Question

what is lanthanides and actinides?

Answer 1

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Lanthanoides and actinoids are a group of 28 elements that involve the filling of the f -orbitals. They are also known as the inner transition elements because they are present in between the transition elements. However, in the periodic table, they are are shown separately at the bottom. There are 14 lanthanoids and 14 actinoids that are listed in the periodic table. 
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The lanthanoids are characterised by filling of the 4f energy levels. They are extremely similar to each other in properties and were earlier thought to be similar elements. The elements form colored coloured ions, which also show magnetic properties. 
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The actanoids are characterised by filling of the 5f energy levels. These too, are similar to each other in properties and form coloured ions. 

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Answer 2

lanthanides which are start from 58 to 71 Lanthanide atomic number is 57 .Lanthanide which starts from 7th period so that full 7th period is lanthanide.
actinides which are start from 93 and ends of 103.
actinides atomic number is 92 actinides which start from 8 period so that the full 7th period is