Despite the importance of computer science education and computational thinking, there have been limited examples of computer science education at K-12 classrooms that authentically represents the work of computer scientists, especially programming. One reason is the lack of a measurable definition of computational thinking and a programming language friendly to K-12 students. In this case study, we used a text-based declarative programming language named SPARC to integrate computer science into the topic of the atomic structure. We also designed a rubric for the assessment of computational thinking that included two categories of abstraction and programming. We examined the experiences of two 8th-grade students representing those who have some experience with computer science and programming and those without any experience. The findings support the feasibility of integrating computer science and science and exposing middle-school students to text-based programming. We also discussed the pedagogical concerns in light of the students' challenges.