How many of the following metals give oxides and nitrides when burnt in air? Be, Na, Mg, Ba, Sr, Li, K
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Among the alkali metals (Group 1), only Lithium reacts directly with nitrogen. All alkaline earth metals (Group 2) react with both oxygen and nitrogen when heated in air.
We need to identify which of the given metals react with both oxygen (O$_2$) and nitrogen (N$_2$) from the air upon burning.
Alkali Metals (Group 1):
- Li (Lithium): Lithium is unique in Group 1 as it reacts directly with nitrogen to form lithium nitride (Li$_3$N), in addition to forming lithium oxide (Li$_2$O) with oxygen. So, Li forms both.
- Na (Sodium): Primarily forms sodium peroxide (Na$_2$O$_2$) and does not react with nitrogen under these conditions.
- K (Potassium): Primarily forms potassium superoxide (KO$_2$) and does not react with nitrogen.
Alkaline Earth Metals (Group 2):
- All alkaline earth metals burn in air to form both oxides (MO) and nitrides (M$_3$N$_2$). This is a characteristic property of Group 2 elements due to their high reactivity.
- Be (Beryllium): Forms BeO and Be$_3$N$_2$.
- Mg (Magnesium): Forms MgO and Mg$_3$N$_2$.
- Sr (Strontium): Forms SrO and Sr$_3$N$_2$.
- Ba (Barium): Forms BaO and Ba$_3$N$_2$.
Counting the metals from the given list that form both oxides and nitrides:
Li, Be, Mg, Ba, Sr.
There are a total of 5 such metals.
