Answer:
<h2>
total no. of electron present in Valency shell is called valency electron </h2><h2>___________________</h2>
<h2>valency shell is that in which last electron is present</h2>
Ok so first you need to figure out the energy of ONE photon with that wavelength. Using E=hc/lambda, you get E= 1.99 * 10^-20 J/photon. Now, how many photons do you need to add up to get to one kilojoule=1000 joules? 1000J / (1.99 * 10^-20 J/photon) = approximately 5 * 10^22 photons
hope this helps
The answer is to this question is c
Answer:
3
Explanation:
On the left side we have 3 Calcium atoms and 6 fluorine atoms
that means there need to be the same number on the right side
in the CaF2 molecules we already have 2 fluorine atoms so by multiplying with 3 we get 3 Ca and 6F
To know the number of atoms, it will be necessary to use the formula of avogadro. We calculate the number of moles then we can calculate the number of avogadro.
The molar mass of:
Phosphorus = 31g / mol
Mercury = 200 g / mol
Bismuth = 209 g / mol
Strontium = 87 g / mol.
The number of avogadro (N) is 6.023 10 ^ 23
n = m (mass) / M (molar mass)
number of atoms = n. N = m / M . N
number of phosphorus atoms = 5.14/31 . 6.023 10^23 = 9.98 10 ^ 22 atoms
Number of atoms of mercury = 2.16/200 . 6.023 10^23 = 6.5 10 ^ 21 atoms
Number of bismuth atoms = 1.8/209 . 6.023 10^23 = 5.18 10 ^ 21 atoms
Number of strontium atoms = 8.8 x 10-2 /87 . 6.023 10^23 = 6.09 10 ^ 20 atoms
