Question

What are the elements in the $f$ block in period $7$ known as?

Answer 1

Hint : The elements in the periodic table are arranged as per the number of protons present in the nucleus of an atom. The atomic number goes on increasing from left to right. Elements present in the same group resemble in their properties.

Complete Step By Step Answer:
There is a total $7$ period in a periodic table. Each element present in the period has the same number of electron shells as the period number. The electrons are filled as $1s2s2p$ configurations. In the $7$ period the electrons are filled till the $f$ configuration and hence they belong in the $f -$ block. Elements of the $7$ period are called as actinides because they have an extended series of elements which is represented at the bottom of the periodic table. These elements start from the third group in the $7$ period and the first element is actinide hence the series is called actinide series. Elements in the actinide series are radioactive. These elements are highly reactive. The elements in these series have atomic numbers starting from $89$ to $103$ . These elements are highly electropositive. As their atomic number increases their ionic size decreases.

Note :
Elements in the actinide series show magnetic properties. These elements are silvery in nature. Elements in the third group in the ${6^{th}}$ period are called lanthanides.