Question

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

which of these elements has the highest ionization energy?
radium
barium

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

which of these elements has the smallest atomic radius?
k
ca

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

which element is more chemically reactive?
ca
k

Explanation:

• Question 10: Ionization energy increases across a period and decreases down a group. Radium (Ra) and barium (Ba) are in Group 2. Radium is below barium in the group. So, barium has a higher ionization energy than radium.
• Question 11: Atomic radius decreases across a period. Potassium (K) and calcium (Ca) are in Period 4. Calcium is to the right of potassium. So, calcium has a smaller atomic radius than potassium.
• Question 12: Chemical reactivity of metals increases down a group and decreases across a period. Potassium (K) is in Group 1 and calcium (Ca) is in Group 2. Potassium is more reactive than calcium as Group 1 metals are more reactive than Group 2 metals in the same period.

Answer:

1. barium
2. Ca
3. K