Families of elements in the periodic table

Families of Elements 

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The periodic table consists of 118 elements, with the first being Hydrogen (atomic number 1) and the last being Oganesson (atomic number 118). In accordance with the periodic law, all elements on the periodic table are arranged in order of increasing atomic number, that is; the number of protons in an atom's nucleus. 

Elements in the periodic table are put into families which will include the following;

• Groups

• Periods

• Transition Metals 

• Lanthanide Series

• Actinide Series

 

Elements in the same group may be said to belong to a family since they show similar properties because their atoms have the same number of valence electrons. At the same time, certain properties of elements in the same group show a gradual change with an increase in atomic number. Such gradual change of property within a group is termed as group trend.

Please read more on the periodic table and classification of elements here.

Recall that the old periodic table of elements comprise of 8 groups numbered (I - VIII).

Note: The modern periodic table comprises of 18 groups.

As stipulated above, certain elements make up members or families in the periodic table since these elements show similar properties or trend which changes with an increasing atomic number.

The families of elements within the periodic table are explained below:

You can read the introduction to chemistry, careers in chemistry and the scientific approach here.

 

Group I Elements

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The group I elements are termed the alkali metals. This is so because they react with water to form alkaline (or basic) solutions, and strong bases called alkalies.

The group I elements include Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Caesium (Cs), and Francium (Fr). They are univalent elements since they have only one electron in their outermost shell (termed valence electron).

The group one elements (alkali metals) show the following properties:

• They are good reducing agents since they can readily donate their one electron to form a univalent cation.

• They are soft silvery-colored shiny metals that can be easily cut with a knife.

• They are good conductors of electricity and heat.

• They react vigorously with cold water to form an alkaline solution, liberating hydrogen gas in the process. For this reason, they are termed alkali metals. An equation is shown below:

• 2Na_(s) + 2H₂O_(l) -> 2NaOH_(aq) + H_2(g)

  2K_(s) + 2H₂O_(l) -> 2KOH_(aq) + H_2(g)

• The oxides of group I elements dissolve in water to give a very strong alkaline solution. This is shown via the equation below:

• K₂O_(s) +H₂O_(l) -> 2KOH_(aq)

  Na₂O_(a) +H₂O_(l) -> 2KOH_(aq)

Please read on rate of chemical reaction here.

 

Group II Elements 

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The group II elements are termed alkaline earth metals. This is so because their oxides and hydroxides are alkaline (basic); and they are found as oxides and hydroxides inside the earth.

Group II elements include Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), Barium (Ba), and Radium (Ra). They are divalent elements since they ionize by giving out their 2 valence electrons.

The alkaline earth metals show the following 
properties:

• They ionize by donating their two valence electrons; hence making them good reducing agents.

• They are soft silvery-colored metals, ductile, malleable, and can conduct both heat and electricity.

• Beryllium does not react with cold water or steam, magnesium reacts with steam only while calcium reacts slowly with cold water to liberate hydrogen gas. In this regard, their reactivity increases down the group.

• The oxides of beryllium and magnesium are insoluble in water while that of others dissolve in water to form an alkali. This is shown in the equation below:

• CaO_(s) +2H₂O_(l) -> Ca(OH)_2(aq

Please read on the chemical properties of matter here.

 

Group III

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In the modern IUPAC notation, the traditional group III elements are currently called Group 3A, IIIA, XIII or Group 13 elements. Group 13 elements belong to the boron family.

The group 13 elements include: Boron (B), Aluminum (Al), Gallium (Ga), Indium (In) and Thallium (Tl). They are trivalent elements with an oxidation number of +3.

Below are properties of group IIIA elements:

• They are reducing agents in nature since they can donate their three valence electrons to form electrovalent compounds.

• Only aluminum can react with steam at about 750^oC to liberate hydrogen gas.

• The oxide and hydroxide of aluminum are amphoteric in nature. This implies that they have both acidic and basic properties. This is shown via the equation below:

Al₂O_3(s) + 3H₂SO_4(aq) -> Al₂(SO₄)_2(aq) + 3H₂O_(l)

2Al(OH)_3(s) + NaOH_(aq) -> NaAl(OH)_4(aq)

You can read on physical and chemical change in chemistry here.

 

Group IV

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In the modern IUPAC notation, the traditional group IV elements are currently called Group 4A, IVA, XIV or Group 14 elements.

The group 14 elements are called the carbon group or tetrels. The name "tetrels" emanate from the Latin word "quattuor" meaning four, referring to the four valence electrons these elements have, which are in the outermost shell. The elements in this group include Carbon (C), Silicon(Si), Germanium (Ge), tin(Sn) and lead (Pb) and flerovium (Fl)..

