Radioactive element poisoning

Radioactive elements:A radioactive element is one with an unstable nucleus, which radiates alpha, beta or gamma radiation and gets converted to a stable element.

An element will undergo decay if:

1. It has more than 83 protons.
2. The ratio of protons to neutrons is very close. For example, Carbon, having 6 protons and 6 neutrons (therefore having a 1:1 ratio of protons and neutrons) is a very stable atom. On the other hand, Bismuth, an unstable atom, has 126 neutrons and 83 protons, giving it a 1.52:1 ratio.
3. Nuclides containing certain numbers of protons or neutrons (2, 8, 20, 50, 82, and 126) are more stable than others.
4. Nuclides with even numbers of both protons and neutrons and more stable than those with odd numbers of

Radioactivity:It's a spontaneous and random phenomenon whereby nuclei of certain chemical elements like Uranium, radiate gamma rays (high frequency electromagnetic radiation), beta particles (electrons or positrons) and alpha particles (Helium Nuclei).

Key factor lies in the nucleus of an element:To understand radioactivity, we need to explore the structure of an atomic nucleus. Every nucleus contains neutrons as well as protons. Neutrons are neither positively charged, nor negatively charged, they are neutral particles. Protons are positively charged. And as we know that like charges repel each other while unlike charges attract each other. In the nucleus, protons and neutrons are cramped together in a really very small space.

The protons in the nucleus, all being positively charged, repel each other! So if all the protons repel each other, how does the nucleus stay glued together and remain stable? It is because of the 'Nuclear Force'.

This force is more stronger than the electromagnetic force, but the range of this force is only limited to size of the nucleus, unlike electromagnetic force whose range is infinite. This nuclear force acts between the protons and neutrons, irrespective of the charge and it's always strongly attractive. However, it has limitations of range. So, in the nucleus, there is a constant tussle between the repelling electromagnetic coulomb force of protons and the attractive strong nuclear force.

In a nucleus like Uranium, which has almost 92 protons, coulomb repulsive force becomes too much for the nuclear force to contain. Subsequently, the nucleus is very unstable and radioactive decay occurs and Uranium decays into a more stable element. Such an unstable nucleus like Uranium, when gently tapped by a neutron, splits up into two other nuclei through nuclear fission, releasing tremendous amount of energy in the process! This is the principle on which nuclear energy and nuclear weapons are based.

A full explanation of radioactivity can only be given, if we plunge deep into quantum physics and elementary particle physics.

Types of Radioactive Decay:This decay may occur in any of the following three ways:

alpha decay, in which a nucleus emits an alpha particle, which consists of 2 neutrons and 2 protons and is equivalent to a helium nucleus; beta-minus decay, in which an electron is emitted along with an antineutrino (not shown); gamma decay, in which a nucleus gets rid of its excess energy by emitting a gamma ray photon; and proton decay, the release of a single proton from a nucleus. Proton decay is shown from a normal spherically shaped nucleus and from a deformed, football- shaped nucleus. Researchers have found that the rates of proton radioactivity are different for the two types of nuclei because of their different shapes.

Alpha Decay: Nucleus emits a helium nucleus (called an Alpha Particle) and gets converted to another nucleus with atomic number lesser by 2 and atomic weight lesser by 4.
 

Beta Decay: Beta decay could be of two types; either through emission of an electron or positron (the antiparticle of electron). Electron emission causes an increase in the atomic number by 1, while positron emission causes a decrease in the atomic number by 1. In some cases, double beta decay may occur, involving the emission of two beta particles.
 

Gamma Decay: Gamma decay just changes the energy level of the nucleus.
 

Electron Capture: One of the rarest decay modes is electron capture. In this phenomenon, an electron is captured or absorbed by a proton rich nucleus. This leads to the conversion of a proton into a neutron in the nucleus, along with release of an electron neutrino. This leads to a decrease in atomic number (transmuting the element in the process), while leaving the atomic mass number unchanged.

A radioactive element may have more than one decay mode.

Polonium:

Polonium is a chemical element with the symbol Po and atomic number 84, discovered in 1898 by Marie and Pierre Curie. 

Symbol: Po

Electron configuration: [Xe] 6s2 4f14 5d10 6p4

 Atomic radius: 190 pm

Atomic number: 84

Discovered: 1898

Atomic mass: 209 u

Polonium poisoning:The maximum safe body burden of Po-210 is only seven picograms. A microgram of Po-210, which is no larger than a speck of dust, would certainly deliver a fatal dose of radiation.  

Polonium is only slowly excreted - it has a biological half life of around a month - and this ensures its alpha particles continue to wreak havoc once inside the body. One likely method of administration would be as a soluble salt (citrate or nitrate, for example) added to the victim's food or drink.Once ingested, polonium is rapidly distributed around the body, leaving a trail of reactive radicals in its wake as it steals electrons from any molecule it encounters. Low-level DNA damage from radiation can cause genetic changes that affect cell replication, whereas more severe damage may force the cell to self destruct by apoptosis.

The alleged mysteries:

The body of the former Palestinian leader Yasser Arafat is being exhumed on Tuesday today to test to see if he was the victim of Polonium-210 poisoning. The tests will attempt to establish the cause of his death in Paris in 2004.

Polonium was first discovered by Marie and Pierre Curie in 1898. It is a radioactive element that occurs naturally in the earth's crust.

According to scientists from the University of Chicago Polonium-210 is traditionally used to clear dust from camera lenses or photographic film.

It is poisonous if ingested and it's believe that the Russian dissident Alexander Litvinenko who died in November 2006 was the victim of Polonium-210 poisoning.
 *Note: all pictures thankfully shared from various sources..