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Ions of an element of group 1 participat...

Ions of an element of group 1 participate in the transmission of nerve signals and transport of sugars and aminoacids into cells. This element imparts yellow colour to the flame in flame test and forms an oxide and a peroxide with oxygen. Identify the element and write chemical reaction to show the formation of its peroxide. Why does the element impart colour to the flame?

Text Solution

Verified by Experts

Since the alkali metal imparts yellow colour in the flame test, it must be sodium.
It reacts with `O_2` to form sodium peroxide and sodium oxide.
`4Na + O_2 overset("Heat") underset("Sodium oxide")(2Na_2O)`
`2Na + O_2 to underset("Sodium peroxide")(Na_2O_2)`
`2Na_2O + O_2 overset("Heat")to underset("Sodium peroxide")(2Na_2O_2)`
So mainly sodium peroxide is formed.
Why does sodium impart yellow colour to the flame ? The ionization enthalpy of sodium is low. When sodium metal or its salt is heated in Bunsen flame , its outermost electron gets excited to higher energy levels by absorption of energy . When the excited electron returns to the ground state, it emits the extra energy which falls in yellow region of the visible spectrum . Therefore , sodium imparts yellow colour to the flame.
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