An element x atomic number 16 reacts with an element Y atomic number 20 to form a compound i) position of the elements in the modern periodic table
ii) what type of bond will be formed between them ? give reason
iii) write the chemical formula of the compound

Element x has an atomic number of 16, it is sulphur.

Element Y has an atomic number of 20, it is calcium.

i) Sulphur is in Group VI, period 3 in the modern periodic table,

whereas calcium is in Group II, period 4 of the modern periodic table.

ii) Ionic bonds will form between them. This is because metals and non-metals (Cacium and sulphur) usually form ionic compounds where between the ions are held by ionic bonds (which are transferred electrons so that both elements can attain a stable status).

iii) CaS

each Calcium atom can lose 2 electrons to attain 8 outermost shell electrons, while each sulphur atom can gain the 2 electrons to attain 8 outermost shell electrons, where they will most be stable (octet). Hence, the atomic ratio of Ca and S is 1:1.

"record the time to complete a chemical reaction" would most likely be part of a lab procedure.