Chem 1st Paper Chap-3 (Test-2)

Explanation
Among the given options, Si (Silicon) is the only metalloid. Metalloids are elements that have properties of both metals and nonmetals. Silicon is a chemical element with atomic number 14 and it is a semiconductor, which means it can conduct electricity under certain conditions. Therefore, Si is the correct answer as it is the only metalloid among the given options.

Explanation
The correct answer is "উচ্চ চার্জ ঘনত্ব" (High charge density). This is because a high charge density in an ionic compound indicates a greater concentration of charge per unit volume. This leads to stronger electrostatic attractions between ions, resulting in a higher melting point and boiling point for the compound.

Explanation
The correct answer is 109.5. The bond angle in a molecule with a general formula of CnH2n is approximately 109.5 degrees. This is because the carbon atom forms four sigma bonds, resulting in a tetrahedral geometry. In a tetrahedral arrangement, the bond angles between the carbon and hydrogen atoms are approximately 109.5 degrees.

Explanation
পারমাণবিক সংখ্যা বৃদ্ধির সাথে সাথে নিষ্ক্রিয় যৌগের স্ফুটনাংক বৃদ্ধি পায়।

Explanation
CaCO3 is insoluble in water.

Explanation
The correct answer is F. This is because the question is asking for the name of the element that reacts with glass. The element that reacts with glass is fluorine (F).

Explanation
The coordination number of [Cu(en)2]2+ ion is 4. This is because each ethylenediamine (en) ligand forms two coordinate bonds with the central copper ion, resulting in a total of four bonds. The coordination number represents the number of ligands directly bonded to the central metal ion in a complex.

Explanation
The element Th (Thorium) is not a f-block element. The f-block elements are also known as the inner transition metals and they consist of the lanthanides and actinides. Thorium is part of the d-block elements, specifically in Group 3. Therefore, it is not considered a f-block element and is not a part of the f-block series.

Explanation
The correct answer is "বিকৃত চতুস্তলকীয়" (distorted tetrahedral). This means that the molecule SF4 has a distorted tetrahedral shape. A regular tetrahedron has four identical bonds and no lone pairs, but in SF4, there is one lone pair of electrons on the central sulfur atom, causing the shape to be distorted.

Explanation
None of the given options are neutral oxides. PbO2 and BaO2 are both peroxides, which are considered as acidic oxides. Fe2O3 is an oxide of iron, which is a metal and generally forms basic oxides. Therefore, none of the options can be classified as a neutral oxide.

Explanation
Zinc (Zn) is used as a protective coating for iron and steel to prevent corrosion. It acts as a sacrificial anode, meaning it corrodes in place of the iron or steel, thus protecting them from rusting. This process is known as galvanization. Therefore, applying a zinc coating or paste on iron or steel surfaces helps to protect them from corrosion, making it the correct answer.

Explanation
Among the given options, La (Lanthanum) is the rarest and most scarce mineral. It is a rare earth metal and is not commonly found in large quantities in nature. On the other hand, Zn (Zinc), Cu (Copper), and Ca (Calcium) are more abundant and commonly found minerals. Therefore, La is the rarest mineral among the given options.

Explanation
SF6 একটি হাইব্রিডাইজড মোলেকুল। এখানে, S অণুটি একটি কেন্দ্রীয় পাঁচটি p ওর্বিটাল এবং একটি d ওর্বিটাল ব্যবহার করে হাইব্রিডাইজড করে থাকে। সংকরায়নে, S অণুটির চারটি sp3 হাইব্রিড পাঁচটি p ওর্বিটালের সংকরায়িত ওর্বিটালের সাথে সংযুক্ত হয় এবং একটি d ওর্বিটালের সংকরায়িত ওর্বিটালের সাথেও সংযুক্ত হয়। সুতরাং, সঠিক উত্তরটি sp3d2।

Explanation
The correct order of the second ionization energy for N, O, and F is F > O > N. This means that it requires the most energy to remove a second electron from F, followed by O, and then N. This order is determined by the number of protons in the nucleus and the electron configuration of each element. F has the highest number of protons, making it the most difficult to remove an electron from. O has one less proton than F, making it easier to remove an electron. N has the least number of protons, making it the easiest to remove an electron.

Explanation
The elements in the f-block of the periodic table, including the 4f and 5f series, have incomplete electron configurations. Copper (Cu) belongs to the d-block and has a completely filled 3d orbital. Therefore, it does not have any f-orbital electrons and is not considered as having partial or complete 4f or 5f electron configurations.

Explanation
The correct answer is 2p. In the electron configuration of an atom, the first number represents the principal energy level (n) and the letter represents the sublevel. The sublevel 2p indicates that the electron is in the second principal energy level (n=2) and in the p sublevel.

Explanation
The correct answer is "চতুস্তলকীয়" which means "tetrahedral" in English. This term refers to a molecular shape in which there are four atoms or groups of atoms bonded to a central atom, arranged in a tetrahedral shape. In the case of NH4+, the central nitrogen atom is bonded to four hydrogen atoms, forming a tetrahedral shape.