Chapter 11, Problem 11.50P

Explain the following statement. Although $\text{HC}\equiv {\text{C}}^{-}$ is more stable than ${\text{CH}}_2={\text{CH}}^{-}$, $\text{HC}\equiv {\text{C}}^{+}$ is less stable than

${\text{CH}}_2={\text{CH}}^{+}$.