Question

____ is the repetition of chemical properties according to atomic number. grouping the periodic table elemental classification periodicity 10. choose the best answer. what law revealed that the math did not work for all groups of elements, like the halogens? law of octaves mendeleevs law periodic law law of triads

Explanation:

• For the first question:
• Grouping: Just a general term for putting things together, not specifically about repetition of chemical properties by atomic number.
• The periodic table: It is a tabular arrangement of elements, not the concept of repetition itself.
• Elemental classification: A broad term for categorizing elements, not the repetition aspect.
• Periodicity: This is the correct term as it refers to the repetition of properties (including chemical properties) of elements when arranged in order of increasing atomic number.
• For the second question:
• Law of octaves: Proposed by Newlands. It stated that when elements are arranged in order of increasing atomic mass, every eighth element has similar properties. But it worked well for lighter elements like the first 16 elements but failed for heavier elements (e.g., halogens were not well - represented as per this law).
• Mendeleev's law (Periodic law as per Mendeleev): Arranged elements by atomic mass and predicted properties. It was more comprehensive than the law of octaves.
• Periodic law (in a general modern sense): Arranged by atomic number.
• Law of triads: Proposed by Dobereiner. Grouped elements in triads (groups of three) with similar properties based on atomic mass, but was very limited in scope compared to the law of octaves.

Answer:

1. Periodicity
2. law of octaves