Development of the periodic table

DEVELOPMENT OF THE PERIODIC TABLE

ORIGIN OF THE CHEMICAL NAMES AND SYMBOLS• Alchemy refers to both

an early form of the investigation of nature and an early philosophical and spiritual disciplines. Alchemists were known in different aspects and one of these is their popular culture, the process of changing some elements into gold.

• They were the first to introduce the symbols of the elements in the Middle Ages. This practice of using symbols has influenced modern chemists and helped them to work easily with the elements.

• Modern chemists use symbols for each element to facilitate writing and for convenience. They assigned each element unique symbols. This system of chemical symbols was invented by Jons Jacob Berzelius.

• Each element’s symbol has a different origin. Some of the element’s symbol are either the initial letter of the element or a combination of the first or another letter from the Latin or English name of the elements.

SOME ELEMENTS WITH SYMBOLS DERIVED FROM

ITS INITIAL LETTER

SOME ELEMENTS WITH SYMBOLS DERIVED FROM THE COMBINATION OF ITS

FIRST AND ANOTHER LETTERSYMBOL NAME SYMBOL NAME

B BORON Br BROMINEI IODINE Ir IRIDIUMC CARBON Cl CHLORINEH HYDROGEN He HELIUMN NITROGEN Cr CHROMIUMO OXYGEN Zn ZINCK POTASSIUM (LATIN;

KALIUM)Fe IRON (LATIN;

FERRUM)

• Aside from Latin and English names, some elements’ names and symbols were derived from the scientists’ or discoverers’ names such as Bohrium (Bh) named after Neils Bohr and Curium (Cu) for Marie Curie . Countries or places where it was discovered (example, Californium derived from California, mythology (example, Palladium derived from Pallas Athena), planets (Plutonium from the planet Pluto, its Greek (like Xenon, from the Greek word xenos; “foreign”) or German names (like Zinc from German zinken, “point”), colors (example Indium from the Greek word indium, “indigo”). majority of the elements in the periodic table have symbols consisting of two letters with the first letter capitalized. As chemists discovered more elements, they began to observe the arrangement of each element through patterns in their properties. These patterns helped the chemists decipher the elements better.

ORIGIN OF THE PERIODIC TABLE

• Chemists were not satisfied with the use of symbols for each element. They tried to arrange the elements. The arrangement of elements on patterns paved the way to the tabulation of the elements according to its chemical and physical properties suitably called the periodic table of elements.

ANTOINE LAVOISIER’S FIRST CLASSIFICATION

• In 1789, Antoine Lavoisier, a French physicist-chemist published a book that contained the classification of elements based on their similar properties. He arranged the elements into groups. Unfortunately, his work did not progress until his death in 1794.

DÖBEREINER’S TRIAD

• In 1817, Johannes Wolfgang Döbereiner, a German chemist, studied three elements and noticed similarities among the properties of metals such as Ca, Ba and Sr. He continued to study another group of three elements, Cl, Br and I. Döbereiner predicted that there is closeness among the atomic masses (traditionally called atomic weight) of the said elements.

• He concluded that the atomic mass and the density of the middle element in each triad is the approximate average if the masses and densities of the first and the third elements. Attempts were made to arrange the elements into triads in 1850. Nevertheless, more reliable measurements were introduced and speculations on the atomic mass of the middle element became less accurate.

DE CHANCOURTOIS’S TELLURIC HELIX

• In 1863, A.E. Beguyer de Chancourtois had the idea to plot the elements in a spiral around the surface of the cylinder divided into 16 vertical sections according to the elements’ atomic masses. In every vertical strip, the elements with the same physical and chemical properties were grouped together. He called his device telluric helix.

• He stated from the results of his experiments that the properties of elements were the same as the properties of numbers. His idea seemed tenable enough at first but failed to muster support.

NEWLANDS’ OCTAVES

• Although Döbereiner’s triads proved to be significant and de Chancortois idea did not gain support at that time these were used as bases for seeking further classification of elements. In 1869, John Newlands, an English chemist presented another way of classifying elements.

• He arranged all the elements known at that time in order of their atomic masses beginning with lithium and noted that the eighth element has similar properties to the first element, the ninth to the second, and the tenth to the third and so on. He compared their relationship to the octaves of musical notes. He then called this pattern the Law of Octaves.

MEDELEEV’S PERIODIC TABLE AND MEYER’S PERIODIC PROPERTY GRAPH

• In 1869, Russian chemist Dmitri Ivanovich Medeleev and German chemist Julius Lothar Meyer, working independently presented closely identical version of arranging the elements based on their increasing properties. Both scientists proposed the periodic law which states that the properties of elements are periodic functions of their atomic masses.

