What do you call:

an expert in physics?
01.    A physicist
someone who works in the field of science?
02.    A scientist
a scientist who extracts metals from their ores?
03.    A metallurgist
a scientist who works in agronomy?
04.    An agronomist
an expert in chemistry?
05.    A chemist
an expert in mathematics?
06.    A mathematician
a doctor in biology?
07.    A biologist
a doctor concerned with children and their diseases?
08.    A pediatrician
a doctor who treats teeth?
09.    A dentist
One who deals with eyes?
10.    An optician
An expert in food consumption and dietetics?
11.    A dietician / dietitian
One who specializes in veterinary medicine?
12.    A veterinarian
An expert in the biological science of animals?
13.    A zoologist
A doctor who uses chemotherapy in the treatment of diseases?
14.    A chemotherapist
an expert in drugs, their composition, uses and effects?  (drug : medicine)
15.    A pharmacologist
one who is trained in pharmacy (a druggist)?
16.    A pharmacist
one who is an expert in economics?
17.    An economist
A medical doctor who treats patients' illnesses?
18.    A physician
An expert in poisons and the treatment of poisoning?
19.    A toxicologist
Someone who works in the field of electricity?
20.    An electrician