Question

protons

______

neutrons

______
82
pb
lead
207

Explanation:

Step1: Identify atomic number for protons

The atomic number of lead (Pb) is 82, and the atomic number is equal to the number of protons. So the number of protons is 82.

Step2: Calculate number of neutrons

The mass - number of lead here is 207. The mass - number is the sum of protons and neutrons. Let the number of neutrons be $n$. We know that mass - number = number of protons+number of neutrons. So $n=207 - 82$.
$n = 125$

Answer:

protons: 82

neutrons: 125