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.
<span>Energy is absorbed and then released to form an emission line.
When electrons absorb energy they increase there energy level. This is only temporary and the excited electron then relaxes back down to its original energy level releasing energy.
The energy is released in form of EM radiation of a specific frequency depending on the element and how many energy levels the electron relaxes.
This forms an emission line.</span><span />
Answer:
1.88 M
Explanation:
The following data were obtained from the question:
Mole of NaCl = 0.47 mole
Volume of solution = 0.25L
Molarity =?
Molarity is defined as the mole of solute per unit litre of the solution. It can represented mathematically as:
Molarity = mole /Volume
Using the above formula, the molarity of the salt water solution can be obtained as follow:
Molarity = 0.47/0.25
Molarity = 1.88 M
