Group 1: Hydrogen and Alkali Metals

Group 1 elements also called alkali metals. Among the eighteen groups of the Periodic table, Group 1 consists of Hydrogen (H), Lithium ( Li), Sodium (Na), Potassium (K), Rubidium ( Rb), Cesium (Cs), Francium (Fr). They’re quite sensitive and simple to sever. Moreover, they carry both heat and electricity well. For the greatest part, alkali metals constitute solids at normal temperatures. However, some of them are highly reactive and can be formed into ionic compounds (Richens, 1997).

 

1. Electronic configuration

The electronic configuration of an atom describes the arrangement of the electrons in the subshells. It is used to understand the chemical properties and behaviors of the elements. Generally, Group 1 elements have one electron in the outermost orbital. The new power setup for Group 1 components is 1s2 2s2 2p6 ns1. The electronic configurations of group 1 elements are as follows:
H    [1] 1s1
Li   [3] 1s2 2s1 or [He] 2s¹
Na [11] 1s2 2s2 2p6 3s1 or [Ne] 3s¹
K   [19] 1s2 2s2 2p6 3s2 3p6 4s1 or [Ar] 4s1
Rb [38] 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s1 or [Kr] 5s1
Cs [55] 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s1 or [Xe] 6s1
Fr [87] 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 4f14 6s2 5d10 6p6 7s1 or [Rn] 7s1

 

2. Trend in the physical properties

Group 1 contains the most significant physical properties such as the ionic radii, the ionization energy and the density. These properties play a critical role in determining the chemical, physical and electrical properties of the elements in this group (Christy, 2015).

 

2.1. Atomic and ionic radii

During the study of the elements in the Group 1, the atom and ionic radii vary. This phenomenon is known as periodicity. The atomic and ionic radii of Group I elements can be explained by variation in the effective nuclear charge. The increase in the effective nuclear charge results in a shrinking of the atom size. In group from top to bottom atomic number increases due to which number of shell increases .So atomic radius as well as ionic radii increases . In group 1, atomic radius of lithium is smaller than francium. Atomic and ionic radius of group 1 elements is as under:

 

Atomic radius Group 1 periodic table of elements

 

Figure 1: Atomic radius of Group 1 elements

 

Ionic radius Group 1 periodic table of elements

 

Figure 2: Ionic radius of Group 1 elements

 

2.2. Ionization energy and density

The ionization energy and density of Group 1 of the Periodic Table is relatively low. Always take note that the maximum energy level of these elements contains just one electron. When moving down the periodic table, ionization energy and density also decrease. This is because the valence electron shell gets farther away from the nucleus, increasing the distance between the ion and the nucleus. However, it also takes more energy to remove the electron from a highly charged ion. This increases the distance required to overcome the electrostatic force (Christy, 2015).

 

First Ionization Energy Group 1 periodic table

 

Figure 3: First Ionization Energy of the Group 1 elements

 

2.3. Electropositive metallic character

The left side of the periodical chart is often associated with elements that have a strong electropositive property. This is because their ionization energy is low and they have a tendency to lose electrons. Also, metals are well-known for their strong electropositive nature. These elements are usually composed of a single valence electron. Electropositive elements tend to have positively charged cations. Alkali metals are also known to have a high electropositive character. This character increases down the group, so lithium has less while francium has highest metallic character among group 1 elements (Richens, 1997).

 

2.4. Melting and boiling point

The melting and boiling point of a chemical element is related to the size and number of atoms present in an element. A larger atomic radius decreases the melting and boiling point. In addition, a greater atomic mass decreases the melting and boiling point. As one goes through the spectrum of alkalis, the temperatures at which they melt and boil fall. This is due to the fact that the size of the atoms increases, reducing the attraction between the atoms. Lithium has highest melting point 179 °C and boiling point (1342°C) while cesium has lowest melting point 28.5 °C and boiling point (670.8°C) (Torrens & Castellano, 2020).

Melting and boiling point Group 1 periodic table of elements

Figure 4: Melting and Boiling Points of the Group 1 elements

 

2.5. Flame coloration

Generally speaking, flame coloration is the result of electron transitions in the flame. The atoms of metals are heated, and when electrons in the outer shell of an atom jump to a higher energy level, they emit visible light. Regrettably, the increased vitality is just temporary. As the electron relaxes back into its initial condition, it gives out a photon of beam with a certain energy. Several alkali metals give characteristic flame colors on fire (Richens, 1997).

