Question

1. use a periodic table to choose the best answer.

which element is more chemically reactive?
mg
na

1. use a periodic table to choose the best answer.

which of these elements has the smallest atomic radius?
be
b
u
c

Explanation:

Question 4

Step1: Analyze reactivity trends

In the periodic table, for metals, reactivity increases down a group and from right to left across a period. Sodium (Na) is in group 1 and magnesium (Mg) is in group 2. Sodium has one valence electron, and magnesium has two valence electrons. Sodium can lose its single valence electron more easily than magnesium can lose its two valence electrons.

Question 5

Step1: Analyze atomic radius trends

Atomic radius decreases across a period from left to right (due to increasing nuclear charge pulling electrons closer) and increases down a group. Beryllium (Be), boron (B), and carbon (C) are in the second period. Uranium (U) is a large - sized actinide. Among Be, B, and C, as we move from Be (group 2) to B (group 13) to C (group 14) across the second period, the atomic radius decreases.

Answer:

1. Na
2. C