A physical change is like freezing water and it turns into Ice.
Answer:
Kinetic energy: 
Velocity: 
Explanation:
From the equations of the photo-electric effect,
We know:
Where,
1.
is the Planck's constant which is 
2.
are the frequency of light emitted and threshold frequencies respectively.
3.
is the kinetic energy of the electrons emitted.
By fact, we come to know that the threshold frequency of Zn is 300nm
And also 
Where ,
1. 
is the speed of light 
2.
is the wavelength.
Thus,
Now to find velocity:
Answer:
• The Na atom is formed when the Na+ ion gains an electron.
• A Na+ ion has 10 electrons and a Na atom has 11 electrons.
• A sodium atom has one more electron shell than a sodium ion.
• A Na+ ion is formed when a Na atom loses an electron
When Br2 and NaF are mixed, no reaction would occur since Br cannot replace F in NaF which gives NaBr + F₂ as products. Hence, Fluorine is more reactive than Bromine. Hence, Br can't replace F.
<u>Explanation</u>:
- When two reactants Br2 and NaF are mixed, no reaction takes place since Br cannot replace F in NaF. By seeing the periodic table, the positions of the halogens in the periodic table, bromine is located way below fluorine.
- Bromine will not have sufficient energy to replace fluorine and so it will not have energy which is sufficient to join because of low reactivity. Among these fluorine represents the most reactive element among halogens.
- Some of you may think it is a single replacement reaction that gives NaBr + F₂ as products. But, according to the halogen reactivity, it decreases from top to down of the group. F is placed above Br. Hence, Fluorine is more reactive than Bromine. Hence, Br can't replace F.
Answer:
proton: positive
electron: negative
neutron: neutral
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