Elements may be categorized according to element families. Knowing how to identify families, which elements are included, and their properties helps predict behavior of unknown elements and their chemical reactions.
An element family is a set of elements sharing common properties. Elements are classified into families because the three main categories of elements (metals, nonmetals and semimetals) are very broad. The characteristics of the elements in these families is determined primarily by the number of electrons in the outer energy shell. Element groups, on the other hand, are collections of elements categorized according to similar properties. Because element properties are largely determined by the behavior of valence electrons, families and groups may be one and the same. However, there are different ways of categorizing elements into families. Many chemists and chemistry textbooks recognize five main families:
5 Element Families
Alkali metals
Alkaline earth metals
Transition metals
Halogens
Noble gases
9 Element Families
Another common method of categorization recognizes nine element families:
Transition Metals - Groups 3-12 - d and f block metals have 2 valence electrons
Boron Group or Earth Metals - Group 13 (IIIA) - 3 valence electrons
Carbon Group or Tetrels - Group 14 (IVA) - 4 valence electrons
Nitrogen Group or Pnictogens - Group 15 (VA) - 5 valence electrons
Oxygen Group or Chalcogens - Group 16 (VIA) - 6 valence electrons
Halogens - Group 17 (VIIA) - 7 valence electrons
Noble Gases - Group 18 (VIIIA) - 8 valence electrons
Recognizing Families on the Periodic Table
Columns of the periodic table typically mark groups or families. Three systems have been used to number families and groups:
The older IUPAC system used Roman numerals together with letters to distinguish between the left (A) and right (B) side of the periodic table.
The CAS system used letter to differentiate main group (A) and transition (B) elements.
The modern IUPAC system uses Arabic numbers 1-18, simply numbering the columns of the periodic table from left to right.
Many periodic tables include both Roman and Arabic numbers. The Arabic numbering system is the most widely accepted method used today.
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Alkali Metals or Group 1 Family of Elements
The highlighted elements of the periodic table belong to the alkali metal element family.
Todd Helmenstine
The alkali metals are recognized as a group and family of elements. These elements are metals. Sodium and potassium are examples of elements in this family.
Group 1 or IA
Alkali Metals
1 valence electron
soft metallic solids
shiny, lustrous
high thermal and electrical conductivity
low densities, increasing with atomic mass
relatively low melting points, decreasing with atomic mass
vigorous exothermic reaction with water to produce hydrogen gas and an alkali metal hydroxide solution
ionize to lose their electron, so the ion has a +1 charge
Hydrogen is not considered an alkali metal because the gas does not exhibit the typical properties of the group. However, under the right conditions of temperature and pressure, hydrogen can be an alkali metal.
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Alkaline Earth Metals or Group 2 Family of Elements
The highlighted elements of this periodic table belong to the alkaline earth element family.
Todd Helmenstine
The alkaline earth metals or simply alkaline earths are recognized as an important group and family of elements. These elements are metals. Examples include calcium and magnesium.
Group 2 or IIA
Alkaline Earth Metals (Alkaline Earths)
2 valence electrons
metallic solids, harder than the alkali metals
shiny, lustrous, oxidize easily
high thermal and electrical conductivity
more dense than the alkali metals
higher melting points than alkali metals
exothermic reaction with water, increasing as you move down the group. Beryllium does not react with water; magnesium only reacts with steam.
ionize to lose their valence electrons, so the ion has a +2 charge
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Transition Metals Element Family
The highlighted elements of this periodic table belong to the transition metal element family. The lanthanide and actinide series below the body of the periodic table are transition metals, too.
Todd Helmenstine
The largest family of elements consist of transition metals. The center of the periodic table contains the transition metals, plus the two rows below the body of the table (lanthanides and actinides) are special transition metals.
Groups 3-12
Transition Metals or Transition Elements
The d and f block metals have 2 valence electrons
hard metallic solids
shiny, lustrous
high thermal and electrical conductivity
dense
high melting points
These large atoms exhibit a range of oxidation states.
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Boron Group or Earth Metal Family of Elements
These are the elements belonging to the boron family.
Todd Helmenstine
The boron group or earth metal family is not as well-known as some of the other element families.
Group 13 or IIIA
Boron Group or Earth Metals
3 valence electrons
diverse properties, intermediate between those of metals and nonmetals
best known member of this group is aluminum
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Carbon Group or Tetrels Family of Elements
The highlighted elements belong the carbon family of elements. These elements are collectively known as the tetrels.
Todd Helmenstine
The carbon group is made up of elements called tetrels, which refers to their ability to carry a charge of 4.
Group 14 or IVA
Carbon Group or Tetrels
4 valence electrons
diverse properties, intermediate between those of metals and nonmetals
best known member of this group is carbon, which commonly forms 4 bonds
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Nitrogen Group or Pnictogens Family of Elements
The highlighted elements belong to the nitrogen family. These elements are collectively known as pnictogens.
Todd Helmenstine
The pnictogens or nitrogen group is a significant element family.
Group 15 or VA
Nitrogen Group or Pnictogens
5 valence electrons
diverse properties, intermediate between those of metals and nonmetals
best known member of this group is nitrogen
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Oxygen Group or Chalcogens Family of Elements
The highlighted elements belong to the oxygen family. These elements are called chalcogens.
Todd Helmenstine
The chalcogens family is also known as the oxygen group.
Group 16 or VIA
Oxygen Group or Chalcogens
6 valence electrons
diverse properties, changing from nonmetallic to metallic as you move down the family
best known member of this group is oxygen
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Halogen Family of Elements
The highlighted elements of this periodic table belong to the halogen element family.
Todd Helmenstine
The halogen family is a group of reactive nonmetals.
Group 17 or VIIA
Halogens
7 valence electrons
reactive nonmetals
melting points and boiling points increase with increasing atomic number
high electron affinities
change state as move down the family, with fluorine and chlorine existing as gases at room temperature while bromine in a liquid and iodine is a solid
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Noble Gas Element Family
The highlighted elements of this periodic table belong to the noble gas element family.
Todd Helmenstine
The noble gases are a family of nonreactive nonmetals. Examples include helium and argon.
Group 18 or VIIIA
Noble Gases or Inert Gases
8 valence electrons
typically exist as monatomic gases, although these elements do (rarely) form compounds
stable electron octet makes these elements nonreactive (inert) under ordinary circumstances
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Sources
Fluck, E. (1988). "New Notations in the Periodic Table" (PDF). Pure Appl. Chem. IUPAC. 60 (3): 431–436. doi:10.1351/pac198860030431
Leigh, G. J. (1990). Nomenclature of Inorganic Chemistry: Recommendations. Blackwell Science. ISBN 0-632-02494-1.
Scerri, E. R. (2007). The periodic table, its story and its significance. Oxford University Press. ISBN 978-0-19-530573-9.
