I would say the energy has to be decreased by 87 kj because the bonding is held together by 87 kj so removing that should prevent the bonding from taking place or reverse it I believe. In other words, a certain amount of energy is required to hold the bond together and in the absence of that energy, the bonding will not take place.
First shell from the nucleus can have a maximum of 2 electrons ! hope this helped
Not sure how in depth or what level of particles but I will go as deep as I know. The matter that makes up the world is comprised of 12 particles which are known as fermions. There are 12 fermions which are made up of 6 quarks (up, charm, top, Down, Strange, Bottom) 3 electrons (electron, muon, tau) and three neutrinos (e, muon, tau). Technically, only the up quark, down quark, electron, and electron neutrino are necessary to create all known matter since others would simply be very unstable and decay into those particles. The other type of particles are known as Bosons. These particles transmit forces and all sorts of different interactions. I have included a photo from online which describes the main characteristics of each elementary particle.
Explanation:
a) 3Pb(NO3)2 + Al2(SO4)3 ---> 3PbSO4 + 2Al(NO3)3
Double displacement
b) 2Cl2 + 3O2 ---> 2Cl2O3
Synthesis
c) 2Fe2O3 + 3C ---> 4Fe + 3CO2
single displacement