Group 14 elements of the periodic table often form covalent compounds, showing distinct properties. These are listed below:

• They exhibit two oxidation states: that is; +2 and +4 respectively. Due to inert pair effect of electrons in the s-orbital of the valence shell, the +2 oxidation state becomes more prominent down the group.

• Electropositivity increases down the group. Carbon is a non-metal, silicon and germanium are metalloids while tin and lead are metals.

• Carbon does not react with water in any form; but silicon and tin react with steam at red heat to form +4 state oxides while liberating hydrogen gas. It is shown in the equation below:

• Si_(s) + 2H₂O_(l) -> SiO_2(s) + 2H_2(g)

Note: Carbon is fundamental to life, forming the basis of organic compounds. In addition, its unique ability to catenate allows for complex structures like diamonds, graphite and various organic compounds.

You can read a brief introduction to hydrocarbons here.

 

Group V

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In the modern IUPAC notation, the traditional group V elements are currently called Group 5A, VA, XV or Group 15 elements.

The group 15 elements comprise of Nitrogen (N), Phosphorus (P), Arsenic (As), Antimony (Sb), Bismuth (Bi) and Moscovium (Mc) respectively. They are also termed as the pnictogens or "nitrogen group".

Note: The name pnictogens come from the Greek word "pnigo", meaning "to choke" or "to suffocate". This is a reference to the fact that nitrogen can be suffocating in high concentrations because of its ability to displace oxygen. Meanwhile, understand that nitrogen in itself is not considered toxic.

Group 15 elements are characterized by their outer electronic configuration of ns² np³. Also, they show a progression (down the group) from non-metals to metalloids and finally to metals.

Below are properties of group 15 elements:

• They exhibit oxidation states of -3, +3 and +5. 

• They show non metallic, metaloid and metallic trend down the group. For instance, nitrogen and phosphorus are non-metals, arsenic and antimony are metalloids while bismuth and moscovium are metals.

• They are electron acceptors, making them oxidizing agents in nature.

• They form oxides that dissolve in water to form acids (with the exception of nitrogen(I)oxide).

You can read on acids here.

 

Group VI

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In the modern IUPAC notation, the traditional group VI elements are currently called Group 6A, VIA, XVI or Group 16 elements. These elements are known as the chalcogens or oxygen family.

Elements in group 16 include Oxygen (O), Sulphur (S), Selenium (Se), Tellurium (Te), Polonium (Po) and Livermorium (Lv). They share a general outer electron configuration of ns² np⁴, meaning they have six valence electrons. In this regard, they will typically gain two electrons to achieve a full octet configuration. 

They show the following properties:

• Oxygen is the most abundant group 16 element present in the atmosphere and earth's crust. It is crucial for cellular respiration, and consequently, life.

• They are non-metals and exist as solid at room temperature. However, only oxygen exists as a gas at room temperature.

• They are electron acceptors, thus making them good oxidizing agents.

• They do not react with water in any form. However, oxygen and sulphur combine directly with hydrogen to yield water and hydrogen sulphide respectively. This is shown via the equation below:

• 2H_2(g) + O_2(g) -> 2H₂O_(l)

• H_2(g) + S_(s) -> H₂S_(g)

You can read on the kinetic theory of gases here.

 

Group VII

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In the modern IUPAC notation, the traditional group VII elements are currently called Group 7A, VIIA, XVII or Group 17 elements.

The group 17 elements are termed halogens, meaning salt formers. They are highly reactive nonmetals with seven valence electrons, making them a powerful lone electron acceptor, in order to achieve a stable octet configuration. They include Fluorine (F), Chlorine (Cl), Bromine (Br), Iodine (I) and Astatine (At).

Please read on salts in chemistry here.

The halogens show the following properties:

• They ionize to form univalent anions.

• They exist as diatomic molecules.

• Since they accept one electron, all halogens are good oxidizing agents.

• They exhibit group trend. In this regard, fluorine and chlorine are gases, bromine is a liquid while iodine and astatine are solids at room temperature.

• They react with metals to form salts. An example is shown in the equation below:

• 2Na_(s) + Cl_2(g) -> 2NaCl_(s)

 

Group VIII or 0

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In the modern IUPAC notation, the traditional group VIII elements are currently called Group 8A, VIIIA, XVIII or Group 18 elements.

The elements making up group VIII are termed as rare gases, noble gases, or inert gases. This is so because they are non-reactive, making them exist freely as monoatomic molecules in the atmosphere.

The elements comprising this group include Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe) and Radon (Rn).

Group VIII elements are in the far-right column of the periodic table and are known for being chemically inert since they have a full outer electron shell (octet configuration), making them very stable and non-reactive. 

The noble gases show the following properties:

• They are chemically inert (unreactive) because of their complete octet or duplet configuration.

• They exist as colorless, odorless, and tasteless gases at room temperature

• They have low boiling and melting points. 

