ICH 101 Periodic Table. EBSU
HISTORY OF PERIODIC TABLE
The modern periodic table arranges the elements by their atomic numbers and periodic properties. Several scientists worked over almost a century to assemble the elements into this format.
Among the scientists who worked to created a table of the elements were, from left, Antoine Lavoisier, Johann Wolfang Döbereiner, John Newlands and Henry Moseley.
In 1789, French chemist Antoine Lavoisier tried grouping the elements as metals and nonmetals.
Forty years later, German physicist Johann Wolfang Döbereiner observed similarities in physical and chemical properties of certain elements. He arranged them in groups of three in increasing order of atomic weight and called them triads, observing that some properties of the middle element, such as atomic weight and density, approximated the average value of these properties in the other two in each triad.
A breakthrough came with the publication of a revised list of elements and their atomic masses at the first international conference of chemistry in Karlsruhe, Germany, in 1860. They concluded that hydrogen would be assigned the atomic weight of 1 and the atomic weight of other elements would be decided by comparison with hydrogen. For example, carbon, being12 times heavier than hydrogen, would have an atomic weight of 12.
British chemist John Newlands was the first to arrange the elements into a periodic table with increasing order of atomic masses. He found that every eight elements had similar properties and called this the law of octaves. He arranged the elements in eight groups but left no gaps for undiscovered elements.
In 1869, Russian chemist Dmitri Mendeleev created the framework that became the modern periodic table, leaving gaps for elements that were yet to be discovered. While arranging the elements according to their atomic weight, if he found that they did not fit into the group he would rearrange them. Mendeleev predicted the properties of some undiscovered elements and gave them names such as "eka-aluminium" for an element with properties similar to aluminium. Later eka-aluminium was discovered as gallium. Some discrepancies remained; the position of certain elements, such as iodine and tellurium, could not be explained.
German chemist Lothar Meyer produced a version of the periodic table similar to Mendeleev’s in 1870. He left gaps for undiscovered elements but never predicted their properties. The Royal Society of London awarded the Davy Medal in 1882 to both Mendeleev and Meyer. The later discovery of elements predicted by Mendeleev, including gallium (1875), scandium (1879) and germanium (1886), verified his predictions and his periodic table won universal recognition. In 1955 the 101st element was named mendelevium in his honor.
The 1869 periodic table by Mendeleev in Russian, with a title that translates "An experiment on a system of elements ... based on their atomic weights and chemical similarities." .
The concept of sub-atomic particles did not exist in the 19th century. In 1913, English physicist Henry Moseley used X-rays to measure the wavelengths of elements and correlated these measurements to their atomic numbers. He then rearranged the elements in the periodic table on the basis of atomic numbers. This helped explain disparities in earlier versions that had used atomic masses.
In the periodic table, the horizontal rows are called periods, with metals in the extreme left and nonmetals on the right. The vertical columns, called groups, consist of elements with similar chemical properties. The periodic table provides information about the atomic structure of the elements and the chemical similarities or dissimilarities between them. Scientists use the table to study chemicals and design experiments. It is used to develop chemicals used in the pharmaceutical and cosmetics industries and batteries used in technological devices.
GROUPS OF ELEMENTS IN PERIODIC TABLE
- Alkali metals.
- Alkaline earth metals.
- Rare earth metals.
- Crystallogens.
- Pnictogens.
- Chalcogens.
- Halogens.
- Noble gases
GROUP 1 ELEMENTS: they are also known as ALKALI METALS, examples are sodium, potacium, etc. They are highly electro positive and Tanish to exposure to air, they also react vigorously with water 💦,
GROUP 2 ELEMENTS: they are also known as ALKALINE EARTH METAL, examples include:
1. Magnesium
2. Calcium
GROUP 3 ELEMENTS: this group has no particular, examples
1. Boron
2. Aluminium
GROUP 4 ELEMENTS: Group 4 is the second group of transition metals in the periodic table. It contains the four elements titanium (Ti), zirconium (Zr), hafnium (Hf), and rutherfordium (Rf).
