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Alborosie
3 years ago
14

Finding energy and wavelength?

Chemistry
1 answer:
deff fn [24]3 years ago
3 0
The equation is
W = C/F
W= 3.00 x 10^8 m/sec
——————————
6.165 x 10^14 Hz
W= 4.87 x 10^-7 m

Energy is
E=hF
E= (6.626 x 10^-34 Jxsec )(6.165 x 10^14 Hz)
E= 4.085 x 10^-19 J




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Answer:

yup that's how you make friends with people on brainly

8 0
3 years ago
Suppose a laboratory wants to identify an unknown pure substance. The valence electrons of the substance's atoms feel an effecti
zalisa [80]

Answer:

  • The answer is the third option in the list:<em> It would have smaller atomic radii than Si and higher ionization energies than Si.</em>

Explanation:

The<em> effective nuclear charge</em> is that portion of the total nuclear charge that a given electron in an atom feels.

Since, the inner electrons repel the outer electrons, t<em>he effective nuclear charg</em>e of a determined electron is the sum of the positive charge (number of protons or atomic number) that it feels from the nucleus less the number of electrons that are in the shells that are are closer to the nucleus than the own shell of such (determined) electron.

Mathematically, <em>the effective nuclear charge (Zeff)</em> is equal to the atomic number (Z) minus the amount (S) that other electrons in the atom shield the given (determined) atom from the nucleus.

  • Zeff = Z - S.

Since, the valence electrons are the electrons in the outermost shell of the atom, you can find certain trend for the value Zeff.

Let's look at the group to which Si belongs, which is the group 14. This table summarizes the relevant data:

Element   Z   Group   # valence electrons     S                      Zeff = Z - S

C              6      14                      4                     6 - 4 = 2             6 -  2 = +4

Si             14     14                      4                     14 - 4 = 10         14 - 10 = +4

Ge           32     14                     4                     32 - 4 = 28       32 -28 = +4

Sn           50     14                     4                     50 - 4 = 46       50 - 46 = +4

Pb           82     14                     4                     82 - 4 = 78        82 - 78 = +4  

With that, you have shown that the valence electrons of the unknown substance's atoms feel an effective nuclear charge of +4 and you have a short list of 4 elements which can be the unknown element: C, Ge, Sn or Pb.

The second known characteristic of the unknown substance's atoms is that it has a <em>higher electronegativity than silicon (Si)</em><em>.</em>

So, you must use the known trend of the electronegativity in a group of the periodic table: the electronegativity decreases as you go down in a group. So, three of the elements (Ge, Sn, and Pb) have lower electronegativity than Si, which has left us with only one possibility: the element C. The valence electrons of carbon (C) atoms feel an effective nuclear charge of +4 and it carbon has a higher electronegativity than silicon.

Other two periodic trends attending the group number are the <em>atomic radii and the ionization energy</em>.

The atomic radii generally increases as you go from top to bottom in a group. This is because you are adding electrons to new higher main energy levels. So, you can conclude that the originally unknwon substance (carbon) has a smaller atomic radii, than Si.

The ionization energies generally decreases as you go from top to bottom in a group. This os due to the shielding effect: as seen, the effective nuclear charge of the atom's valence electrons remains constant, while the distance of the electrons from the nucleus increases (the valence electrons are farther away from the nucleus), which means the upper the element in a given group, the larger the ionization energy of the atoms.

With this, our conclusions about the unnkown substance are:

  • Since it has a higher electronegativity value than silicon (Si), it is right up of Si, and there is on only element possible element than can be (C).

  • Since, it is upper than silicon (Si), it would have smaller atomic radii.

  • Due to the shielding effect, it would have larger ionization energies.

  • The answer is the third option in the list: It would have smaller atomic radii than Si and higher ionization energies than Si.

6 0
3 years ago
The atomic number of an element is determined by the number of electrons in the nucleus of the atom.
iren [92.7K]
A
The number of electrons/protons is the one that determines the atomic number of an element.
7 0
3 years ago
Read 2 more answers
What is the molarity of aqueous lithium bromide if 25.0 mL of LiBr reacts with 10.0 mL of 0.250 M Pb(NO 3) 2
bixtya [17]

The molarity of aqueous lithium bromide, LiBr solution is 0.2 M

We'll begin by calculating the number of mole of Pb(NO₃)₂ in the solution.

  • Volume = 10 mL = 10 / 1000 = 0.01 L
  • Molarity of Pb(NO₃)₂ = 0.250 M
  • Mole of Pb(NO₃)₂ =?

Mole = Molarity x Volume

Mole of Pb(NO₃)₂ = 0.25 × 0.01

Mole of Pb(NO₃)₂ = 0.0025 mole

Next, we shall determine the mole of LiBr required to react with 0.0025 mole of Pb(NO₃)₂

Pb(NO₃)₂ + 2LiBr —> PbBr₂ + 2LiNO₃

From the balanced equation above,

1 mole of Pb(NO₃)₂ reacted with 2 mole of LiBr.

Therefore,

0.0025 mole of Pb(NO₃)₂ will react with = 2 × 0.0025 = 0.005 mole of LiBr

Finally, we shall determine the molarity of the LiBr solution

  • Mole = 0.005 mole
  • Volume = 25 mL = 25 / 1000 = 0.025 L
  • Molarity of LiBr =?

Molarity = mole / Volume

Molarity of LiBr = 0.005 / 0.025

Molarity of LiBr = 0.2 M

Learn more about molarity: brainly.com/question/10103895

3 0
3 years ago
How many moles are in 2.12g Cr2O3
ohaa [14]

Answer:

0.01395mol Cr2O3

Explanation:

the molar mass of Cr2O3 is 151.9904 g/mol

2.12g Cr2O3 x 1 mol/151.9904g = 0.01395mol Cr2O3

4 0
3 years ago
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