Element Families of the Periodic Table

Element Families

Because element properties are largely determined by the behavior of valence electrons, families and groups may be the same. However, there are different ways of categorizing elements into families. Many chemists and chemistry textbooks recognize five main families:

5 Element Families

1. Alkali metals
2. Alkaline earth metals
3. Transition metals
4. Halogens
5. Noble gases

9 Element Families

Another common method of categorization recognizes nine element families:

1. Alkali Metals: Group 1 (IA) - one valence electron
2. Alkaline Earth Metals: Group 2 (IIA) - two valence electrons
3. Transition Metals: Groups 3-12 - two valence electrons
4. Boron Group or Earth Metals: Group 13 (IIIA) - three valence electrons
5. Carbon Group or Tetrels: Group 14 (IVA) - four valence electrons
6. Nitrogen Group or Pnictogens: Group 15 (VA) - five valence electrons
7. Oxygen Group or Chalcogens: Group 16 (VIA) - six valence electrons
8. Halogens: Group 17 (VIIA) - seven valence electrons
9. Noble Gases: Group 18 (VIIIA) - eight 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:

1. The older IUPAC system used Roman numerals together with letters to distinguish between the left (A) and right (B) sides of the periodic table.
2. The CAS system used letters to differentiate the main group (A) and transition (B) elements.
3. 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 today.

Alkali Metals or Group 1 Family of Elements

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. Hydrogen is not considered an alkali metal because the gas does not exhibit the typical properties of the group. However, under the right temperature and pressure conditions, hydrogen can be an alkali metal.

• Group 1 or IA
• Alkali Metals
• One 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

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Secrets of Periodic Table Element Families

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Alkaline Earth Metals or Group 2 Family of Elements

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)
• Two valence electrons
• Metallic solids, harder than the alkali metals
• Shiny, lustrous, oxidize easily
• High thermal and electrical conductivity
• Denser 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 reacts only with steam
• Ionize to lose their valence electrons, so the ion has a +2 charge

Transition Metals Element Family

The largest family of elements consists 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-block and f-block metals have two valence electrons
• Hard metallic solids
• Shiny, lustrous
• High thermal and electrical conductivity
• Dense
• High melting points
• Large atoms exhibit a range of oxidation states

Boron Group or Earth Metal Family of Elements

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
• Three valence electrons
• Diverse properties, intermediate between those of metals and nonmetals
• Best-known member: aluminum

Carbon Group or Tetrels Family of Elements

The carbon group comprises elements called tetrels, which refers to their ability to carry a charge of four.

• Group 14 or IVA
• Carbon Group or Tetrels
• Four valence electrons
• Diverse properties, intermediate between those of metals and nonmetals
• Best-known member: carbon, which commonly forms four bonds

Nitrogen Group or Pnictogens Family of Elements

The pnictogens or nitrogen group is a significant element family.

• Group 15 or VA
• Nitrogen Group or Pnictogens
• Five valence electrons
• Diverse properties, intermediate between those of metals and nonmetals
• Best-known member: nitrogen

Oxygen Group or Chalcogens Family of Elements

The chalcogens family is also known as the oxygen group.

• Group 16 or VIA
• Oxygen Group or Chalcogens
• Six valence electrons
• Diverse properties, changing from nonmetallic to metallic as you move down the family
• Best-known member: oxygen

Halogen Family of Elements

The halogen family is a group of reactive nonmetals.

• Group 17 or VIIA
• Halogens
• Seven valence electrons
• Reactive nonmetals
• Melting points and boiling points increase with increasing atomic number
• High electron affinities
• State of the elements changes as you move down the family, with fluorine and chlorine existing as gases at room temperature, while bromine is a liquid, and iodine is a solid

Noble Gas Element Family

The noble gases are a family of nonreactive nonmetals. Examples include helium and argon.

• Group 18 or VIIIA
• Noble Gases or Inert Gases
• Eight valence electrons
• Typically exist as monatomic gases, although these elements do (rarely) form compounds
• Stable electron octet makes nonreactive (inert) under ordinary circumstances