Yes, barium is indeed more reactive than calcium.
Understanding Metallic Reactivity
Reactivity in metals, especially for elements like barium and calcium, is primarily determined by their metallic character. Metallic character refers to an element's propensity to lose electrons and form positive ions. The easier an atom can lose its valence electrons, the more metallic and, consequently, more reactive it is.
Barium and calcium are both alkaline earth metals, located in Group 2 of the periodic table. As you move down a group in the periodic table, the metallic character generally increases. This trend is due to several factors:
- Increasing Atomic Size: As you go down a group, the number of electron shells increases, leading to a larger atomic radius. Barium atoms are significantly larger than calcium atoms.
- Decreased Nuclear Attraction: With more electron shells, the outermost valence electrons are further from the positively charged nucleus and experience less attraction. This effect is further amplified by increased electron shielding from inner electron shells.
- Lower Ionization Energy: Consequently, less energy is required to remove these outermost electrons. The ionization energy of barium is lower than that of calcium, meaning it takes less energy to form a positive ion.
These factors combine to make barium more likely to lose electrons and participate in chemical reactions, especially compared to calcium.
Reactivity Comparison: Barium vs. Calcium
The difference in reactivity between barium and calcium can be observed in their reactions with other substances, such as water. Barium reacts more violently with water than calcium does, readily forming barium hydroxide and hydrogen gas. This pronounced reaction highlights barium's greater metallic character and its stronger tendency to give up electrons.
Here's a quick comparison of their relevant properties:
| Property | Calcium (Ca) | Barium (Ba) | Implications for Reactivity |
|---|---|---|---|
| Atomic Number | 20 | 56 | Barium is below calcium in Group 2. |
| Atomic Radius | Larger than elements above it in Group 2 | Larger than calcium | Larger size means valence electrons are further from nucleus. |
| Ionization Energy | Relatively low, but higher than barium | Lower than calcium | Easier to lose electrons. |
| Metallic Character | High | Higher than calcium | Greater tendency to form positive ions. |
| Reactivity with Water | Reacts steadily to produce hydrogen gas and calcium hydroxide | Reacts vigorously/violently to produce hydrogen gas and barium hydroxide | Barium is more reactive. |
Key Takeaways on Reactivity
- Electron Loss: Barium's larger atomic size and weaker nuclear attraction to its valence electrons mean it requires less energy to lose them.
- Metallic Character: A higher metallic character directly correlates with greater reactivity in metals.
- Periodic Trends: The increase in reactivity down a group for alkaline earth metals is a consistent periodic trend driven by atomic size and ionization energy.
In conclusion, barium exhibits a stronger metallic character than calcium due to its position further down Group 2 of the periodic table, leading to a higher propensity to lose electrons and, consequently, greater chemical reactivity.
