Element A is soft and can be cut with a knife. This is very reactive to air and cannot be kept open in air. It reacts vigorously with water. Identify the element from the following
(A) Mg
(B) Na
(C) P
(D) Ca
Answer.:
Let’s go through the options:
Mg:
- Mg is highly reactive and relatively soft
- It only reacts with air to form a protective oxide layer.
- It does not react with cold water
Na:
- Na is the most reactive metal in the reactivity series
- It reacts vigorously with water .
- It is also very soft and can be cut with a knife.
P:
- P is a highly reactive element and it is soft.
- It reacts vigorously with air and cannot be exposed to it without igniting
- It does not react with water .
- It is stored inside water to prevent exposure to air.
Ca.:
- Ca is a highly reactive metal
- It is relatively soft and can be cut with a knife
- It reacts with cold water and air to form hydroxides and oxides respectively.
So, the correct answer is (b) Na
