogens  gain one electron to from an
octet
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Trend: Reactivity
Increasing
Increasing
Increasing
Increasing
Trend: Atomic Radius
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Atomic Radius = a measurement of the size of
an atom (radii = plural)
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Atomic radii increases as we move down a
group
More electron shells = bigger
 With each additional energy level the attractive
forces of the nucleus (protons, +) is reduced =
shielding effect
 Valence electrons (outer shell) are not as strongly
attracted = bigger radius
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Trend: Atomic Radius
 Atomic
radii decreases from left to right
across a period
Moving from left to right atoms have more
protons
 Attractive forces of the nucleus (+) for valence
electrons (-) increase
 Electrons pulled closer to the nucleus = smaller
radius
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Increasing
Increasing
Na
Mg
Al
Si
P
S
Cl
Ar
Trend: Electronegativity
 Electronegativity
= a number that
describes the ability of an atom to attract
electrons
 Provides a means of prediction the nature
of the forces that hold a pair of atoms
together in a bond
More electronegative = stronger pull on
electrons being shared
 Less electronegative = weaker pull on
electrons being shared
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Trend: Electronegativity
Increasing
Increasing
Atomic Radius & Electronegativity
Electronegativity increases when the atomic
radius is small
 Electronegativity decreases when the atomic
radius is large
 Large atomic radius = valence electrons are
further from the nucleus
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Less attractive forces holding the valence
electrons
 Less attractive forces to pull electrons to t he
atom
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