1) A semimetal in group 8A
2)An alkali metal with a lower atomic number than barium
The Correct Answer and Explanation is:
Let’s break down the two parts of the question:
1) A semimetal in group 8A
Answer: The element you are referring to is astatine.
Explanation:
Group 8A of the periodic table is also known as the noble gases group, which includes elements like helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). However, astatine is a semimetal (also known as a metalloid) and is located in Group 7A (also called Group 17 or the halogens) in the periodic table, but it is sometimes considered as a semimetal due to its intermediate properties between metals and non-metals.
Astating (At) is the rarest naturally occurring halogen and exists in trace amounts in nature. While halogens are typically nonmetals, astatine shows some metallic characteristics, which is why it’s often classified as a semimetal. It has properties that are a mix of metals (such as good conductivity) and nonmetals (such as non-malleability).
2) An alkali metal with a lower atomic number than barium
Answer: The alkali metal you are referring to is sodium (Na).
Explanation:
Barium (Ba) is in Group 2A (alkaline earth metals), and its atomic number is 56. Alkali metals are located in Group 1A (excluding hydrogen) and include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr).
To answer the question, we need to find an alkali metal with a lower atomic number than barium. The alkali metals with lower atomic numbers than barium are lithium (Li), sodium (Na), and potassium (K). Since sodium (Na) has an atomic number of 11, which is lower than barium’s atomic number of 56, sodium is the correct answer.
Sodium is highly reactive, especially with water, and it is used in many industrial applications, including the production of soap, glass, and as a coolant in nuclear reactors. It is also essential to human life, as it helps regulate fluid balance and nerve function in the body.
Summary:
- Astatine is a semimetal, though not a member of Group 8A (noble gases), but in Group 7A (halogens).
- Sodium (Na) is an alkali metal with an atomic number of 11, which is lower than barium (56).