The metallic character of elements increases as you move down a group and decreases as you move across a period.
In a group, metallic character increases as the atomic size increases, resulting in a weaker attraction between the valence electrons and the nucleus.
In a period, metallic character decreases as the effective nuclear charge increases, making it more difficult to lose electrons.
Thus, the metallic character decreases from K to Be across the period, and increases from Be to Ca down the group.
Therefore, the correct order of metallic character is: \[ \text{K} > \text{Ca} > \text{Be} \]
Let one focus of the hyperbola $ \frac{x^2}{a^2} - \frac{y^2}{b^2} = 1 $ be at $ (\sqrt{10}, 0) $, and the corresponding directrix be $ x = \frac{\sqrt{10}}{2} $. If $ e $ and $ l $ are the eccentricity and the latus rectum respectively, then $ 9(e^2 + l) $ is equal to:
The largest $ n \in \mathbb{N} $ such that $ 3^n $ divides 50! is: