Pre-test เรื่อง พันธะเคมี

The correct answer is "พันธะที่เกิดจากการใช้เวเลนซ์อิเล็กตรอนร่วมกัน 1 คู่". This means that a covalent bond is formed when two electrons are shared between two atoms.

The reason why substances with low boiling points and melting points is because they have weak intermolecular forces between their molecules.

The given sequence represents the energy of element Z from the first to the eighth period. The values increase with each period, indicating an increase in the number of electrons in the element's outermost shell. The element Z belongs to the sixth period because the energy value for the sixth period is 13.333, which is the closest value to the given energy of the element. Therefore, the element Z has 6 valence electrons.

The explanation for the given correct answer is that both elements A and B have atomic numbers of 15 and 35 respectively. Based on the periodic table, element A with an atomic number of 15 belongs to the nitrogen group, which typically forms compounds with a triangular pyramid shape. Element B with an atomic number of 35 belongs to the bromine group, which typically forms compounds with a linear shape. Therefore, the chloride compounds of elements A and B should have a triangular pyramid shape and a linear shape respectively.

The correct answer states that metals have high electronegativity and it is difficult for them to lose electrons. This is because metals have a tendency to hold onto their electrons tightly due to their high electronegativity.

The correct answer is "พลังงานไอออไนเซชันสูง ขนาดอะตอมเล็ก อิเล็กโทรเนกาติวิตีสูง". This answer states that high ionization energy and small atom size are physical properties that can be used to describe the chemical properties of metals.

The correct answer is Y-B, A-Y, A-X. This is because Y has the highest EN value of 3.7, followed by A with an EN value of 3.0, and then X with an EN value of 2.7. B has the lowest EN value of 2.8. Therefore, the order of decreasing EN values is Y-B, A-Y, A-X.

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The correct answer is Y, X, Z. This is because the question asks for the arrangement of the compounds based on their bond energies. The bond energy is a measure of the strength of a chemical bond, and generally, higher bond energies indicate stronger bonds. In this case, Y has the highest bond energy of 200 kJ/mol, followed by X with 120 kJ/mol, and Z with 90 kJ/mol. Therefore, the correct arrangement is Y, X, Z, from highest to lowest bond energy.

The correct answer is CS2 > BF3 > CH4 > Cl2O. This is because the question is asking for the order of bond angles in the given molecules. The bond angle in CS2 is greater than that in BF3, and the bond angle in BF3 is greater than that in CH4. Finally, the bond angle in CH4 is greater than that in Cl2O.