Which of the nitrates on strong heating leaves the metal as the residue?

Explain the significance of sodium,potassium,magnesium,and calcium in biological fluids.

The electronic configuration of a metal $M$ is $1s^2, 2s^2 2p^6, 3s^1$. The formula of its oxide will be

Identify $X$ and $Y$, respectively in the following reactions:

State True or False:
$(1)$ Half-life of $^{223}Fr$ is $21 \ s$.
$(2)$ $Li^{+}$ has a high hydration enthalpy and therefore its salts are usually hydrated in nature.
$(3)$ Among all the alkali metals,only $Na$ can react with nitrogen of air and form a nitride.
$(4)$ Except $LiF$,other halides of $Li$ are soluble in water.

Which metal does not give the following reaction: $M + \text{water or steam} \to \text{oxide} + H_2 \uparrow$?