State Newlands' law of octaves. Give one merit and two limitations of it.

1. 1 · State the law. When elements are arranged in increasing atomic mass, every eighth element has properties like the first.
2. 2 · Example. Counting from lithium, the eighth element is sodium, and the two are alike.
3. 3 · Why 'octaves'. Like the notes of music, sa re ga ma pa dha ni, where the eighth note is sa again.
4. 4 · Merit. It was the first to show periodicity, using atomic mass as the basis.
5. 5 · Limitations.
   • It worked only up to calcium (atomic mass about 40)
   • After the noble gases were found, the ninth element matched the first
6. 6 · Close. So the octave idea was dropped, and Mendeleev's table followed.

Scoring tip: Name the musical comparison in one line; it shows you understand the word octave.