GROUP 5 ELEMENTS: Group 5 is a group of elements in the periodic table. Group 5 contains vanadium (V), niobium (Nb), tantalum (Ta) and dubnium (Db). This group lies in the d-block of the periodic table.
GROUP 6 ELEMENTS: Group 6, numbered by IUPAC style, is a group of elements in the periodic table. Its members are chromium (Cr), molybdenum (Mo), tungsten (W), and seaborgium
GROUP 7 ELEMENTS: Group 7, numbered by IUPAC nomenclature, is a group of elements in the periodic table. They are manganese (Mn), technetium (Tc), rhenium (Re), and bohrium .
GROUP 8 ELEMENTS: Group 8A (or VIIIA) of the periodic table are the noble gases, helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). The name comes from the fact that these elements are virtually unreactive towards other elements or compounds.
BLOCKS OF ELEMENTS IN PERIODIC TABLE
Periodic table blocks are sets of elements grouped by their valence electron orbitals. The four block names are s-block, p-block, d-block, and f-block. Should a new element be discovered, it will be in g-block. Each block indicates which electron sublevel is in the process of being filled.
Charles Janet introduced the concept of element blocks as an alternative to element groups (and also envisaged helix and left-step periodic tables).
Periodic Table Block Names
The block names come from the electron azimuthal quantum number values, which represent characteristics of spectroscopic lines: sharp (0), principal (1), diffuse (2), or fundamental (3). G-block gets its name because “g” is the next letter after “f”.
The four periodic table blocks are the basis for the main group (s- and p-blocks), transition metal (d-block), and inner transition metal (f-block) elements.
Properties of Periodic Table Blocks
S-Block
The s-block elements (except for helium) are on the left side of the periodic table.
With the exception of helium (and possibly hydrogen), all of the s-block elements are metals. The s-block includes the alkali metals and alkaline earth metals.
S-block elements tend to form soft solids with low melting points.
With the exception of helium, all s-block elements are electropositive and reactive.
P-Block
The p-block elements are on the right side of the periodic table. They include the last six element groups of the table (except for helium). P-block elements include all of the nonmetals (except hydrogen and helium), all of the metalloids, and the post-transition metals.
P-block elements can gain, lose, or share their valence electrons.
Most p-block elements form covalent compounds. The halogens form ionic compounds with s-block elements.
D-Block
D-block elements are the transition metals (groups 3-12).
D-block elements display properties between those of the highly reactive electropositive s-block elements and the more electronegative p-block elements. This is why they are called “transition” metals.
These elements are all metals, usually with two or more oxidation states.
D-block elements tend to have high melting points and boiling points.
Many of these elements form colored complexes and salts.
D-block elements tend to be good catalysts.
F-Block
The f-block elements or inner transition metals are the lanthanides and actinides. They are the two rows of elements found below the main body of the periodic table.
F-block elements display variable oxidation states.
Most f-block elements have high melting points.
These elements form colored complexes and salts, but they tend to be paler than those formed by d-block elements.
Many of the f-block elements (the actinides) are radioactive.
G-Block
The g-block elements will be elements beyond oganesson (element 118). As these elements have not yet been synthesized, their properties have yet to be determined.
Blocks vs Groups and Periods
Blocks, groups, and periods are three broad ways of classifying elements based on their position on the periodic table and common properties.
Blocks indicate which electron sublevel is being filled.
Groups are the vertical columns on the periodic table. Moving down a group adds a new electron subshell. For s-block elements, the group number is the number of valence electrons. for p-block elements, the group number is 10 plus the number of valence electrons. For d-block elements, the group numbers is (n-1) the number of electrons in the subshell plus the number of electrons in the valence shell.
Periods are the horizontal rows of the periodic table. The length of a period is determined by the number of electrons needed to fill the electron sublevel.
Assignment on this topic
THIS WAS THE ASSIGNMENT GIVEN TO 100 LEVEL STUDENTS AFTER THAT LECTURES
1 explain with suitable examples diagonal relationships in the periodic table
2a. What is electron affinity
2b. Show the variation in the periodic table
3. Defrentiate between the short and long form of periodic table
