1. 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

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

3. 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.

4. 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)

5. 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

6. 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 Cl, Br, I 3. Li, Na, K
2. John Newlands
(English chemist in 1864)  
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
N O F Na
P S Cl K

7. 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).

8. Mendeleev’s Periodic Table

9. 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

10. DIVISIONS OF P.T. CONTINUES
Metals, Nonmetals, Metalloids
s,p,d,f blocks s p d f

11. 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.

12. 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

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