1. Construct the Lewis Dot structure for sodium and magnesium. Compare the reactivity of these two elements .Explain your reasoning in terms of valence electrons.
2. Based on the periodic table, what do we now call the element Mendeleev called eka-manganese?
The Correct Answer and Explanation is :
- Lewis Dot Structure for Sodium and Magnesium:
- Sodium (Na):
Sodium (Na) is an alkali metal in Group 1 of the periodic table. It has one electron in its outermost shell (valence shell). The Lewis dot structure for sodium would be represented as:
[
\text{Na: } \bullet
]
where the single dot represents the one valence electron. - Magnesium (Mg):
Magnesium (Mg) is an alkaline earth metal in Group 2 of the periodic table. It has two electrons in its outermost shell. The Lewis dot structure for magnesium would be:
[
\text{Mg: } \bullet \bullet
]
where the two dots represent the two valence electrons. Reactivity Comparison: - Sodium: Sodium has one valence electron, which is easily lost to achieve a stable electron configuration (similar to the nearest noble gas, neon). This makes sodium highly reactive, especially with nonmetals like chlorine to form sodium chloride (NaCl). Sodium readily forms a positive ion (Na⁺) by losing its single valence electron.
- Magnesium: Magnesium, with two valence electrons, is also reactive but slightly less so than sodium. Magnesium tends to lose both of its valence electrons to form a Mg²⁺ ion. Its reactivity is still high, especially in reactions with nonmetals like chlorine to form magnesium chloride (MgCl₂), but it requires slightly more energy to remove two electrons compared to sodium, which only needs to lose one. Conclusion: Both elements are reactive because they readily lose electrons to achieve a stable electron configuration, but sodium is more reactive than magnesium due to having only one valence electron that is easily lost.
- Mendeleev’s “eka-manganese”:
The element Mendeleev called eka-manganese is technetium (Tc). Explanation:
In 1869, Dmitri Mendeleev, the Russian chemist who developed the periodic table, left gaps in his table for elements that had not yet been discovered. One of these gaps was placed below manganese (Mn), and Mendeleev predicted the existence of an element with similar chemical properties but with an atomic mass slightly higher than manganese. He named this hypothetical element eka-manganese, meaning “one beyond manganese” in Sanskrit. Technetium (symbol Tc), with atomic number 43, was later discovered in 1937 by Italian scientists Carlo Perrier and Emilio Segrè, fulfilling Mendeleev’s prediction. Technetium is a synthetic element, meaning it is not naturally abundant on Earth but can be produced artificially. It is classified as a transition metal, and it shares certain chemical characteristics with manganese, such as being a metal with a high melting point and similar oxidation states. The discovery of technetium was significant because it was the first element to be artificially produced in a laboratory, and it was the first element to be named after a prediction in the periodic table. Its name “technetium” comes from the Greek word “technetos,” meaning “artificial,” reflecting its synthetic origin. Technetium is used in a variety of applications, notably in medical imaging, as it is a key component of radiopharmaceuticals like technetium-99m, which is widely used in diagnostic imaging to visualize internal organs and tissues. Despite its usefulness, technetium is rare in nature, and its production requires specialized equipment.