what is the full electron configuration of lead?

According to your convention, the electron configuration of lead is
Pb: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 6p² 5d¹⁰ 4f¹⁴

However, the more widely-accepted electron configuration of lead is
Pb: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p²

Walk your way through the periodic table:
The first period to He gives 1s2
The second period to NE fills 2s2 and 2p6
The third period to Ar fills 3s2 3p6
The 4th period to Kr fills 4s2 3d10 4p6
The 5th period to Xe fills 5s2 4d10 5p6
From Cs to Pb fills 6s2 4f14 5d10 6p2

So the full electron configuration is: 
1s2 2s 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p2