Flame color Group 1 periodic table of elements

Table: Flame color of  Group 1 elements

3. Chemical properties

Elements in Group 1 of the Periodic Table are very reactive. They can form a stable ion. They are soluble in water and react with oxygen and hydrogen to form metal oxides and metal hydroxides.

 

3.1. Hydride

Hydride refers to a compound that consists of hydrogen and another element. In a hydride, the hydrogen atom is covalently bonded to an atom. Hydrides can take different forms, depending on the bonding between hydrogen and the hydride ions.Group 1 elements reacts with hydrogen and form hydrides of corresponding elements (Torrens & Castellano, 2020).

Group 1 elements reacts with hydrogen

Scheme 1: Group 1 elements reacts with hydrogen

3.2. Oxide and Hydroxide

Throughout the Periodic Table, oxide and hydroxide compounds are formed. Oxides are chemically basic, while hydroxides are acidic. Alkali metals reacts with oxygen and form oxides peroxides and superoxides (Richens, 1997).

Group 1 elements react with water and form hydroxides

Scheme 2: Oxides peroxide and superoxide from alkali metals

 

Group 1 elements react with water and form hydroxides

Scheme 3: Hydroxide from alkali metals

3.3. Carbonate and bicarbonate

Alkali metals forms carbonate and bicarbonate such as Lithium Carbonate (Li2CO3) Sodium Carbonate (Na2CO3) Potassium Carbonate (K2CO3) Rubidium Carbonate (Rb2CO3) Cesium Carbonate (Cs2CO3) while bicarbonate are LiHCO3, NaHCO3, KHCO3, RbHCO3, CsHCO3. Sodium and potassium carbonates are among the most common alkali metals. They are also among the most reactive elements on Earth. They react rapidly and vigorously with water to form alkalies. Carbonates decompose into carbon dioxide and oxide ions when heated (Torrens & Castellano, 2020).

 

4.Anomalous behavior of lithium

Among the alkali metals, lithium has a number of anomalous properties. These properties are not present in the other alkali metals. They are characterized by high electronegativity, high polarizing power, low standard potential, and small size. Lithium has a small size compared to other alkali metals. It is also one of the lightest solid elements. It is also a hard metal and has a high melting and boiling point (Richens, 1997).

 

4.1. Lithium compounds

Lithium compounds are relatively stable, but they decompose when they are exposed to heat. . Water solubility is lower for lithium compounds compared to those of alkali metals. Also, their solubility in organic solvents is only slightly above average. Lithium is also less reactive than other alkali metals. It is not able to form solid hydrogen carbonates. It produces lithium oxides as well as nitride when exposed to nitrogen. Lithium hydride has high ionization enthalpy and is less electropositive than other group 1 hydrides. Lithium hydride also has no vacant d-orbital in the valance cell (Torrens & Castellano, 2020).

 

4.2. Lithium ions

Lithium ions have a high positive charge density, a high polarising power, and a high nuclear charge. These properties are similar to those of magnesium ions. Lithium is also the strongest reducing agent. It reacts with nitrogen, carbon, and oxygen to form nitride, monoxide, and oxides. Lithium is also the hardest alkali metal. It is also the only alkali metal that can form monoxide. It also has the lowest standard potential of all alkali metals (Christy, 2015).

 

5. Uses of group 1 elements

Important uses of group 1 elements include glass, air purification on spaceships, lubricants, a wide range of industries, from pharmaceuticals and chemicals to food and drink. They are also used in research. The most accurate clocks are made of cesium. Some cesium alloys explode when they come in contact with water. Other uses include the production of nitric acid, vegetable oils, and margarine. Some are used as catalysts in industrial processes. They also produce sulphuric acid and ammonia. Lithium is used in batteries, electronics, and in air treatment. It is also used in aluminum production (Torrens & Castellano, 2020).

 

Conclusion

A contemporary periodical table allows us to list the elements in sequence of escalating atomic number. The periodic table has changed over the last 150 years to reflect the changes in scientific knowledge. The periodic table is useful for modern scientists because it provides a guide for predicting chemical reactions. Its symbol is also useful for students.

 

References

1. Richens, D. T. (1997). The chemistry of aqua ions: synthesis, structure, and reactivity: a tour through the periodic table of the elements. New York: Wiley.
2. Torrens, F., & Castellano, G. (2020). Periodic table. In New Frontiers in Nanochemistry (pp. 403-425). Apple Academic Press.
3. Christy, A. G. (2015). Causes of anomalous mineralogical diversity in the Periodic Table. Mineralogical Magazine, 79(1), 33-49.