Balancing Equations (GCSE double award)

So, I've just gotten back a mock chemistry test (and it went alright, thank goodness) but I've gotten next to all the balanced equations wrong. Part of the problem is I don't understand when to do certain steps
The first question was balancing
Na + Br =NaBr
I put down Na+Br2 =Na2Br

Obviously, for anyone better than me at chemistry will realise this is wrong, I understand that it is wrong, just not why. Can anyone help? I've always used the "drop and swap method" for working out formula, and if Bromine is diatomic, why doesn't the two go to sodium?
Thanks for anyone who can answer

It is not Na2Br because although bromine is diatomic, the charge of bromine is -1 (it gains one electron). Always when dropping and swapping, you are looking at dropping and swapping the CHARGES, *NOT* the number of atoms.

Another example is Na and Cl. Na has a charge of +1 (it donates an electron) and Cl has a charge of -1 (it gains one electron). So dropping and swapping the CHARGES makes NaCl.

All halogens such as bromine and chlorine are diatomic, but they all have -1 charge which is what we are looking for when dropping and swapping.

So actually it is 2Na + Br2 = 2NaBr. Always in a balanced equations you put numbers in front of the reactants and products to ensure the number of atoms for each element is the same on the left and right of the equation, like what I did in the equation. 2 Na atoms on the left and on the right, and 2 Br atoms on the left and on the right.

I hope this has made sense.