This paper reports the impacts of spontaneous student grouping to develop young students' orthographic awareness in the process of learning Chinese characters. A mobile-assisted Chinese character forming game is used to assign each student a Chinese character component on their smartphones through a wireless network. Fifteen Singaporean students, all 3rd graders (10-year-old) studying Chinese as a second language (L2), were required to negotiate with their peers to form groups that could assemble eligible Chinese characters by using their respective components. The game process data and the transcriptions of focus group interviews were qualitatively analyzed in order to investigate the dynamics of student collaboration and competition during the games. In turn, the patterns of social interactions during the activities were identified, with a special focus on the varied impacts of the two grouping modes (allowing versus not allowing each student to join more than one group at one time) on the students' game habits.