# Question 8462f

Feb 21, 2017

Here's what I get.

#### Explanation:

Sodium is the only Group 1 element that gives a yellow flame colour.

A sodium atom in an unexcited state has the electron configuration $\text{1s"^2 "2s"^2 "2p"^6 "3s}$ but, within the flame, there will be many atoms with different excited states.

The bright orange-yellow flame colour results when electrons fall back from the $\text{3p}$ level to their normal $\text{3s}$ level.

The most likely candidate for the green gas is chlorine.

Sodium reacts vigorously with chlorine to form the white solid, sodium chloride.

The melting point of the ionic solid is 801 °C.

The equation for the reaction is

"2Na(s)" + underbrace("Cl"_2"(g)")_color(red)("green gas") → underbrace("2NaCl(s)")_color(red)("white solid")#

A sodium ion, $\text{Na"^"+}$, is just the right size to fit in the cavity of 15-crown-5, where becomes strongly attracted to the oxygen atoms.