The answer is B. This is because Sodium has 1 valence electron and Fluorine has 7 valence electrons. All elements want 8 valence electrons so they may be stale, like the noble gases are. Hope this helps.
Speed in km/hr = 15 x 18
------------
5
= 54 km/hr.
Hope this helps!
The correct answer is b, 18 protons
Answer: D
Explanation:
the atom of the metal loses one electron which becomes delocalised and is attragted by the positive nucleus leading to formation of metallic bond.
Explanation:
It is given that,
Initial orbit of electrons, 
Final orbit of electrons, 
We need to find energy, wavelength and frequency of the wave.
When atom make transition from one orbit to another, the energy of wave is given by :

Putting all the values we get :

We know that : 
So,

Energy of wave in terms of frequency is given by :


Also, 
is wavelength
So,

Hence, this is the required solution.