The German chemist Johann Dobereiner attempted one of the earliest attempts to classify the elements according to their chemical and physical properties. Dobereiner discovered the rule of threes for chemically related elements in 1817.
Calcium, strontium, and barium; lithium, sodium, and potassium; chlorine, bromine, and iodine are just a few examples. One element in each set of three had an atomic weight exactly in the middle of the other two elements. The pattern was too striking to be a mere fluke. Dobereiner put out the Law of Triads in 1829 based on his research.
Subsequently, his discoveries sparked the efforts of other scientists to identify patterns among much larger collections of materials.
The French geologist Alexandre-Emile Beguyer de Chancourtois tried again in 1862 to classify the elements based on their qualities.
He came up with a spiral graph style arrangement of the elements on a cylinder, with the elements lined up vertically by similarity.
Why Is The Periodic Table Arranged How It Is?
The periodic table’s format was designed to provide a clear illustration of the chemical elements. The position of each of these elements in the periodic table has been carefully calculated.
Since its beginnings, the periodic table’s arrangement has evolved. That’s because humans have found and synthesised new elements, expanding the periodic table. Let’s take a trip down memory lane before we delve into the details of the periodic table.
Dmitri Mendeleev – Father of the Periodic Table
According to the Royal Society of Chemistry, Russian chemist and inventor Dmitri Mendeleev deserves credit as the “founder” of the periodic table. Mendeleev, a Russian chemist, taught at St. Petersburg University in the 1860s and was well-liked by his students.
No comprehensive, up-to-date organic textbooks suitable as required reading existed at the time. In light of this need, Mendeleev set out to compose one, with the twin goals of standardising the classification of elements and answering the question of what constitutes an authoritative text on the subject.
At the time of Mendeleev, this wasn’t as easy as it sounds because there were a lot of roadblocks to get over. Less than half of the elements in use were known at that time, and some of the identified elements had inaccurate information.
To try and grasp what Mendeleev went through, we can use the example of a challenging jigsaw puzzle with half the pieces bent out of shape.
First Major Change of The Periodic Table
In the years between 1895 and 1901, scientists discovered an altogether new group of elements called the noble gases, prompting the first major revision to the periodic table.
The term “noble gases” was coined to describe a group of chemical elements that were thought to be unreactive, hence their inability to form compounds with other elements.
(Today, we know that they do, in fact, combine chemicals—but not willingly.) These were simply appended to the list under helium in a new column.
An English physicist who trained with Ernest Rutherford, Henry Gwyn-Jeffries Moseley, performed the first comprehensive update to the entire periodic table.
In 1914, Moseley proved that the number of positive charge units (later named -protons) associated with an atomic nucleus could be assigned a number.
Minor inconsistencies in Mendeleev’s system vanished after the periodic table was rearranged to correspond with atomic number rather than atomic weight.
The Birth of the Periodic Table
The periodic table, as we know it today, is the result of centuries of scientific inquiry and discovery. It all began with early chemists and alchemists who sought to understand the properties of different substances.
However, the breakthrough came in the 19th century when Dmitri Mendeleev, a Russian chemist, organized the known elements into a systematic chart.
Mendeleev’s stroke of genius was recognizing that elements could be grouped based on their properties and atomic weights. He arranged the elements into rows and columns, leaving gaps for undiscovered elements that he predicted would fill those spaces.
His prediction of these missing elements, based on their expected properties, turned out to be astonishingly accurate.
The Modern Periodic Table
Today’s periodic table is a refined and expanded version of Mendeleev’s original creation. It consists of 118 known elements, each with its unique properties and characteristics. Elements are arranged in order of increasing atomic number, which is the number of protons in an atom’s nucleus.
The periodic table is divided into rows, known as periods, and columns, known as groups or families. Elements within the same group share similar chemical properties because they have the same number of valence electrons, which are responsible for an element’s chemical behavior. Elements in the same period have the same number of electron shells.
Patterns and Trends
One of the most captivating aspects of the periodic table is the recurring patterns and trends it exhibits. Here are some key examples:
- Atomic Size: As you move from left to right across a period, atomic size generally decreases. This trend is due to an increase in the number of protons, which leads to a stronger positive charge in the nucleus, pulling the electrons closer.
- Electronegativity: Electronegativity, or an element’s ability to attract electrons in a chemical bond, tends to increase from left to right across a period. Elements on the right side of the table are more likely to gain electrons in chemical reactions.
- Metallicity: Elements on the left side of the periodic table (alkali metals and alkaline earth metals) are generally metals, while those on the right side (nonmetals and metalloids) are nonmetals. The transition metals in the middle exhibit properties of both metals and nonmetals.
- Valence Electrons: Elements in the same group have the same number of valence electrons. For example, all elements in Group 18 (noble gases) have eight valence electrons, making them stable and chemically unreactive.
One’s ability to deduce an element’s atomic number is the first and most important thing to learn from the periodic table. The atomic number of an element is equal to the sum of its protons. It also serves as a useful indicator of the element’s chemical properties.
The number of protons in various atoms can be described; for instance, carbon atoms have six, hydrogen atoms have one, and oxygen atoms have eight.