Classification of Elements
Importance of classification of elements:
→ The table in which elements are arranged scientifically according to their physical and chemical properties is called periodic table. Or The table in which elements are arranged according to group (vertical) and period (horizontal) is called periodic table. |
Q. Mendeleev's periodic principle:→ The physical and chemical properties of elements are the periodic functions of their atomic weights.
i.e. Mendeleev arrange elements in table according to their increasing atomic weight.
Q. Modern periodic principle (Moseley's periodic principle):→ The physical and chemical properties of elements are the periodic functions of their atomic number.
i.e. Moseley arrange elements in periodic table according to their increasing atomic number.
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Differencen between Mendeleev's and Moseley's Periodic table | |
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Do yourself
Q. Write the characteritic (feature) of Moseley's peridic table (Modern periodic table)?
Q. Write limitation of Mendeleev's periodic table?
Electronic configuration:→ The process of showing number of elements in different shell and subshell is called electronic configuration.
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Subshell and their capacity of accomodation of electron s = 2 electrons
p = 6 electrons
d = 10 electrons
f = 14 electrons
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| Group→ Period ↓ | ||||||||
| 1 | H 1s1 | He 1s2 | ||||||
| 2 | Li 1s22s1 | Be 1s22s2 | B 1s22s22p1 | C 1s22s22p2 | N 1s22s22p3 | O 1s22s22p4 | F 1s22s22p5 | Ne 1s22s22p6 |
| 3 | Na 1s22s22p63s1 | Mg 1s22s22p63s2 |
Al 1s22s22p63s23p1 | Si 1s22s22p63s23p2 | P 1s22s22p63s23p3 | S 1s22s22p63s23p4 | Cl 1s22s22p63s23p5 | Ar 1s22s22p63s23p6 |
| 4 | K 1s22s22p63s23p64s1 | Ca 1s22s22p63s23p64s2 | ||||||
Point to be remember
- Group :→ Group represents number of electrons in outermost cell. Or number of electrons in outermost cell represents group of elements.
- Period :→ Group represents number of cell. Or number of cell represents period of elements
- Block :→ Block represents last electron remains in subcell s or p or d or f. i.e. If last electron remains on s subcell than elements is s-block element and so on.
- Valency :→ The number of electron, an elements give or take or share during the chemical reaction is called valency of elements.It depends on valence electron ( the electron on outermost cell).
- ..........
- The elements which has 1, 2 or 3 elements in outermost cell, give outermost cell electrons during chemical reaction. So these elements have (+)ve valency.
- The elements which has 5, 6 or 7 elements in outermost cell, take electron during chemical reaction such that to fulfill its octe. So these elements have (–)ve valency.
- The elements which has 4 electrons in outermost cell, it share electron during chemical reaction.
As we move from left to right in periodic table following metallic and nonmetallic properties are found.
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Q. Position of Hydrogen in modrn periodic table?
→ Hydrongen has 1 electron in outermost cell so it put in IA group. Also it can take 1 electron like as VIIA group's elements, so it can be put in VIIA group.
Q. What are Lanthanides and Actinides?
→ The 14 elements Ce to Lu which are similar in characteristics are called Lanthanides and other 14 elements Th to Lr of same characteristics are called Actinites. These Lanthanides and Actinides are very similar to eachother but different from other elements so that they are put below the periodic table.
S-block elements :→ The elements whose last electrons remains on 's' sub-cell. Example: IA group and IIA group elements.
P-block elements :→ The elements whose last electrons remains on 'p' sub-cell. Example: IIIA to VIIIA group elements.
d-block elements :→ The elements whose last electrons remains on 'd' sub-cell. Example: Transition elements are d-block elements.
f-block elements :→ The elements whose last electrons remains on 'f' sub-cell. Example: Lanthanides and Actinides are f-block elements.
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