In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to other atoms were fully ionic. It describes the degree of oxidation of an atom in a chemical compound. Conceptually, the oxidation state may be positive, negative or zero. Beside nearly-pure ionic bonding, many covalent bonds exhibit a strong ionicity, making oxidation state a useful predictor of charge.
The 400 metres, or 400-meter dash, is a sprint event in track and field competitions. It has been featured in the athletics programme at the Summer Olympics since 1896 for men and since 1964 for women. On a standard outdoor running track, it is one lap around the track. Runners start in staggered positions and race in separate lanes for the entire course. In many countries, athletes previously competed in the 440-yard dash (402.336 m)—which is a quarter of a mile and was referred to as the "quarter-mile"—instead of the 400 m (437.445 yards), though this distance is now obsolete.
The women's 400 metres at the 2004 Summer Olympics as part of the athletics program were held at the Athens Olympic Stadium from August 21 to 24. The winning margin was 0.14 seconds.
The women's 4 × 400 metres relay at the 2004 Summer Olympics as part of the athletics program was held at the Athens Olympic Stadium from August 27 to 28. The sixteen teams competed in a two-heat qualifying round in which the first three teams from each heat, together with the next two fastest teams, were given a place in the final race.
Chad competed at the 2004 Summer Olympics in Athens, Greece, from 13 to 29 August 2004. The country's participation at Athens marked its tenth appearance in the Summer Olympics since its debut at the 1964 Summer Games in Tokyo, Japan. The delegation included two track and field athletes; Djikoloum Mobele in the men's 100 metres and Kaltouma Nadjina in the women's 400 metres. Both athletes participated at the Games through wild card places since they did not meet the required standards to qualify. Nadjina progressed past the first round of her competition, but was eliminated in the semi-finals.
Sanya Richards-Ross is a retired Jamaican-born American track and field athlete who competed internationally for the United States in the 400-meter sprint. Her notable accolades in this event include being the 2012 Olympic champion, 2009 world champion, 2008 Olympic bronze medalist, and 2005 world silver medalist. With her victory in 2012, she became the second American woman to win the 400 meters at the Olympic Games and the first American woman to earn multiple global 400-meter titles. At this distance, Richards-Ross is also a six-time U.S. national champion.
The 4 × 400 metre relay at the 2005 World Championships in Athletics was held at the Helsinki Olympic Stadium on August 13 and August 14.
Christine Ijeoma Ohuruogu, MBE is a British former track and field athlete who specialised in the 400 metres, the event for which she is an Olympic, World and Commonwealth champion. The Olympic champion in 2008, and silver medalist in 2012, she is a double World Champion, having won the 400 m at the 2007 and 2013 World Championships. She has also won six World championship medals in the women's 4 × 400 m relay as part of the Great Britain and Northern Ireland team and bronze Olympic medals in the women's 4 × 400 m relay at the 2008 Beijing Games and the 2016 Rio Games, her final Olympics. Ohuruogu shares with Merlene Ottey and Usain Bolt the record for medalling in most successive global championships – 9 – between the 2005 World Championships in Athletics and the 2016 Summer Olympics.
The 4 × 100 metres relay at the 1997 World Championships in Athletics was held at the Olympic Stadium on August 8 and August 9.
Sudan sent a delegation to compete at the 2008 Summer Olympics in Beijing, China. Nine competitors, all from the Darfur region and northern Sudan, represented Sudan at the Beijing games.
Guyana sent a team to compete at the 2008 Summer Olympics in Beijing, China. Four representatives of Guyana qualified to take part in the Beijing Games–Adam Harris, Marian Burnett, and Aliann Pompey in track, and Niall Roberts in swimming–and Pompey advanced past the first round in her event, progressing to semifinals. Meanwhile, Alika Morgan and Geron Williams (cycling) took part in the Games' Youth Olympics camp, held in Beijing at the same time as the Olympics. Along with coaches and administrative members, Guyana sent a total of ten people to Beijing. The appearance of Guyana's delegation in Beijing marked the fifteenth Guyanese Olympic delegation to appear at an Olympic games, which started with their participation as British Guiana in the 1948 Summer Olympics. There were no medalists from Guyana at the Beijing Olympics. Roberts was Guyana's flagbearer at the ceremonies in Beijing.
Jamaica sent a delegation to compete at the 2008 Summer Olympics, held in Beijing, China from August 8 to August 24, 2008. This was, by far, Jamaica's best showing at the Summer Olympics; it was the nation's largest delegation yet, and its athletes nearly doubled its total gold medal count in addition to breaking the nation's record for number of medals earned in a single games. Jamaica's appearance at Beijing was its fifteenth consecutive appearance and appearance as an independent nation, although it had previously participated in four other games as a British colony and as part of the West Indies Federation. In the 29 events that included Jamaican athletes, there were 26 cases in which a Jamaican athlete or relay progressed to a final round. Usain Bolt won three of Jamaica's six gold medals at Beijing, breaking an Olympic and world record in all three of the events in which he participated. Shelly-Ann Fraser led an unprecedented Jamaican sweep of the medals in the Women's 100 m. Female sprinter Veronica Campbell-Brown carried Jamaica's flag at the ceremonies.
Natasha Monique Hastings is an American 400 meter track and field sprinter.
The women's 400 metres competition at the 2012 Summer Olympics took place between 3–5 August at the Olympic Stadium.
The women's 4 × 400 metres relay competition at the 2012 Summer Olympics in London, United Kingdom was held at the Olympic Stadium on 10–11 August. 2012
Difluorophosphate or difluorodioxophosphate or phosphorodifluoridate is an anion with formula PO2F−2. It has a single negative charge and resembles perchlorate and monofluorosulfonate in shape and compounds. These ions are isoelectronic, along with tetrafluoroaluminate, phosphate, orthosilicate, and sulfate. It forms a series of compounds. The ion is toxic to mammals as it causes blockage to iodine uptake in the thyroid. However it is degraded in the body over several hours.
