4 is D. 5 is C. 6 is D i guess. 7 is D.
Where is chemical equation?
Answer:
Conduction is the transfer of thermal energy through direct contact. Convection is the transfer of thermal energy through the movement of a liquid or gas. Radiation is the transfer of thermal energy through thermal emission.
2Na^+ and S^2-
(sodium cation and sulfide anion)
There are 2 valence elcetrons
