Atoms, Nuclei & Radioactivity Test - 10

Alpha particles, also called alpha rays or alpha radiation, consist of two protons and two neutrons bound together into a particle identical to a helium-4 nucleus. They are generally produced in the process of alpha decay, but may also be produced in other ways.

Let the initial amount of radon be  N_{0 ​}  and the amount left after  t  days be  N  which is equal to  N_{0 ​} /2

Given that 90% is left un-decayed after time 't '.
Hence, 10% decays in time 't '.
Initially assume that the amount of substance is 'x '
After time 't '10% is decayed.
i.e. Amount of substance left =0.9x
After further time 't 'another 10% is decayed.
i.e. 0.1 ×0.9x is decayed  
Leaving behind 0.81x.
Hence after time 2t we see that 0.19x has decayed, which is 19%.
 

Fission also results in the production of several neutrons, typically two or three. On the average, about 2.5 neutrons are released per unit and the energy of a neutron released per fission of a uranium atom are 2 MeV. 

An isotope is one of two or more forms of the same chemical element. Different isotopes of an element have the same number of protons in the nucleus, giving them the same atomic number, but a different number of neutrons giving each elemental isotope a different atomic weight.

Beta radiation ~ Stream of electrons (unit negative charge). Beta positive radiation is when a positron is emitted rather than an electron.
Gamma radiation ~ Electromagnetic radiation of very short wavelength = high photon energy.

Nuclear fusion is possible only between light nuclei as they become more stable by acquiring greater atomic number to form particles with intermediate mass. Nuclear fission is possible with heavy nuclei.

Like most stars, the sun is made up mostly of hydrogen and helium atoms in a plasma state. The sun generates energy from a process called nuclear fusion. During nuclear fusion, the high pressure and temperature in the sun 's core cause nuclei to separate from their electrons.

Nuclides which have the same number of  protons are called isotopes. When nuclides have the same mass, numbers are called isobars. When nuclides have same number of neutron are called isotones. When the elements have the same molecular formula but have different arrangements of atoms in space are called isomers.  

The hydrogen bomb is a nuclear weapon that uses a mixture of fission and fusion to produce a massive explosion.
The nuclear fission generates enough heat to initiate the nuclear fusion reaction. After that, the nuclear fusion releases enormous amounts of energy, making the hydrogen bomb a lot more powerful than an atomic bomb.

The hydrogen bomb is a nuclear weapon that uses a mixture of fission and fusion to produce a massive explosion.
The nuclear fission generates enough heat to initiate the nuclear fusion reaction. After that, the nuclear fusion releases enormous amounts of energy, making the hydrogen bomb a lot more powerful than an atomic bomb.
 

Since, from Rutherford-Soddy law, the number of atoms left after half-lives is given by
N=N₀ ​(1/2 ​)ⁿ
where, N₀ ​is the original number of atoms.
The number of half-lives, n= time of decay ​/effective half −life
Relation between effective disintegration constant (λ) and half-life (T)
λ=ln2/T ​
∴λ₁ ​+λ_{2 ​} = (​ln2/ T_{1 ​} )+ ​(ln2/ T₂ ​)
Effective half-life,
1/T ​=1/T₁ ​​+1/T₂ ​​=(1/1620)​+(1/810)​
1/T ​=1+2/1620 ​⇒T=540yr
∴n=T/540
∴N=N₀ ​(1/2 ​)^t/540 ⇒N/N₀ ​​=(1/2 ​)² =(1/2 ​)^t/540
⇒t/540 ​=2 ⇒t=2 ×540=1080yr

The chemical behavior of atoms is determined by the number and the configuration of the electrons in the atom. The number of protons in the nucleus determines the number of electrons in the atom.

The actual mass is always less than the sum of the individual masses of the constituent protons and neutrons because energy is removed when the nucleus is formed. This energy has mass, which is removed from the total mass of the original particles.