Z=15 1s²2s²2p⁶3s²3p³ vậy cần thêm 3 để đqtj quy tắc octet 

Z=1 1s¹ còn thiếu 1 để đạt quy tắc octet

By combining online and in-person instruction, blended learning gives students greater autonomy. They have access to a variety of resources, can readily revisit lessons, and learn at their own pace. Additionally, this method improves communication in both the classroom and online environments . Teachers are better able to monitor student development and modify their teaching accordingly. Above all, it fosters the development of IT skills and self-learning, two things that are critical in the digital age.