Final answer:
The expression modeled by the arrangement of 16 negative tiles split into 2 groups of 8 negative tiles is '-8 - 8', which simplifies to '-16'.
Step-by-step explanation:
The question involves the concept of negative numbers and grouping in mathematics. The arrangement described in the question shows 16 negative tiles split into 2 groups of 8 negative tiles each. To express this arrangement as an algebraic expression, we simply denote the groups of negative tiles. Since we have two groups of eight negative tiles, the expression would be -8 - 8, which simplifies to -16.