Which compound involves the formation of an electrovalent bond between a group 1 and a group 17 element?
KF forms by electron transfer from potassium (group 1) to fluorine (group 17), creating K^+ and F^-, an ionic bond. This follows from NCERT principle where the relation explains the outcome clearly for students in simple steps.
Ref: NCERT Chemistry Textbook for Class XI and XII, Chapter: Some Basic Concepts, Structure of Atom and Periodicity, Topic: Mole concept, atomic models and periodic trends.