Introduction to Periodic Table PDF

15‐01‐2025 Introduction to Periodic Table Historical background and Evolution of Modern Periodic Table Johann Dobereiner (Model of triads) In 1829, he classified some elements into groups of three, which he called triads. The elements in a triad had similar chemical prop...

15‐01‐2025 Introduction to Periodic Table Historical background and Evolution of Modern Periodic Table Johann Dobereiner (Model of triads) In 1829, he classified some elements into groups of three, which he called triads. The elements in a triad had similar chemical properties and orderly physical properties. Atomic mass of the central element was merely the arithmetic mean of the atomic masses of the other two elements and the properties of the middle element were in between those of the end members. 1780 - 1849 Drawback:  Concept was not applicable to all the known elements but only to a limited number of elements.  However, one point became clear that properties of the elements have some relationship with their Atomic masses/Atomic number. 1  15‐01‐2025 John Newlands (Law of Octaves)  According to this law, the elements when arranged in order of their increasing atomic masses.  He found that every eight elements had similar properties and called this the law of octaves.  Eighth succeeding element was the repetition of the first one like 8th note of the musical scale. 1838 - 1898  The system worked quite well for the lighter elements. For example, H, F and Cl show similar properties and similarly. Ex. Li, Na and K exhibit same characteristics.  The system, however, fails in the case of heavier elements as manganese has been placed along with nitrogen and phosphorus or iron has been placed along with oxygen and Sulphur, i.e., dissimilar elements have been grouped which is against the aim of classification. Lother Meyer's Curve  Emphasized physical characteristics of the elements.  Presented the classification in the form of curve.  Lother Meyer calculated the atomic volumes of the known elements by applying formula.  He plotted these atomic volumes against corresponding atomic masses.  A curve taking the form of sharp peaks and broad minima was obtained. 2  15‐01‐2025 The Curve  Alkali metals, having the largest atomic volumes, occupy the maxima of the curve.  The alkaline earth metals (Mg, Ca, Sr, Ba) occupy positions at about the mid-points on the descending portions of the curve.  The halogens (F, Cl, Br, I) occupy positions on the ascending portions of the curve.  The transition elements occupy minima of the curve.  On the basis of above observations Lother Meyer proposed: The physical properties of the elements are a periodic function of their atomic masses. Dmitri Mendeleev Proposed Periodic law: The properties of the elements are a periodic function of their atomic masses. A tabular arrangement of elements in rows and columns, highlighting the regular repetition of properties of elements is called a periodic table. Mendeleev arranged the elements between hydrogen and uranium, providing 90 spaces between these two elements, in order of increasing atomic masses. 3  15‐01‐2025  When Mendeleev presented the periodic table, only 63 elements were known.  Number of gaps for unknown elements were left in the table and the properties of these unknown elements were predicted on the basis of periodic law.  For example, gallium and germanium were not known when Mendeleev presented the periodic table. These elements were named eka-Aluminium and eka-Silicon. Modern Periodic Table  Moseley, suggested that basis of classification of elements should be the atomic numbers of the elements rather than the atomic masses of the elements.  He modified the periodic law.  Modified periodic Law: Chemical properties of elements are periodic function of their atomic numbers. 4  15‐01‐2025 Modern Periodic Table B non metals Si Transition As Ge metals Sb Te Inner transition Periods Groups or Families  Horizontal rows  Vertical columns  Members have the same # of principal energy  Members have the same number of valance electrons levels  Members of the group have similar chemical properties Rows are called “Periods”  Periods = rows  From left to right  What do elements in a row have in common? - the same number of electron shells  Every element in Period 1 (1st row) has 1 shell for its electrons (H & He)  All of the elements in period 2 have two shells for their electrons.  It continues like this all the way down the table. 5  15‐01‐2025 Columns are called Group What do elements in a group have in common? Same number of valence electrons (electrons in the outer shell) They share similar characteristics with the other elements in their family. Group 1: 1 valence electron Group 2: 2 valence electrons Group 13: 3 valence electrons Group 14: 4 valence electrons Group 15: 5 valence electrons Group 16: 6 valence electrons Group 17: 7 valence electrons Group 18: 8 valence electrons except He who has 2 The elements of the periodic table can be divided into three main categories: Non-metals, Metals, and Metalloids 6  15‐01‐2025 s-Block Group 1 - Alkali Metals Valance electron(s) 1 ( +1 ion) Most active metals Not found in nature by themselves Form stable compounds Can be obtained by electrolysis of fused salt. s-Block Group 2 - Alkaline Earth Metals Valance electrons 2 (+2 ion) Second most active metal Some are not found in nature by themselves. 