Question

select all the correct answers. which statements about the structure of the periodic table are true? the periodic table has an irregular shape because it has more periods than groups. the inner transition elements are placed at the bottom of the periodic table for easy viewing. the periodic table has horizontal groups and vertical periods, giving it a regular rectangle shape. the distribution of electrons in energy levels is responsible for the shape of the periodic table. nonmetals take up more than half the area of the periodic table.

Explanation:

1. Analyze the first statement: The periodic table's shape isn't due to more periods than groups. The number of periods (7) and groups (18) doesn't justify an irregular shape this way, so this is false.
2. Analyze the second statement: Inner transition elements (lanthanides and actinides) are placed at the bottom (f - block) for easier viewing (to keep the table compact), so this is true.
3. Analyze the third statement: The periodic table has vertical groups and horizontal periods. Also, it's not a regular rectangle (due to f - block placement), so this is false.
4. Analyze the fourth statement: The electron configuration (distribution in energy levels) determines the arrangement (periods based on principal quantum number, groups on valence electrons), so it's responsible for the shape, this is true.
5. Analyze the fifth statement: Metals (not non - metals) take up more than half the periodic table, so this is false.

Answer:

B. The inner transition elements are placed at the bottom of the periodic table for easy viewing.
D. The distribution of electrons in energy levels is responsible for the shape of the periodic table.