Question

Among alkali metals, radioactive element is ----- and half-life period of its longest lived isotope is ---
(A) Francium and 21 years
(B) Radium and 21 minutes
(C) Francium and 21 minutes
(D) Radium and 21 days​

Answer 1

Answer:

Option C is right.

Explanation:

First group elements are also called alkali metals because they form base or alkali on reaction with water.

The alkali metals are ,

• Lithium, L
• Sodium, Na
• Potassium, K
• Rubidium, Rb
• Cesium, Cs
• Francium, Fr

Usually , the element present lower in the periodic table are radio active.

So Francium is radio active and have a half life of 21 minutes.

NOTE:

• Radium , Ra is also radio active. But it belongs to the second group .

• Second group is also called alkaline earth metals because the hydroxides of some elements in group 2 are found in the earth surface.

• The half life of radium is 1600 years.

RADIO ACTIVITY:

• Radio activity is the phenomenon of releasing radiation due to disintegration of the element.

• Radio activity is measured in terms of Henry or Becquerel

HALF LIFE:

• Half life is the time period required for the disintegration of half amount of the element.

Answer 2

Answer:

option c hopes it helps u