A.Sodium is an element and it' symbol is Na
b.water is a compound because it consist of hydrogen and oxygen's symbol is H2O

c. ammonium is a compound and it's formula is NH4
d. calcium carbonate is a compound and it's formula is CaCo3 
e.methane is a compound and its formula is CH4
f. lead is a element and it's symbol is Pb

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A. Sodium is an element b. Water is a compound c. Ammonium is a radical compound d. Calcium carbonate is a compound e. Methane is a compound f. Lead is an element