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:
n(HCl)=1.96 mol
Explanation:
CH4+4Cl2⟶CCl4+4HCl
CCl4+2HF⟶CCl2F2+2HCl
With ideal yields we will end up with 4 moles of HCl.
With 70% yields on every stage
n(HCl)=0.7*0.7*4=1.96 mol
Definition of indirect evidence. : evidence that establishes immediately collateral facts from which the main fact may be inferred : circumstantial evidence.
Answer:
As the y-intercept increases, the graph of the line shifts up;
As the y-intercept decreases, the graph of the line shifts down
Explanation:
There are two ways to think about this problem. The first way would be the graphical approach:
- if we only change the y-intercept, this means we keep the same slope;
- y-axis is the vertical axis;
- if we change the point at which the line crosses the y-axis, we either shift it upward for a higher y-intercept or downward for a lower y-intercept.
Now, thinking algebraically, a line has the following equation in a general form:
The y-intercept is essentially obtained when x = 0, then:
y = b:
- if we increase b value, the y value increases, so the graph shifts upward;
- if we decrease b value, the y value decreases, so the graph shifts downward.
Answer:
a) Heterogeneous mixture (b) Homogenous mixture (c) Pure substance (d) Pure substance
Explanation:
Homogenous mixtures contains mixture of substances with similar proportions while Heterogenous mixture contains substances with a varying proportion.
