1. The G-series is named because German scientists first synthesized them. G series agents are known as non-persistent, while the V series are persistent. The first nerve agent synthesised was GA (Tabun) in 1936. GB (Sarin) was discovered next in 1939, followed by GD (Soman) in 1944 and finally the more obscure GF (Cyclosarin) in 1949.
2. The V-series were developed in the 1950s. Workers at ICI in the UK were looking for new organophosphorous pesticides. In 1954, ICI put one of them on the market under the trade name Amiton. It was subsequently withdrawn, as it was too toxic for safe use. The toxicity did not go unnoticed and some of the more toxic materials had in fact been sent to the Chemical Defence Establishment at Porton Down for evaluation. After the evaluation was complete, several members of this class of compounds became a new group of nerve agents, the V agents (depending on the source, the V stands for Victory, Venomous, or Viscous). The best known of these is probably VX, with the Russian V-gas coming a close second (Amiton is largely forgotten as VG). This class of compounds is also sometimes known as Tammelin's esters, after Lars-Erik Tammelin of the Swedish Institute of Defense Research who first synthesised a number of the agents.
3. The Novichok  (Russian for "newcomer") agents are a series of organophosphorous compounds that were developed in the Soviet Union from the mid-1960s to the 1990s. The goal of this program was to develop and manufacture highly deadly chemical weapons that were unknown to the West. These new agents were designed to be undetectable using standard 1970s and 80s NATO chemical detection equipment; to defeat NATO chemical protective gear; to be safer to handle; and to circumvent the Chemical Weapons Convention list of controlled precursors, classes of chemical and physical form.

Cyclohexyl methylphosphonofluoridate  [Cyclosarin, GF] - C₇H₁₄FO₂P

A colorless liquid, odorless to fruity odour, possibly of peach. Cyclosarin is readily absorbed through skin, eyes, and respiratory tract with inhalation and dermal routes of exposure posing significant threats.Toxic manifestations of exposure to cyclosarin vapor or aerosols occur within seconds to minutes of inhalation, while signs and symptoms of percutaneous exposure to liquid cyclosarin may take a minute to hours.

Isopropyl methylphosphonofluoridate  [Sarin, GB] - C₄H₁₀FO₂P

In the pure form a colourless, odourless liquid. Exposure is lethal even at very low concentrations, where death can occur within one-to-ten minutes after direct inhalation of a lethal dose, due to suffocation from lung muscle paralysis, unless antidotes are quickly administered. People who absorb a non-lethal dose, but do not receive immediate medical treatment, may suffer permanent neurological damage.

O-butyl S-[2-(diethylamino)ethyl] methylphosphonothioate [Chinese VX, EA-6043] - C₁₁H₂₆NO₂PS

A structural isomer of VX. It is an organic thiophosphate that is an ester of S-[2-(diethylamino)ethyl] O hydrogen methylphosphonothioate. A toxic nerve agent developed by the Peoples' Republic of China. It has a role as a neurotoxin and an EC 3.1.1.7 (acetylcholinesterase) inhibitor. It is an organic thiophosphate and a tertiary amino compound.

O-Ethyl N,N-dimethyl phosphoramidocyanidate [Tabun, GA] - C₅H₁₁N₂O₂P

A clear, colourless to brownish, and tasteless liquid with a faint fruity odor. The symptoms of exposure include: nervousness/restlessness, miosis , rhinorrhea, excessive salivation, dyspnea, sweating, bradycardia, loss of consciousness, convulsions, flaccid paralysis, loss of bladder and bowel control, apnea and lung blisters. The exact symptoms of overexposure are similar to those created by all nerve agents. Tabun is toxic even in minute doses. The number and severity of symptoms which appear vary according to the amount of the agent absorbed and rate of entry of it into the body. Very small skin dosages sometimes cause local sweating and tremors accompanied with characteristically constricted pupils with few other effects. Tabun is about half as toxic as sarin by inhalation, but in very low concentrations it is more irritating to the eyes than sarin. The effects of tabun appear slowly when tabun is absorbed through the skin rather than inhaled. A victim may absorb a lethal dose quickly, although death may be delayed for one to two hours. A person's clothing can release the toxic chemical for up to 30 minutes after exposure. Inhaled lethal dosages kill in one to ten minutes, and liquid absorbed through the eyes kills almost as quickly. However, people who experience mild to moderate exposure to tabun can recover completely, if treated almost as soon as exposure occurs.

O-Ethyl S-2-diisopropylaminoethyl methyl phosphonothiolate [Methylphosphonothioic acid, VX] - C₁₁H₂₆NO₂PS 

A clear, amber-colored odorless, oily liquid. People exposed to a low or moderate dose of VX by inhalation, ingestion (swallowing), or skin absorption may experience some or all of the following symptoms within seconds to hours of exposure: abnormally low or high blood pressure, blurred vision, chest tightness, confusion, cough, diarrhea, drooling, excessive sweating, drowsiness, eye pain, headache, increased urination, nausea, vomiting, abdominal pain, tachypnea, rhinitis, bradycardia, tachycardia, miosis, lachrymation, weakness. Even a tiny drop of nerve agent on the skin can cause sweating and muscle twitching where the agent touched the skin.

Exposure to a large dose of VX by any route may result in these additional health effects: convulsions, loss of consciousness, paralysis, respiratory failure possibly leading to death.

O-(iso-Butyl) S-(2-diethylaminoethyl) methylphosphonothiolate [VR, Russian VX, VR is an isomer of VX] -  C₁₁H₂₆NO₂PS 

VR has similar lethal dose levels to VX. Acute exposure to a lethal dose of VR has been shown to cause cholinergic hyperfunction, incapacitation, seizures, convulsions, cardiorespiratory depression and death.

O-Pinacolyl methylphosphonofluoridate [Soman, GD] - C₇H₁₆FO₂P 

A volatile, corrosive, and colorless liquid with a faint odor like that of mothballs or rotten fruit. In the impure form it has a yellow to brown colour and has a strong odour described as similar to camphor.  It is both more lethal and more persistent than sarin or tabun, but less so than cyclosarin.

O,O-diethyl S-[2-(diethylamino)ethyl] phosphorothioate [VG, Amiton, Tetram] - C₁₀H₂₄NO₃PS 

VG has a toxicity of about 1/10 that of VX, i.e. similar to that of sarin.

O-cyclopentyl S-(2-diethylaminoethyl) methylphosphonothiolate [EA-3148, Substance 100A] - C₁₂H₂₆NO₂PS

Probably too unstable to be weaponise.

Propan-2-yl ethylphosphonofluoridate  [Ethyl sarin, E1209, GE] C₅H₁₂FO

Odourless and colourless to yellow-brown liquid. The effect of exposure to Ethyl sarin depends on the amount of the agent, route and duration of the exposure. The symptoms will appear within a few seconds after inhalation exposure to the vapour form and from a few minutes to 18 hours after exposure to the liquid form. Ethyl sarin may be absorbed quickly and easily. When dispersed as a vapour or aerosol, or absorbed on dust, it is readily absorbed through the respiratory tract and conjunctivae. Absorption is most rapid and complete through the respiratory tract. Aerosols and liquids are also absorbed through skin. Vapours may be absorbed through skin if at very high concentrations.  Liquid droplets or even vapor may persist in a victim's clothes after minutes to hours of exposure which may lead to cross-contamination of others.

S-[2-(Diethylamino)ethyl] O-ethyl methylphosphonothioate [Edemo, VM], C₉H₂₂NO₂PS

Similar lethal dose levels to VX (between 10 and 50 mg) and have similar symptoms and method of action to other nerve agents.