Valence Bond (VB) Theory Definition

Valence bond (VB) theory is a chemical bonding theory that explains the chemical bonding between two atoms. Like molecular orbital (MO) theory, it explains bonding using principles of quantum mechanics. According to valence bond theory, bonding is caused by the overlap of half-filled atomic orbitals. The two atoms share each others unpaired electron to form a filled orbital to form a hybrid orbital and bond together. Sigma and pi bonds are part of valence bond theory. Key Takeaways: Valence Bond (VB) Theory Valence bond theory or VB theory is a theory based on quantum mechanics that explains how chemical bonding works.In valence bond theory, the atomic orbitals of individual atoms are combined to form chemical bonds.The other major theory of chemical bonding is molecular orbital theory or MO theory. Valence bond theory is used to explain how covalent chemical bonds form between several molecules. Theory Valence bond theory predicts covalent bond formation between atoms when they have half-filled valence atomic orbitals, each containing a single unpaired electron. These atomic orbitals overlap, so electrons have the highest probability of being within the bond region. Both atoms then share the single unpaired electrons to form weakly coupled orbitals. The two atomic orbitals do not need to be the same as each other. For example, sigma and pi bonds may overlap. Sigma bonds form when the two shared electrons have orbitals that overlap head-to-head. In contrast, pi bonds form when the orbitals overlap but are parallel to each other. This diagram depicts a sigma bond between two atoms. The red area represents localized electron density. ZooFari  /  Creative Commons Attribution-Share Alike 3.0 Unported license Sigma bonds form between electrons of two s-orbitals because the orbital shape is spherical. Single bonds contain one sigma bond. Double bonds contain a sigma bond and a pi bond. Triple bonds contain a sigma bond and two pi bonds. When chemical bonds form between atoms, the atomic orbitals may be hybrids of sigma and pi bonds. The theory helps explain bond formation in cases where a Lewis structure cant describe real behavior. In this case, several valence bond structures may be used to describe a single Lewis stricture. History Valence bond theory draws from Lewis structures. G.N. Lewis proposed these structures in 1916, based on the idea that two shared bonding electrons formed chemical bonds. Quantum mechanics was applied to describe bonding properties in the Heitler-London theory of 1927. This theory described chemical bond formation between hydrogen atoms in the H2 molecule using Schrà ¶dingers wave equation to merge the wavefunctions of the two hydrogen atoms. In 1928, Linus Pauling combined Lewiss pair bonding idea with the Heitler-London theory to propose valence bond theory. Valence bond theory was developed to describe resonance and orbital hybridization. In 1931, Pauling published a paper on valence bond theory entitled, On the Nature of the Chemical Bond. The first computer programs used to describe chemical bonding used molecular orbital theory, but since the 1980s, principles of valence bond theory have become programmable. Today, the modern versions of these theories are competitive with each other in terms of accurately describing real behavior. Uses Valence bond theory can often explain how covalent bonds form. The diatomic fluorine molecule, F2, is an example. Fluorine atoms form single covalent bonds with each other. The F-F bond results from overlapping pz orbitals, which each contain a single unpaired electron. A similar situation occurs in hydrogen, H2, but the bond lengths and strength are different between H2 and F2 molecules. A covalent bond forms between hydrogen and fluorine in hydrofluoric acid, HF. This bond forms from the overlap of the hydrogen 1s orbital and the fluorine 2pz orbital, which each have an unpaired electron. In HF, both the hydrogen and fluorine atoms share these electrons in a covalent bond. Sources Cooper, David L.; Gerratt, Joseph; Raimondi, Mario (1986). The electronic structure of the benzene molecule. Nature. 323 (6090): 699. doi:10.1038/323699a0Messmer, Richard P.; Schultz, Peter A. (1987). The electronic structure of the benzene molecule. Nature. 329 (6139): 492. doi:10.1038/329492a0Murrell, J.N.; Kettle, S.F.A.; Tedder, J.M. (1985). The Chemical Bond (2nd ed.). John Wiley Sons. ISBN 0-471-90759-6.Pauling, Linus (1987). Electronic structure of the benzene molecule. Nature. 325 (6103): 396. doi:10.1038/325396d0Shaik, Sason S.; Phillipe C. Hiberty (2008). A Chemists Guide to Valence Bond Theory. New Jersey: Wiley-Interscience. ISBN 978-0-470-03735-5.

