Which of the following elements do not impart colour to flame ?
Ca, Mg, Li, Na, K, Rb
| A. |
Ca and Mg |
 |
| B. |
Li and Na |
| C. |
K and Rb |
| D. |
Na and K |
Ca and Mg don't impart colour to flame due to low value of atomic size which required high amount of energy to excite electron from ground state energy to excited state energy level.