Unit 3 - Periodic Table (Chapters 6 and 7)
DMITRI MENDELLEV (Russian, 1834-1907)

Arranged the known elements in order of increasing atomic mass

Noticed a repeating pattern in the properties of the elements

Designed a table with rows and columns to show the repeating pattern

Left blank spaces in the table to represent elements not known in his time

Predicted the chemical properties of those elements
MODERN PERIODIC TABLE
Henry Moseley (British, 1887-1915) determined the nuclear charge, also called the atomic number,
of the atoms of the elements
 Arranged the elements in a table by order of atomic number
 Elements are still arranged by increasing atomic numbers today
 “periodic” name given because of the similar properties that repeat every so many elements
The periodic law:
When the elements are arranged in order of increasing atomic number, there is a periodic pattern
in their physical and chemical properties.

Table is arranged in columns (groups or families) and rows (periods)
Groups

Each vertical column is called a group or family

18 groups, numbered 1 to 18

Groups 1,2 and 13-18 are called main-group, or representative elements. They are also
labeled IA, IIA and IIIA-VIIIA respectively.

Groups 3-12 are called transition metals
Note: the IUPAC (International Union of Applied Chemistry) suggested the numbering 1-18 in
order to avoid confusion. The Roman numerals and As and Bs explained above are used in North
America, but most tables show both conventions.

Elements in each group resemble each other; they react in similar ways to other substances
Elements in the same group are similar because they have the same number of electrons
in the outer shell (valence electrons).

Groups reflect the number of electrons in the outer shell (valence electrons).

Group 1(IA) has 1 valence electron, Group 2 (IIA) and the Bs (Groups 3-12) have 2 valence
electrons, Group 13 (IIIA) has 3 valence electrons, Group 14 (IVA) has 4 valence electrons, Group 15
(VA) has 5 valence electrons, Group 16 (VIA) has 6 valence electrons, Group 17 (VIIA) has 7 valence
electrons, and Group 18 (VIIIA) has 8 valence electrons, except Helium which has 2 valence electrons.

Lewis Dot Notation – way to represent the number of valence electrons using the element
symbol and “dots” to represent the valence electrons
Oxidation number – the number of electrons an atom gains, loses or shares when it forms
chemical bonds.
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Group Names
1 – Alkali metals
2 – Alkaline earth metals
3-12 – Transition metals
13 – Boron group
14 – Carbon group
15 – Nitrogen group
16 – Oxygen group
17 – Halogen family
18 – Noble gases
Hydrogen is in a group by itself.
Group 1 (IA) Alkali metals
1. most reactive of all metals
2. Softer and less dense than other metals (can be cut with a knife)
3. never found as free elements – too reactive
4. when pure, stored in oil
5. react violently with water
6. identified by flame test
7. one valence electron is lost to form a positive ion
Group 2 (IIA) Alkaline earth metals
1.
harder and denser than alkali metals
2.
highly reactive
3.
not found free in nature – too reactive
4.
two valence elect
Groups 3-12 Transition metals
1. less reactive than groups 1 or 2
2. some are brittle
3. many have more than one oxidation number
4. most have high melting points and are hard
5. form brightly colored compounds
Group 13 (IIIA) – Boron Family
1. Boron – metalloid, hard, brittle, not found free
2. Aluminum – light , strong, corrosion-resistant metal
3. Gallium – metal, used in thermometers
Group 14 (IVA) – Carbon family
1. Carbon – all living things contain carbon, most compounds that contain carbon
are called organic compounds, diamond and graphite are two forms of carbon
2. Silicon – used to make glass and cement, used in transistor technology, photocells
3. Germanium – also used in transistors
4. Tin – metal that resists rusting and corrosion, used to “tinplate” an iron can, plumber’s
solder
5. Lead – Dense metal, poisonous
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up 15 (VA) – Nitrogen family
1. Nitrogen - most abundant element in earth’s atmosphere, does not combine easily
with other elements, used in production of fertilizer, explosives, drugs and dyes,
essential to living organisms.
2. Phosphorus – used to make tips of matches
3. Arsenic – insecticides
up 16 (VIA) – Oxygen family
1. Oxygen – most abundant element, 20% of air, 60% by mass of human body, 50% by mass
of Earth’s crust(combined with silicate rocks), produced by plants, used in medicine
2. Sulfur – used to manufacture drugs, matches and gunpowder
3. Selenium – used to make red glass and enamels, used in light-sensitive switches
4. Tellurium – used to make alloys
5. Polonium – very rare radioactive element
Group 17 (VIIA) Halogens
1. Most active nonmetals
2. tend to gain electrons to form negative ions
3. never found free in nature
4. low melting and boiling points
5. as gases, exist as diatomic elements
6. combine with metals to form salts
Group 18 (VIIIA) Noble Gases
1. inert
2. found in small amounts in the atmosphere
Periods
Each horizontal row is called a period
7 periods, numbered 1 to 7
▪ Periods correspond to energy level, n
▪ Rows 6 and 7 are too long to fit in the table, so part of them are placed at the bottom of the table.
The two rows at the bottom of the table are called the inner-transition metals. The first row is
called the lanthanide series and the second row is called the actinide series.
▪ Atomic numbers increase along each row
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METALS, NONMETALS AND METALLOIDS

A stairstep line on the periodic table separates metals from nonmetals

Metals are to the left of the stairstep line

Nonmetals are to the right of the stairstep line

Properties of Metals
1.
good conductors of heat and electricity
2.
shiny
3.
have high melting points
4.
ductile
5.
malleable
6.
tend to lose electrons
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Properties of Nonmetals
1.
2.
3.
4.
5.


poor conductors of heat and electricity
dull
have low melting point
solids are brittle
tend to gain electrons
Properties of Metalloids
All elements on either side of the stairstep line EXCEPT Aluminum
They have properties of both metals and non metals
1.
white or gray in color
2.
conduct heat and electricity but not as well as metals
3.
ductile
4.
malleable
5.
not as shiny as metals
6.
solids
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