Problem 71 - Chemistry The Central Science

Question

(a) Why is calcium generally more reactive than magnesium? (b) Why is calcium generally less reactive than potassium?

Step-by-Step Solution

Answer

(a) Calcium is generally more reactive than magnesium because it is located below magnesium in Group 2 of the periodic table. This means that calcium's outer electron shell is further from the nucleus, making it easier for calcium to lose its valence electrons compared to magnesium. (b) Calcium is generally less reactive than potassium because potassium is in Group 1, with only one valence electron, making it inherently more reactive than calcium which has two valence electrons. Additionally, the tendency of potassium to lose its valence electron is stronger due to its position in Group 1, despite the shorter distance between its nucleus and the outer electron shell.

Step 1: (Understand the periodic table)

(First of all, let's locate calcium (Ca), magnesium (Mg), and potassium (K) in the periodic table. Calcium and magnesium are both in Group 2, known as the alkaline earth metals, and potassium is in Group 1, known as the alkali metals. Calcium is located below magnesium in the same group, and potassium is located to the left of calcium in a different group. In general, elements in Group 1 are more reactive than those in Group 2, and reactivity increases as you move down a group. This is because elements in Group 1 have one valence electron, whereas elements in Group 2 have two. Additionally, as you move down a group, the outer electron shell is further from the nucleus, making it easier to lose the valence electrons in chemical reactions.)

Step 2: (Analyze the electron configurations)

(Let's examine the electron configurations of calcium, magnesium, and potassium to better understand their reactivity: Calcium (Ca): \([Ar] 4s^2\) Magnesium (Mg): \([Ne] 3s^2\) Potassium (K): \([Ar] 4s^1\) The reactivity of these elements is determined by the ease with which they can lose their valence electrons to form positive ions.)

Step 3: (a) Explain reactivity difference between calcium and magnesium)

(As mentioned earlier, both calcium and magnesium are in Group 2 and have two valence electrons. Since calcium is located below magnesium in the periodic table, its outer electron shell is further from the nucleus, and the attraction between these valence electrons and the nucleus is weaker. As a result, calcium can lose its valence electrons more easily than magnesium, making it more reactive.)

Step 4: (b) Explain reactivity difference between calcium and potassium)

(On the other hand, potassium is in Group 1 and has only one valence electron. This makes it inherently more reactive than calcium with its two valence electrons. Furthermore, potassium is also located above calcium in the periodic table, and its outer electron shell is closer to the nucleus. However, due to being in Group 1, the tendency of potassium to lose its valence electron is stronger than that of calcium, even with the shorter distance between the nucleus and the outer electron shell. So, potassium is generally more reactive than calcium.)