Find unmatched records in Access

So I have 2 tables in access. lets say table a and b.

both tables have same fields (employee id, last name, first name, and account number).

information in employee id, last name, and first name are the same.

the one who is different is the account number.

i would like to create a query that enables me to see those employees who have DIFFERENT account numbers in table a and b.

example: if jack has account number 1000 in table a and account number 2000 in table b, i want to him in the query. but if he has account number 1000 in both table a and b (match), then i dont want him in the query.

how do you achieve this? thanks!