A student writes Ba²⻠as the symbol for a barium ion. Explain what is incorrect about the symbol.
The Correct Answer and Explanation is:
The symbol Ba²⁻ written by the student is incorrect because barium ions do not carry a negative charge. Barium (Ba) is a metal found in Group 2 (alkaline earth metals) of the periodic table. Elements in this group have two electrons in their outermost shell, which they readily lose during chemical reactions to form positive ions (cations), not negative ones (anions).
Correct Symbol:
The correct symbol for a barium ion is Ba²⁺.
Explanation
The periodic table provides key information about how elements behave, particularly in terms of how they form ions. Barium (Ba) is in Group 2, which means it has two valence electrons. Atoms are generally more stable when they have a full outer electron shell, so barium tends to lose these two electrons to achieve the stable electron configuration of a noble gas (specifically xenon, in this case).
When an atom loses electrons, it becomes positively charged, because electrons are negatively charged. Since barium loses two electrons, it has two more protons than electrons, making the net charge +2. Therefore, the correct way to represent a barium ion is Ba²⁺.
On the other hand, anions are negatively charged ions that are formed when atoms gain electrons. This typically happens with nonmetals, such as oxygen or chlorine, not with metals like barium. The student’s notation of Ba²⁻ incorrectly suggests that the barium atom has gained two electrons, which is not chemically accurate for a metal.
Understanding ion charges is essential in writing chemical formulas and equations. Using the wrong charge can lead to incorrect compounds, misunderstood reactions, and errors in stoichiometric calculations. Therefore, it’s important to remember that metals such as barium always form positive ions, and their charges can be predicted from their group number in the periodic table. In conclusion, the correct ion symbol is Ba²⁺, not Ba²⁻.
