What is the Periodic Table of Elements?
Created in 1869 by Russian scientist Dmitri Mendelev, the periodic table of elements works to organize all discovered chemical elements in 18 columns (each column represents a group of elements) and 7 rows (each row represents one period). Elements within the same group or column often act comparably to each other because they have the same number of electrons in their outermost shell. Elements in the same row or period share electrons in the same number of energy levels – as we move down the table, periods of elements are longer because it becomes increasingly difficult to fill outer shells with electrons.
The periodic table serves as a resource to quickly identify an element and its important identifying information – such as its atomic mass and chemical symbol. Additionally, the arrangement of the elements allows for recognizing different trends across the elemental properties. This grants scientists the ability to determine how characteristics like electronegativity and atomic radius are interrelated.
How are elements in the Periodic Table grouped together?
Elements within the Periodic Table can be organized into three central groups: metals, nonmetals, and metalloids. Nonmetals, as indicated by their name, can be differentiated from other elements at room temperature because they exist as gases or liquids. Typically, nonmetals serve as poor conductors of both electricity and heat – they are also not malleable or ductile. Apart from Hydrogen at the top left, nonmetals are congregated on the right portion of the table. Metalloids are physically similar to nonmetals but intermediaries in other properties of elements; some can be used as conductors of electricity and serve as vital semiconductors in technological devices like silicon, germanium, and arsenide. All other elements can be grouped under metals and make up the majority of elements within the periodic table.
What are Metals?
With the exception of Mercury, metals remain solid under normal conditions—this allows for them to be malleable and ductile and easily shaped into sheets or wires. Metals are also good conductors of electricity as they have free electrons that can easily move around and pass along energy; in particular, silver and copper are the two best conductors. Additionally, it requires very little energy to remove the outermost electrons in these elements which indicates that metals have low ionization energies. Since it requires little energy for metals to give up electrons, they often resist gaining an electron as this process requires more energy. As a result, metals are known to have low electron affinities.
Metallic bonding is an important characteristic of metals that allows for metals to form a bond with other elements to create a compound. Metals’ low ionization energies allow them to give up their loosely held electrons that become a binding force for the new compound and prevent other ions from disrupting the new bonds made. Interestingly enough, the metallic bond in these compounds is loosened but remains intact even when melted down—this bond can only be broken at melting point.
Different Groups of Metals
Based on differences in chemical properties, scientists have further divided metals into different groups within the periodic table: Alkali, Alkaline Earth, Transition (Lanthanides, and Actinides), and Basic Metals. Alkali metals (Group 1) are highly reactive and in nature, are found in compounds having reacted with air or water. They are also softer and more malleable than other metals with low melting points. Given their high reactivity, alkali metals can be traced back to ancient civilizations such as in China where they used to produce gunpowder. Alkaline Earth metals (Group 2) are less reactive than Group 1 metals but still fairly reactive. This group of metals derives its name from their oxide compounds called “alkaline earth” and also because they remain insoluble in water and solid in a fire. Elements in this group are known for their luster and silver color. Basic metals (in green on the table) generally display similar characteristics to metals as a whole – malleable, ductile, good conductors, and metallic luster. However, some metals in this group, like Tin, behave in nonmetallic ways and tend to have lower boiling and melting points.
Often seen as the bridge between the metals on the left and right sides of the periodic table, Transition metals (Group 3-12) are strong, lustrous, and good conductors of both heat and electricity. Given that there are nearly 100 transition metals, the chemical properties among these metals vary greatly. For example, Tungsten has a melting point of 3,400 degrees Celsius while Mercury is liquid at room temperature. Despite this variability, transition metals still have low ionization energies and are quick to lose electrons to form bonds with other elements. Transition metals also include two subgroups: Lanthanides and Actinides.
Lanthanides (Block 5d) are relatively soft metals that are silver-colored until exposed to air upon which they tarnish. They also are highly reactive with very high boiling and melting points. In earlier history, these elements were considered rare because it is difficult to distinguish between them. Actinides located at the bottom of the periodic table (atomic numbers 89 to 103) are considered special elements because of their unique properties. Due to their radioactivity and unstable isotopes, these elements are utilized in nuclear chemistry to release large amounts of energy. Compared to other metals, they are highly reactive and are silver-colored at room temperature.
In Summary
The Periodic Table serves to organize all known elements into an effective categorical tool making it easy to assess similarities and differences among elements. This is particularly useful given the expansive nature of metals and their subgroups within the table. Metals are greatly utilized in both scientific settings and our everyday lives because of their distinct chemical properties – high conductivity, low ionization energies, and low electronegativity.
Author: Aish Chitoor