Periodic Table

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CHAPTER 5:

PERIODIC TABLE

Development of the Periodic Table
• i)

Substance exist: naturally in elemental form Example: Gold, Uranium as unstable compound Example: Radioactive compounds as stable compound (majority) How to know whether a substance is a compound OR an element?

ii)

iii)


• •

Grouping system: 1800: 31 elements identified 1865: 63 elements identified

Audi Majdan – DMC 101 – KLIUC

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Dmitri Mendeleev:
i)

ii) iii) iv)

Develop a system to group the elements Arranged elements by atomic weight Grouped elements by characteristics Able to predict future elements by using group characteristics



Henry Moseley: (i) Investigated: frequencies of X-rays produced by every elements (ii) Discovered: a relationship between the frequency and the atomic number (iii) Proposed: atomic number = number of electrons

The Periodic Table




The periodic table comprises of two main components: Group & Period Group: The elements placed in a column of the periodic table → 2 systems: 18 Groups or 8 Groups

Audi Majdan – DMC 101 – KLIUC

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Standard System Roman Numeral System 1 IA 2 II A 3 III B 4 IV B 5 VB 6 VI B 7 8 9 10 11 12 13 14 15 16 17 18 •

VII B VIII IB II B III A IV A VA VI A VII A VIII A

Transition Elements

Main groups can be designated as 'A' and 'B' with column number in Roman numerals. 3

Audi Majdan – DMC 101 – KLIUC

Group 1A 2A 6A 7A 8A

Elements Li, Na, K, Rb, Cs, Alkali metals Fr Be, Mg, Ca, Sr, Ba, Alkaline earth metals Ra Chalcogens O, S, Se, Te, Po Halogens F, Cl, Br, I, At Noble gases (inert or rare He, Ne, Ar, Kr, Xe, gases) Rn

Name



Period: The elements in a row of the periodic table → 7 Periods

Audi Majdan – DMC 101 – KLIUC

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Audi Majdan – DMC 101 – KLIUC

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Categories of elements:

(i) Metals (ii) Non-metals (iii) Metalloids
1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 1 5 1 6 1 18 7

Metal Nonmetal Metalloids Example: Metalloids: Boron (B), Silicon(Si), Germanium(Ge), Arsenic(As), Antimony(Sb), Tellurium(Te), Astatine(At) Audi Majdan – DMC 101 – KLIUC 6

Metals Alkali metals

Nonmetals

Inner transition Alkaline Transition Other Metalloids Other Noble Unknown elements earth Halogens elements metals nonmetals gases metals Lanthanides Actinides •



Elements in a Group have similar properties because they have the same type of electronic configuration of their atoms. Example: Li Na : 1s22s1 : 1s22s22p63s1 Group IA

3

11

Group IA: Lithium (Li), Sodium (Na) and Potassium (K) are all soft, very reactive metals He Ne : 1s2 (Exception) : 1s22s22p6

2

Group VIIIA

10


Group VIIIA: Helium (He), Neon (Ne) and Argon (Ar) are very non-reactive gasses

Audi Majdan – DMC 101 – KLIUC

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How do we get the name Periodic Table? If the elements are arranged in order of increasing atomic number, their chemical and physical properties show a repeating, or periodic pattern. Physical Properties Of Element • 1.

5 main physical properties of element:

Atomic size 2. Ionization energy 3. Electron affinity 4. Electronegativity 5. Oxidation Number 1. Atomic Size • •

Atomic size = radius of atom Down a column of the periodic table: atomic radius ↑, size of atom ↑

• REASON: • The addition of new shell, n ↑
Audi Majdan – DMC 101 – KLIUC 8



From left to right within a row of the periodic table: atomic radius ↓, size of atom ↓

• REASON: • The effective nuclear charge, Zeff ↑ Zeff = Z – S Z = proton number S = number of shielding electron •

Within a row: number of shielding electrons remains constant but the number of protons ↑

If (Zeff) on the valence electrons ↑ = electron will be attracted towards the nucleus → atomic radius ↓ Example: Audi Majdan – DMC 101 – KLIUC 9

For elements up to the 3p subshell


Number of shielding electrons for each elements: 12 (1s22s22p63s2) Element Z–S Zeff Al 1312 1+ Si 14 P 15 S 16 Cl 17 Ar 18

Atomic no 13

14- 15- 16-...
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