Chapter 15 –
Elements & The
Periodic Table
15.1 The Periodic Table of
the Elements– (pp. 334-340)
Periodic Table Timeline
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Lavoisier (1770-1789) Composed the first list of
33 elements. Distinguished metals from
nonmetals.
Berzelius (1828) Created a table of atomic
weights. Introduced idea of chemical symbols.
Dobereiner (1829) Developed triads-groups of 3
elements with similar properties.
Newlands (1864) Arranged known
elements in order of increasing atomic
weights. Proposed the Law of Octaves.
 Meyer (1869) Compiled a periodic table
with elements arranged by atomic
weight. Elements with similar properties
arranged in columns.
 Mendeleev (1869) Created a periodic
with elements arranged by atomic
weight. Elements with similar properties
arranged in columns.
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Ramsay (1894) Discovered noble
gases.
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Moseley (1914) Determined atomic
numbers of each element. Modified the
periodic law-an element’s properties
varies periodically with its atomic
numbers.
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Seaborg (1940) Synthesized elements
beyond uranium.
15.1 Physical properties
 Characteristics
that you can see through
direct observation are called physical
properties.
 Physical properties include color, texture,
density, brittleness, and state (solid, liquid,
or gas).
 Melting point, boiling point, and specific
heat are also physical properties.
15.1 Physical properties
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A physical change does not result in a
new substance being formed.
15.1 Chemical properties
 Properties
that can only be observed
when one substance changes into a
different substance are called chemical
properties.
 Any change that transforms one
substance into a different substance is
called a chemical change.
15.1 The Periodic Table
 The
periodic table organizes the elements
according to how they combine with other
elements (chemical properties).
 The periodic table is organized in order of
increasing atomic number.
15.1 The Periodic Table
 The
periodic table is
further divided into
periods and groups.
 Each horizontal row
is called a period.
 Each vertical column
is called a group or
family.
15.1 Atomic Number
Remember, the atomic number is the number
of protons all atoms of that element have in
their nuclei. This number does not change for
that element.
 If the atom is neutral, it will have the same
number of electrons as protons.
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15.1 Atomic Mass
The mass of individual atoms is so small
that the numbers are difficult to work with.
 To make calculations easier, scientists use
the atomic mass unit (amu).
 The atomic mass of any element is the
average mass (in amu) of an atom of each
element.
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15.1 Atomic Mass
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Atomic masses differ
from mass numbers
because most
elements in nature
contain more than
one isotope.
15.1 The Periodic Table
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All the elements in Group
1 of the periodic table
form similar compounds.
The metals lithium,
sodium, and potassium
all form compounds with
a ratio of 2 atoms of the
metal to 1 atom of
oxygen.
GROUPS 1 & 2
VERY REACTIVE METALS
Group 1 – The Alkali Metals
 The most reactive metals
1 electron in outer energy level
Other shared properties – soft, silver colored; shiny; low
density
Group 2 – The Alkaline Earth Metals
-very reactive, but less reactive than alkali metals
2 electrons in outer energy level
Other shared properties – silver colored; more dense than
alkali metals
THE TRANSITION METALS
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Groups 3-12
1 or 2 electrons in outer energy level
Less reactive than alkaline earth metals
Lanthanides and actinides are included in this
group
Other shared properties: shiny; good
conductors of thermal energy and electric
current; higher densities and melting points than
elements in Groups 1 & 2
LANTHANIDES
 They
follow the element
Lanthanum.
 Shiny, reactive metals
ACTINIDES
They follow the element Actinium
 All are radioactive. This means they are
unstable.
 Elements listed after Plutonium (element
94) do not occur in nature. They are man
made.
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GROUP 13
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Also known as the Boron Group
3 electrons in the outer energy level
Group contains Boron (a metalloid) and 4 metals
(Al - aluminum, Ga - gallium, In - indium & Tlthallium)
Reactive
Other shared properties: solid at room
temperature
GROUP 14
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Also known as the Carbon Group
4 electrons in outer energy level
Reactivity varies among the elements
Group contains 1 nonmetal (carbon), 2
metalloids (Si - silicon & Ge - Germanium) and 3
metals (Sn - tin, Pb - lead and Uuq)
Other shared properties: solid at room
temperature
GROUP 15
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Also known as the Nitrogen Group
Have 5 electrons in the outer energy level
Reactivity varies among the elements
Group contains 2 nonmetals (N - nitrogen & P phosphorus), 2 metalloids (As- Arsenic & Sb antimony) & 1 metal (Bi - bismuth)
Other shared properties: all but Nitrogen are
solid at room temperature
GROUP 16
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Also known as the Oxygen Group
Have 6 electrons in the outer energy level
Very reactive
Contains 3 nonmetals (O - oxygen, S - sulfur &
Se - selenium), 1 metalloid (Te - tellurium) & 2
metals (Po - polonium & Uuh)
Other shared properties: all but Oxygen are
solid at room temperature
GROUP 17
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Also known as the Halogens
Group contains all nonmetals (F - fluorine, Cl chlorine, Br - bromine, I – iodine & At - astatine)
Very reactive
There are 7 electrons in the outer energy level
Other shared properties: poor conductors of
electric current; react violently with alkali metals
to form salts; never found uncombined in nature.
GROUP 18
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Also known as the Noble Gases
Group contains all nonmetals (He - helium, Ne neon, Ar - argon, Kr - krypton, Xe - xenon, Rn –
radon & Uuo)
There are 8 electrons in the outer energy level
(He only has 2)
They are unreactive.
Other shared properties: colorless, odorless
gases at room temperature
HYDROGEN
Stands apart
 Only 1 electron in the outer energy level
 Very reactive
 Other properties: colorless, odorless gas
at room temperature; low density; reacts
explosively with oxygen.
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