Dmitri Mendeleev Lothar Meyer

WILLIAM RAMSAY’S WORK ON NOBLE GASES

• Between 1893 and 1898, Sir William Ramsay, John Strutt or Lord Rayleigh and Morris Travers made a research not related to the periodic table and worked together to find out if there are unidentified elements existing in the atmosphere.

Sir William Ramsay Morris Travers

• In 1894, Ramsay and Rayleigh isolated argon from atmospheric nitrogen. Argon, the first noble gas, came from the Greek work argos meaning “the lazy one” . In 1895, Ramsay discovered the inert gas helium (derived from Greek word helios, meaning sun). Later on, Ramsay and Travers discovered more gases such as krypton (hidden), neon (new) and xenon (stranger). Mendeleev added a new group to his periodic table, the Group O or Group VIII for the group of unreactive gases now called the noble gasses.

MOSELEY’S WORKS ON ATOMIC NUMBERS

• In 1913, English physicist Henry Moseley suggested that atomic mass is not the property that governs periodicity, a discovery he got from his experiments on the X-ray emission spectra. He observed that the frequencies of X-ray emitted from atoms of elements were correlated with the sizes of their nuclear charges. He assigned a whole number to the size of the nuclear charge of the atom and called this atomic number.

• It was later proved that the atomic number was the nuclear charge discovered by Ernest Rutherford. He discovered that the atomic number differs from the preceding element in the table. His work becomes a significant discovery to the development of the periodic table because he was able to solve the irregularities in the Mendeleev’s periodic table.

• Moseley concluded that is its better to explain the trends in Mendeleev’s table if the elements were arranged according to increasing atomic number. The periodic law was restated as “the properties of the elements are periodic functions of their atomic numbers.”

THE MODERN PERIODIC TABLE

• By looking at the periodic table, we can see that the elements are arranged horizontally in the order of increasing atomic numbers. Each element is identified by its symbols placed at the middle of the square; the atomic number and the atomic mass are also included.

THE GROUPS

• The vertical columns are called groups or families. The elements in each column have similar chemical properties due to their similarities in the number of electrons in their outer shells or in their highest principal energy level. The periodic table has 18 vertical columns. The elements in a group are also identified into two categories such as Family A or the representative elements and the Family B or the transition metals.

GROUP A OR FAMILY A (REPRESENTATIVE ELEMENTS)

• Group IA – Alkali Metal• Group II A – Alkaline Earth Metals• Group IIIA – Aluminum Group/ Boron Family• Group IVA – Carbon Family• Group VA – Nitrogen Family• Group VIA – Oxygen Family or Chalcogens• Group VIIA – Halogens• Group VIIIA – Group 0 or Noble/ Inert Gases

GROUP B OR FAMILY B (TRANSITION ELEMENTS)

• Transition elements are found in between Group IIA and Group IIIA and are referred to as the d-block while the inner transition elements (lanthanides and actinides) are found at the bottom of the table and are refered as the f-block.

THE PERIODS

• Notice that the periodic table consists of several horizontal rows called the periods or series. There are seven periods which are designated as 1,2,3,4,5,6 and 7. the elements belonging to the same periods have different properties.

• Period 1 has two elements (hydrogen and helium) corresponding to the number of electrons in the s-sublevel having their electrons occupying only one main energy level.

• Periods 2 and 3 each has eight elements corresponding to the eight electrons in the s and p block.

• Periods 4 and 5 each has eighteen elements corresponding to the electrons in the s, p and d sublevels

• The last two periods are called the inner transition elements. The lanthanide series is then called the rare-earth elements and the actinide series, the heavy rare earth elements.

• Period 6 has 32 elements corresponding to the 32 electrons in the s, p, d, and f sublevels. To make this period fit the 18-member maximum arrangement of elements, the 14 elements from atomic numbers 58 to 71 are removed and placed at the bottom of the table to form the lanthanide series.

• Period 7 also includes 14 elements (from atomic number 90 through 103) which were placed at the bottom part of the table to form the actinide series.

QUIZ: Identify the scientist who contributed the following ideas in the development of the periodic table. Choose your answers from the choices given on the right.• Antoine Lavoisier• Johannes Döbereiner• A.E. Beguyer de Chancourtois• John Newlands• Dmitri Mendeleev• Lothar Meyer• Sir William Ramsay• Henry Moseley

• Antoine Lavoisier• Johannes Döbereiner• A.E. Beguyer de

Chancourtois• John Newlands• Dmitri Mendeleev• Lothar Meyer• Sir William Ramsay• Henry Moseley

1. He made a device called a telluric helix which group elements according to their similar chemical and physical properties.



2. A French physicist-chemist who published a book that contained the classification of elements based on their similar properties.



3. He researched on identifying elements existing in air which are added in the periodic table grouped as noble gases.



4. He grouped elements in traids.



5. He formulated the law of octaves.



5. He arranged elements according to increasing atomic weights.



6. He arranged elements according to increasing atomic number.

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Development of the periodic table