The element is always present in a combustion reaction

Write the chemical formula for a compound that is made of an element from group 1 and an element from group 17

Can someone me with 3 and 4 plz. this is for masteries test.

Astable electron arrangement for an atom is one that does not easily change. how is this arrangement arrived at? a. valence electrons are transferred or shared to create a full outer shell of electrons. b. valence electrons are discarded into space to create a full outer shell of electrons. c. protons (positive charge) pair with valence electrons (negative charge) to create a strong bond. d. outer shells with valence electrons are transferred or shared.