A CLOSER LOOK AT THE ELEMENTS ◊ 92 elements are naturally occurring, the rest are man-made ◊ 25 elements are found and needed by our body - Major Elements: O, C,H,N - Minor Elements: Ca, P, K, S, Na, Cl, Mg - Trace Elements: Fe, I, Zn, Cr, Se, F, Co, Mo, Cu, Mn, V, Sn, Si, Ni ◊ A 50-Kg person’s body contains the ff. quantities of each element: 32.5Kg O 750g Ca 120g Na 9Kg C 500g P 95g Cl 5Kg H 175g K 25g Mg 1.7Kg N 125g S 2.5g Fe

EARLY SYMBOLS OF ELEMENTS (Used by Alchemists) Antimony Soap Lead Arsenic Gold Copper Mercury Silver Iron Carbon Fire Oxygen Tin Nitrogen Water

JONS JAKOB BERZELIUS INVENTED THE PRESENT SYSTEM OF REPRESENTING THE ELEMENTS USING THE FIRST OR ANOTHER LETTER OF THEIR LATIN OR ENGLISH NAME. Symbols are written with the first letter in upper case.

Symbols of elements from Latin name Natrium K Kalium Fe Ferrum Cu Cuprum Ag Argentum Sn Stannum Sb Stibium Au Aurum Hg Hydrargyrum Pb Plumbum *W Wolfram (German)

WAYS OF NAMING THE ELEMENTS From their discoverer/scientist – examples are Md, Lr, No, Es, Fm From the place of discovery – examples are Fr, Mg, Sc, Am, Bk, Eu From their properties – examples are

DEVELOPMENT OF THE PERIODIC TABLE SCIENTIST CONTRIBUTION/S 1. Johann Wolfgang Dobereiner (German chemist) Arranged chemically similar elements in groups of 3 known as the Dobereiner’s Triads Examples are 1. Ca, Sr, Ba 2. Cl, Br, I 3. Li, Na, K 2. John Newlands (English chemist in 1864)  1 2 3 4 Li Be B C Na Mg Al Si Formulated the Law of Octaves after noticing that the properties of elements if arranged in groups of 8 tend to recur periodically He Law of Octaves was found to be inapplicable after the element Ca 5 6 7 8 N O F Na P S Cl K

DEVELOPMENT OF THE PERIODIC TABLE (Con’t) SCIENTIST CONTRIBUTION/S 3. Dmitri Ivanovich Mendeleev (Russian chemist in 1870) Grouped the elements according to increasing atomic masses by following the Periodic Law – states that the properties of elements are the periodic functions of their atomic masses. Eventually created the first periodic table which had only 66 elements and had gaps that suggested the existence of other elements yet to be discovered. He predicted the elements Sc, Ga, Ge (ekasilicon) even before they were discovered. 4. Henry Moseley (English physicist in 1913) Grouped the elements according to increasing atomic numbers and made the modern Period Law – states that the chemical and physical properties of elements tend to vary periodically if the elements are arranged in increasing atomic numbers. He did this by observing the frequencies of X – rays emitted by atoms of elements were correlated with the sizes of their nuclear charges, which he then called the atomic number (Z).

Mendeleev’s Periodic Table

DIVISIONS OF THE P.T. PERIODS – are the horizontal arrangements of elements in the p.t. (7 rows) GROUPS/FAMILIES - are the vertical arrangements of elements in the p.t. a. Int’l Union of Pure and Applied Chem (IUPAC) version – 1 through 18 groups, new version b. Chemical Abstracts Service (CAS) version – Group A (I – VIII)  main or representative elements; s&p blocks - Group B (I – VIII)  transition elements; d & f blocks Inner Transition Outer Transition

DIVISIONS OF P.T. CONTINUES Metals, Nonmetals, Metalloids s,p,d,f blocks http://www.gordonengland.co.uk/elements/blocks.htm s p d f

4 Categories of Groups by Bohr A Group – main/representative elements composed of metals & nonmetals & metalloids where s & p sublevels are filled up partially or completely Group O Are nonmetals at the end of each period Also known as the noble or inert gases; they are very unreactive Have completely filled the s & p sublevels except He.

Categories by Bohr Continues B Group Are the transition elements Metals where the d sublevel is being filled up Inner Transition elements Metals where the f sublevel is being filled up 2 types: lanthanide -> 4f sublevel is filled -> rare earth metals actinide -> 5f sublevel is filled -> radioactive elements

The Different Main Elements Oxygen Group Alkaline earth metals Carbon Group Alkali Metals Boron group Nitrogen Group Halogen Group Noble Gases