Hướng dẫn giải Bài 2 (Trang 111 SGK Hóa học 12)

Cation <math xmlns="http://www.w3.org/1998/Math/MathML"><msup><mi>M</mi><mo>+</mo></msup></math> có cấu hình electron ở lớp ngoài cùng là <math xmlns="http://www.w3.org/1998/Math/MathML"><mn>2</mn><msup><mi>s</mi><mn>2</mn></msup><mn>2</mn><msup><mi>p</mi><mn>6</mn></msup></math>. <math xmlns="http://www.w3.org/1998/Math/MathML"><msup><mi>M</mi><mo>+</mo></msup></math> là cation nào sau đây ? A. <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>A</mi><msup><mi>g</mi><mo>+</mo></msup></math>               B. <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>C</mi><msup><mi>u</mi><mo>+</mo></msup></math>               C. <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>N</mi><msup><mi>a</mi><mo>+</mo></msup></math>                  D. <math xmlns="http://www.w3.org/1998/Math/MathML"><msup><mi>K</mi><mo>+</mo></msup></math> Hướng dẫn giải: Chọn C. Cấu hình electron của Na (Z = 11) : <math xmlns="http://www.w3.org/1998/Math/MathML"><mn>1</mn><msup><mi>s</mi><mn>2</mn></msup><mn>2</mn><msup><mi>s</mi><mn>2</mn></msup><mn>2</mn><msup><mi>p</mi><mn>6</mn></msup><mn>3</mn><msup><mi>s</mi><mn>1</mn></msup></math>                Cấu hình electron của <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>N</mi><msup><mi>a</mi><mo>+</mo></msup></math> <math xmlns="http://www.w3.org/1998/Math/MathML"><mfenced><mrow><mi>N</mi><mi>a</mi><mo>→</mo><mi>N</mi><msup><mi>a</mi><mo>+</mo></msup><mo> </mo><mo>+</mo><mn>1</mn><mi>e</mi></mrow></mfenced></math>: <math xmlns="http://www.w3.org/1998/Math/MathML"><mn>1</mn><msup><mi>s</mi><mn>2</mn></msup><mn>2</mn><msup><mi>s</mi><mn>2</mn></msup><mn>2</mn><msup><mi>p</mi><mn>6</mn></msup></math>