Any trick to remember valancy of radicles? plz tell me..

The number of waves in the third orbit of hatomis(1) 1(2) 2(4) 3(3) 4​

m. in two moles of acetaldehyde(ch cho) calculate the followinga. number of moles of carbonb. number of moles of hydrogenc. number of moles of oxygend. number of molecules of acetaldehyde(ans.: a. 4 mol, b. 8 mol, c. 2 mol,d. 12.044 x 10molecules)​

Name the metals which occur as carbonate