Make the equation equal on each side.
With number 1 it says the left side of the arrow has 1 Sn, 2 S, and 2 O.
The right has 1 Sn, 4 O, and 1 S.
So you have to balance the equation by putting numbers in front of the compounds.
SnS2 + O2 = SnO2 + SO2
SnS2 + 3 O2 = SnO2 + 2 SO2
Now there is 1 Sn, 2 S. and 6 O on each side. The large number in front of the compounds essentially multiplies it by that the subscript of that number. So with O2 it says there are 2 Oxygens. So they come in pairs. If you get 3 pairs of Oxygens there will be 6.
The same process goes with the rest of them too. Sometimes it takes a few guesses. Just figure them out like an algebra problem. Put the equal sign between them like I did. It maked it easier for me.
The answer is sublimation.
Sublimation is the chemical process whereby a solid turns into a gas without first becoming a liquid.
The word sublimation comes from the Latin word sublimare which means "raised to a higher status."
Examples of sublimation include surface layer of snow and ice turning into steam or fog without melting and dry ice which is the solid form of carbon dioxide which also undergoes sublimation.
The low temperature and sublimation makes dry ice an effective coolant or cooling agent . One of its main advantages is that it has a lower temperature than water ice and also does not leave any residue.
The first blank is Covalent compound
For the second blank, you are correct, though you may elaborate by specifying 'valence' electrons
