To determine the type of matrix in which each element is zero, let's explore the concept of matrices:

• Null Matrix: A matrix is termed a null matrix or zero matrix if all of its elements are zero. This is the definition that best matches the description given in the question.
• Identity Matrix: An identity matrix is a square matrix in which all the elements of the principal diagonal are ones and all other elements are zero.
• Scalar Matrix: A scalar matrix is a diagonal matrix wherein all the elements on the diagonal are the same non-zero number, and other elements are zero.
• Square Matrix: A matrix is a square matrix if it has the same number of rows and columns. It does not require the elements to be zero.

From the above definitions, it is clear that a matrix where each element is zero is called a null matrix.

The correct answer is: null