Periodic classification of elements part 2..🎷
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Today we are going to look at the structure of the *modern periodic table* . Henry Mosley used atomic number instead of atomic mass to correct the remaining errors in Mendeleev’s periodic table. Henry Moseley arranged elements by increasing order of their atomic number modern periodic table. Henry Moseley divided the periodic table into four blocks s-block p-block d-block and f- block.
In the modern periodic table there are 118 boxes present , they occupies 118 elements.
* s-block elements.
1. s-block is made up of group 1 (ex. Sodium Na 2,8,1, potassium P) and group 2 ( magnesium Mg, calcium Ca.)
2. In s-block all Metal elements are present.
3. At normal temperature they are in solid state.
4. Group one is called as alkali metal ( alkali means when metal dissolves in water to form metal hydroxide Na + H2O = NaOH (aq)
aq means aqueous.
4. Group 2 is called as alkaline earth metal.
* p-block elements
1. Group 13 to group 18 elements are called as p-block element.
2. In P-block all types of elements are present such as metal, nonmetals and metalloid.
3. p-block shows all states such as solid, liquid ( at normal temperature bromine Br is in liquid state) and gaseous.
4. In p-block group 17 is called halogens, halogens means they prepare acid when react with hydrogen.ex. HCl, HBr.
5. In p-block inert gas /noble gas/ zero group elements are present in group 18. Ex. Helium He, neon Ne. Argon Ar.
6. In p- block the metalloid elements lie along the border of zig-zag line. Ex. Silicon Si, Arsenic As, Antimony Sb.
* Normal elements.
- Those elements having their only last orbit incomplete with electron and other orbits are filled with electron are called as normal elements.
- Ex. Sodium Na – 2,8,1.
- s-block elements and p-block elements are called as normal elements.
- Group 1, group 2 and group 13 to 17 are called as normal elements.
- These elements are chemically reactive elements.
- Place:- In modern periodic table they are placed to the extreme right and extreme left.
* ‘d’ – block elements
Transition elements
- Those elements having their last two orbits incomplete with electron and other orbits are filled with electron they are called as transition elements. Ex. Fe — 26 -Iron, electronic configuration 2, 8, 14, 2
- Group 3 to 12 elements are called as transition elements.
- Except Mercury (Hg) all other elements are in solid state.
- These are all heavy metals.
- These element prepare deep colourful compounds.
* ‘f’ – block elements
Inner transition elements
- These elements having their last three orbits incomplete with electron and last electron are present in ‘f’ shell they are called as inner transition elements.
- Ex lanthanides – La – 57 electronic configuration 2, 8, 18, 18, 9, 2.
- Position:- Inner transition elements are present below the periodic table, in third group and in 6th and 7th period in separate 2 series such as lanthanide and actinide series.
- In actinides series radioactive elements are present .
- Many of these are man made.
- Reactivity of actinid series is much more.
* Atomic size
Radius of atom indicates its size.
Atomic size is denoted by unit picometre pm.
Period:-As we go from the right to left in modern periodic table atomic size decreases. Because positive charge on nucleus increases by one unit and additional electron gates added on the same outermost shell due to the increased nuclear charge the electrons are pulled towards the nucleus of a greater extent and their by the size of atom decreases.
Group:-Atomic size goes on increasing in a group. Yes we go down a group new shell is added. Therefore distance between nucleus and outermost shell increases as a result atomic size increases.
Ex.
* Halogen group
- In modern periodic table group 17 is called as Halogen group.
- Ex. It contains fluorine F, chlorine Cl, bromine Br, iodine I.
- The physical state of these elements are – Fluorine and chlorine are in a gaseous state but bromine is in a liquid state and iodine is in a solid state.
* Inert gas elements
- Position:- In modern periodic table inert gas are present to the right side of the table in group 18.
- They are also called as Zero Group element, noble gas element.
- State:- At normal temperature they are in gaseous state.
- Reactivity:- They are non reactive because all shells are filled with electrons, in chemical reactions they cannot give , accept or share electrons.
📝 Small question, small answer, but very useful.
🥁 Write the names from the description.
1. The period with electrons in the shell K, L and M.
Ans:- third period
2. The group with valency zero.
Ans :- Group 18
3. The family of nonmetals having valency one.
Ans:- Halogen family
4. The family of metals having valency one.
Ans:- Group 1
5 . The family of metal having valency 2.
Ans :- Group 2
6 . The metalloids in the second and third period.
Ans :-Boron , silicon
7. Nonmetals in the third period.
Ans :-Phosphorus p , Sulphur S, chlorine Cl , and argon Ar.
8. To elements having valency 4.
Ans :- Carbon , silicon.
9. Three examples of noble gas.
Ans. – helium He neon Ne , argon Ar.
🎻 Write the name and symbol of the element from the description.
1. The atom having the smallest size.
Ans :- Hydrogen H.
2. The atom having the smallest atomic mass.
Ans :- Hydrogen H.
3. The noble gas with the smallest atomic radius.
Ans:- Helium He.
4. The most reactive nonmetal.
Ans :- Fluorine F.
5. The most electronegative atom.
Ans. – Fluorine F.
Exam link🔗 on this lesson.👇
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