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4 years ago

Why is light emitted when electrons move from the excited state to the ground state????

1 answer:

Montano1993 [528]4 years ago

8 0

The most common way for electrons to move to an excited state is by absorption of electromagnetic radiation. When an electron absorbs this radiation, it takes in the energy that the wave contains and this causes it to move to a higher energy state. They come back to ground state at the first possible opportunity because in the excited state they have lots of potential energy. Electrons can make different jumps in energy levels when it loses this potential energy (ie. it can go directly to the ground state, or it can go to lower energy levels and then the ground state). When they move to lower energy levels, the electrons emit the electromagnetic radiation that was absorbed - the frequency of the waves emitted depends on the electron's jumps between energy levels as it returns to ground state.

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What does the most accurate clock tell us

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4 years ago

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Specify which atoms, if any, bear a formal charge in the Lewis structure given and the net charge for the species.

ozzi

Answer :

Formal charge on C: (-1)

Formal charge on N: (0)

Net charge: (-1)

Explanation :

First we have to determine the Lewis-dot structure of $CN^-$ .

Lewis-dot structure : It shows the bonding between the atoms of a molecule and it also shows the unpaired electrons present in the molecule.

In the Lewis-dot structure the valance electrons are shown by 'dot'.

The given molecule is, $CN^-$

As we know that carbon has '4' valence electrons and nitrogen has '5' valence electrons.

Therefore, the total number of valence electrons in $CN^-$ = 4 + 5 + 1= 10

According to Lewis-dot structure, there are 6 number of bonding electrons and 4 number of non-bonding electrons.

Now we have to determine the formal charge for each atom.

Formula for formal charge :

$\text{Formal charge}=\text{Valence electrons}-\text{Non-bonding electrons}-\frac{\text{Bonding electrons}}{2}$

$\text{Formal charge on C}=4-2-\frac{6}{2}=-1$

$\text{Formal charge on N}=5-2-\frac{6}{2}=0$

Net charge = -1 + 0 = -1

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4 years ago

When scientists look at these examples, what do they know about the atoms? Carbon-12 Carbon-14

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3 years ago

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If 30.0 mL of Ca(OH)2 with an unknown concentration is neutralized by 40.0 mL of 0.175 M HCl, what is the concentration of the C

Over [174]

Answer:

Concentration of Ca(OH)₂:

0.117 M.

Explanation:

How many moles of HCl is consumed?

Note the unit of concentration: moles per liter solution.

$c(\text{HCl}) = 0.175\;\text{M} = 0.175\;\text{mol}\cdot\textbf{L}^{-1}$ .

Convert milliliters to liters.

$V(\text{HCl})=40.0\;\text{mL} = 0.0400\;\text{L}$ .

$n(\text{HCl}) = c(\text{HCl})\cdot V(\text{HCl})= 0.175\;\text{mol}\cdot\text{L}^{-1} \times 0.0400\;\text{L}= 7.00\times 10^{-3}\;\text{mol}$ .

How many moles of NaOH in the solution?

Refer to the equation. The coefficient in front of Ca(OH)₂ is 1. The coefficient in front of HCl is 2. In other words, it takes two moles of HCl to neutralize one mole of Ca(OH)₂. That $7.00\times 10^{-3}\;\text{mol}$ of HCl will neutralize only half that much Ca(OH)₂.

$\displaystyle n(\text{Ca}(\text{OH})_2)=\frac{1}{2}\;n(\text{HCl}) = 3.50\times 10^{-3}\;\text{mol}$ .

What's the concentration of the Ca(OH)₂ solution?

Concentration is the number of moles of solute per unit volume.

$\displaystyle c(\text{Ca}(\text{OH})_2) = \frac{n(\text{Ca}(\text{OH})_2)}{V(\text{Ca}(\text{OH})_2)} = \frac{3.50\times 10^{-3}\;\text{mol}}{0.0300\;\text{L}}=0.117\;\text{mol}\cdot\text{L}^{-1}$ .

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3 years ago