Question

the scarcest natural element is ______.
astatine
uranium
francium
question 10
______ was the key element in giving the modern periodic table its shape.
actinium
einsteinium
astatine

Explanation:

For the first question: Francium is the scarcest natural element, as it has an extremely short half-life and only tiny amounts exist naturally.
For Question 10: Actinium is the key element that led to the placement of the actinide series, which defined the modern periodic table's shape by creating the bottom row of inner transition metals.

Answer:

1. francium
2. Actinium