To calculate this,
We know that energy is 1 photon
E = hc/wavelenth
wavelength of 10.0 m
Solution:
h = 6.626 x 10^-34 Jsec
C = 2.9979 x 10^8 m/sec
E = 6.626 10^-34 * 2.9979 10^8 / 10 = 1.9864 10^-26J
Then, the number of photons is computed by:
n = 1000 / 1.9864 10^-26 = 5.04 10^28 photons
Na22 and Na24 are isotopes
The columns of the periodic table, also referred to as "groups" contain elements with similar reactive properties, due to these elements having a similar configuration of electrons in their outer shell.