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.
Answer:
c. CH4 < NH3 because the NH bond is more polar than the CH bond.
Explanation:
Actually, the electronegativity difference between carbon and hydrogen is just about 0.4. This meager difference in electronegativity corresponds to a nonpolar bond between the two atoms.
However, the electronegativity difference between nitrogen and hydrogen is about 0.9. This larger electronegativity difference corresponds to the existence of a polar covalent bond between the two atoms.
Hence the N-H bond is significantly polar unlike the C-H bond. This implies that CH4 molecules are only held together by weak dispersion forces while NH3 molecules are held together by stronger dipole-dipole interactions and hydrogen bonds.
H^+(aq) + OH^-(aq) ---> H2O(l)
<span>Na^+ and ClO4^- are the spectator ions.</span>
Answer:
The chemist needs to react 40 g of sulfur with 60 g of oxygen to make 100 g of sulfur trioxide.
Explanation:
2S (s) + 3O₂ (g) → 2SO₃ (g)
64g + 96g → 160 g
32g + 48g → 80 g
x + y → 100 g
1 mol SO₃ ___ 80g
n _______ 100g
n = 1.25 mol SO₃
1 mol S ___ 32 g
1,25 mol S __ 40 g
1 mol O₂ ___ 32 g
1,875 mol O₂ ___ 60 g