• Helium is used for balloons and in deep-sea diving mixtures. Neon and Argon are used for lighting and signs. Krypton is used in specialty lighting while Xenon is utilized in camera flashes and car headlights. 

Please read on the uses of chemistry here.

 

The image below shows the arrangement and families of elements on the periodic table. Please take note to observe the position of these families of elements on the table.

 

Transition Metals

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These are elements found between group II and XIII of the periodic table. In the modern IUPAC notation, the transition metals or elements occupy groups III (3) through XII (12) respectively. They are grouped into four transition series.

The first transition series consists of the following elements:

Scandium (Sc), Titanium (Ti), Vanadium (V), Chromium (Cr), Manganese (Mn), Iron (Fe), Cobalt (Co), Nickel (Ni) , Copper (Cu) and Zinc (Zn).

The second transition series are listed below:

Yttrium (Y), Zirconium (Zr), Niobium (Nb), Molybdenum (Mo), Technetium (Tc), Ruthenium (Ru), Rhodium (Rh), Palladium (Pd), Silver (Ag), and Cadmium (Cd)

The third transition series elements are listed below:

Lanthanum (La), Hafnium (Hf), Tantalum (Ta), Tungsten (W), Rhenium (Re), Osmium (Os), Iridium (Ir), Platinum (Pt), Gold (Au) and Mercury (Hg)

The fourth series of transition metals include:

Actinium (Ac), Rutherfordium (Rf), Hafnium (Hf), Seaborgium (Sg), Bohrium (Bh), Hassium (Hs), Meitnerium (Mt), Darmstadtium (Ds), Roentgenium (Rg) and Copernicium (Cn).

The transition elements show the following properties:

• High tensile strength.

• High melting and boiling points.

• Variable oxidation states.

• Formation of colored ions. 

• Formation of complex ions.

• Paramagnetic in mixture.

• They have catalytic ability.

You can read on dynamic equilibrium in chemistry here.

 

Lanthanides (Rare Earth Elements)

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The lanthanides are found in period six of the periodic table. They are a group of 15 metallic chemical elements with atomic numbers 57 through 71, ranging from lanthanum (La) to lutetium (Lu). They are also known as the rare earth elements, not because they are truly scarce, but rather because they were historically found in concentrated ores from only few locations, making them difficult to extract and refine. Simply put, lanthanides are actually quite abundant, but the difficulty of isolating, extracting and purifying them from their ores is the primary reason for it being considered as rare earth elements. 

Please read on ionic theory and electrolysis here.

Lanthanides are located in the first row at the bottom of the periodic table. These elements are notable for their similar chemical and physical properties, and their atoms fill the 4f orbitals. 

Below are elements making up the lanthanide series:

Lanthanum (La), Cerium (Ce), Praseodymium (Pr), Neodymium (Nd), Promethium (Pm), Samarium (Sm), Europium (Eu), Gadolinium (Gd), Terbium (Tb), Dysprosium (Dy), Holmium (Ho), Erbium (Er), Thulium (Tm), Ytterbium (Yb), and Lutetium (Lu). 

 

Lanthanides exhibit the following properties:

• Lanthanides are soft, silvery-white metals that tarnish in air.

• They have high melting and boiling points.

• They are good conductors of heat and electricity.

• They are reactive with water, acids, and most nonmetals.

• They are strongly paramagnetic.

• They show a steady decrease in atomic and ionic radii across the series. This makes them quite difficult to separate.  

 

Actinides (and the Artificial Elements)

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The actinides are are present in the seventh period of the periodic table. They are a series of 15 radioactive metallic elements with atomic numbers 89 through 103. These include naturally occurring elements like uranium and thorium, as well as many others that are artificially created.

Please read more on nuclear chemistry and radioactivity here.

Below are elements comprising the actinide series.

Actinium (Ac), Thorium (Th), Protactinium (Pa), Uranium (U), Neptunium (Np), Plutonium (Pu), Americium (Am), Curium (Cm), Berkelium (Bk), Californium (Cf), Einsteinium (Es), Fermium (Fm), Mendelevium (Md), Nobelium (No), and Lawrencium (Lr).

The elements with atomic number 93 through 103 are known as the artificial elements.This is so because they do not occur naturally, but were formed during nuclear reactions.

• The artificial elements are: Americium (Am), Curium (Cm), Berkelium (Bk), Californium (Cf), Einsteinium (Es), Fermium (Fm), Mendelevium (Md), Nobelium (No), and Lawrencium (Lr). 

 

Actinides show the following properties:

• They are highly radioactivity. In fact, all actinides are radioactive and undergo decay, making them crucial in nuclear power generation and weapons.

• They are heavy metals that can ignite easily in air. For this reason, they are said to be pyrophoric.

• They have high melting and boiling points. 

• The actinides have also got a high density and strong metallic bonds.