7  15‐01‐2025 d-block (Transition Elements) (group 3 to 12) p-block Many positive oxidation numbers Valance electrons are in various energy levels -can lose electrons from more than one energy level Form colored ions in solutions Lanthanide Series: Shiny reactive metals Most found in nature Elements with atomic numbers 57 – 70. Actinides Series: Radioactive and unstable Most are man-made & not stable in nature Actinide series elements with atomic numbers 89 – 102. 8  15‐01‐2025 Problems 1. The horizontal rows in the periodic table are called 4. Which of the following elements is in the same family ______________. period as fluorine? a. silicon b. antimony 2. The vertical columns in the periodic table are called c. iodine ______________. group d. arsenic e. None of these. group 3. Elements in a ______________ have similar 5. Which of the following is a noble gas? chemical properties. a. polonium a. period b. astatine b. group c. krypton c. both a and b d. hydrogen d. neither a nor b e. francium 6. Of the s-block, p-block, d-block, and f-block of elements, which block contains most of the nonmetals? Answer: P‐Block 6. Applying dobernier triad rule, what would be the atomic mass of bromine if the the atomic mass of chlorine is 35.5 and iodine and iodine is 127. Answer: 7. Name the element which replaced eka-aluminium and eka-silicon proposed by Mendeleev. Answer: Gallium and Germanium Alkali metals 8.Name the Elements (group) for the following name: Alkaline earth metals Pnictogens Chalcogens Halogens Noble gases Lanthanides Actinides Rare-earth metals Transition elements Inner transition elements Main group elements 9  15‐01‐2025 Answers: Alkali metals - Group 1: Li, Na, K, Rb, Cs, Fr. Alkaline earth metals – The metals of group 2: Be, Mg, Ca, Sr, Ba, Ra. Pnictogens – The elements of group 15: N, P, As, Sb, Bi. Chalcogens – The elements of group 16: O, S, Se, Te, Po. Halogens – The elements of group 17: F, Cl, Br, I, At. Noble gases – The elements of group 18: He, Ne, Ar, Kr, Xe, Rn. Lanthanides – Elements 57–71: La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu. Actinides – Elements 89–103: Ac, Th, Pa, U, Np, Pu, Am, Cm, Bk, Cf, Es, Fm, Md, No, Lr. Rare-earth metals – Sc, Y, plus the lanthanides. Transition elements – Elements in groups 3 to 11 or 3 to 12 (the latter equalling the d-block). Inner transition elements – f-block elements. Main group elements – Elements in groups 1–2 or 13–18, except hydrogen. Who created the periodic table? Russian chemist Dmitri Mendeleev created the first periodic table in 1869. What is the rarest element? Astatine (𝐴𝑡) is the rarest naturally occurring element on Earth. What is the strongest element? Tungsten is the strongest natural metal in terms of tensile strength. What is the most interesting element? Gallium is a metal with a melting point below body temperature, low toxicity, and reactivity. What is the lightest element? Hydrogen (𝐻) is the lightest element on the periodic table. What is the organization of the periodic table? The periodic table has horizontal rows called periods and vertical columns called groups. What is the purpose of the periodic table? The periodic table organizes all known elements. How are elements in a group similar? Elements in a group have similar chemical and physical properties because they have the same number of outer electrons. 10  15‐01‐2025 Organization: The Modern periodic table is organized by increasing atomic number, while the table created by Russian chemist Dmitri Mendeleev was organized by increasing atomic weight. Elements: The first element on the periodic table is hydrogen (H) and the last is oganesson (Og). Prevalence: Hydrogen is the most common element in the universe, making up about 75% of the observable cosmos. Artificially created elements: Technetium (Tc) was the first element to be created artificially, in 1937. The name comes from the Greek word technetos, which means "artificial". Symbol letters: All the elements on the periodic table have symbols that are missing the letter J. Color coding: The modern periodic table uses color coding to help distinguish the properties of the atoms. Atomic size: Atomic size decreases across a period, even though the atomic number increases. IUPAC: The International Union of Pure Applied Chemistry (IUPAC) is the world authority on chemical terminology and nomenclature, including naming new elements. Halogens: The melting and boiling points of the halogens increase as you move down group 7, and the color gets darker. 11