Electrons in an atom can be classified as core electrons and valence electrons. Valence electrons are those electrons which are present in valence shell and participates in bond formation. While, Core electrons are all remaining electrons which are not present in valence shell, hence not take part in bonding.
Atomic number of Selenium (Se) is 34 hence it has 34 electrons with following electronic configuration;
1s², 2s², 2p⁶, 3s², 3p⁶, 4s², 3d¹⁰, 4p⁴
From electronic configuration it is found that the valence shell is 4, and the number of electrons present in valence shell are 6. So,
Core Electrons = Total Electrons - Valence Electrons
Core Electrons = 34 - 6
Core Electrons = 28
Result:
There are 28 core electrons in Selenium.
Non-polar covalent
Explanation:
Propane is made up of non-polar covalent bonds and it can be expected to dissolve in hexane and to not dissolve in water.
Propane is an hydrocarbon gas.
It forms by sharing of electrons between two atoms with very low electronegativity differences.
This differences results in equal sharing of the shared electron. Therefore they form a non-polar covalent bond.
Water is a polar covalent compound and cannot dissolve compounds that are not polar like propane.
Propane will only dissolve in a like substance like hexane which is equally non-polar.
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Covalent compounds brainly.com/question/3109255
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Answer:
The correct answer is - D. Freezing point depression.
Explanation:
When rock salt is spread over snow-covered icy roads, it generates a liquid layer over it by melting from the surface thereby lowering or depression in the freezing point below the ice.
Therefore, due to this liquid layer comes into the contact with the ice present on the road and causes other ice to melts. This keeps on decreasing the volume of the ice on the road therefore, rock salts spread on the roads during a snowstorm.
Answer:
C8H20P4F8
Explanation:
Molecular formula is based off a ratio of the molecular formula's molar mass divided by the empirical formula's molar mass.
The molar mass of the empirical formula C2H5PF2 is 98.02g. We find this by adding the molar masses of all elements in the formula, multiplied by their subscripts.
2(12.01) + 5(1.01) + 30.97 + 2(18.99) = 98.02
We then divide the molecular molar mass by the empirical molar mass.
392.16/98.02 = 4
This tells us that the molecular formula has 4 times the mass of the empirical formula. Because mass comes from the elements in the formula, we multiply all the subscripts by 4 to get the molecular formula.
2x4 = 8
5x4 = 20
1x4 = 4
2x4 = 8
So the molecular formula is C8H20P4F8
Explanation:
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