The Salem Witch Trials Essay - 1584 Words

The Salem Witch Trials Throughout our nation s history, Americans have survived times of struggle by remaining strong and brave despite their fears. Disease, natural disasters, and starvation are just a few of the trials our country has faced. While these are certainly dangerous, perhaps the most frightening of all is when you fear those closest to you. This is what happened during the horrific frenzy labeled as the Salem Witch Trials. Nobody truly knows why they occurred, although there are several plausible theories. It all originated in seventeenth century New England, in a tiny place called Salem Village (History.com). In 1629, a small group of people, known as Puritans, journeyed across the Atlantic Ocean to the New World, leaving†¦show more content†¦The fear of the Invisible World was so deeply rooted in the hearts of the Puritans that one of their laws was death to anyone making a pact with the Devil (Meltzer 70). Without doubt or question, the Puritans realized that God was warning them with signs across the land; earthquakes, hurricanes, war, smallpox, and even shooting stars were regarded with awe and fear (Schanzer 15). The Puritans were not the only people afraid, however; all of New England was plagued by problems. The New Englanders faced natural disasters, starvation, and sickness, but their biggest problems were the Indians. After the bloody King Philip s War of 1675-1676, the Native Americans still sought to drive out the white settlers, and continued destroying towns and killing innocent men. Most colonists believed that the Indians were pagan worshippers of the Devil, and Cotton Mather, a Boston minister, wrote, the Devil is engaged in this hellish design of bewitching and ruining our land† (Meltzer 73). The Wabonaki Indians in particular became the Puritans greatest enemy, and, they reasoned, the source of all problems and sin. The Wabonakis felt that the Puritans had intruded on their land, while the Puritans believed that the Wabonakis had no right to it. Fortunately, in 1681, the Wabonakis signed a truce with the white settlers, promising

Case Study †Bowel Cancer Free Essays

Bowel Cancer The bowel is a long tube that is made up of the small bowel, colon and rectum. The bowel absorbs nutrients from food and also processes waste products into faeces to be removed from the body. Bowel Cancer is cancer of the rectum or colon. We will write a custom essay sample on Case Study – Bowel Cancer or any similar topic only for you Order Now Bowel cancer develops from small raised growths called polyps which are found in the inner lining of the bowel. These polyps can either be non cancerous and harmless (benign) or they can be cancerous (malignant). All polyps should be removed to reduce the risk of these polyps becoming cancerous or spreading the disease further. Most polyps can be removed without surgery with a procedure called a colonoscopy. If these polyps are not removed, they can grow deeper into the bowel and spread into areas close to the area and later can spread to the liver or lungs. Causes Bowel cancer can be hereditary passed down from a before generation but mainly age and lifestyle factors also contribute to the development of bowel cancer. According to the Better Health Channel (BHC)(2011), There is some evidence that having a diet that consists of red meat and drinking alcohol can lead to the cause of bowel cancer. Bowel cancer is more common in people aged 50 years or older. In relation to â€Å"Lou† who is 75, eats red meat from the cattle from his farm and also drinks alcohol, his risk factors for bowel cancer was high. This inability to pass bowel movements showed that he had a very high chance of having bowel cancer. Symptoms * Blood or mucus in the faeces Weakness and paleness * Diarrhoea * Constipation * Finding your faeces are narrower than usual * Feeling that your bowel doesn’t empty completely Prevalence rates According to Bowel Cancer Australia (BCA)(2010), Bowel cancer is the responsible for the second biggest cancer related deaths after lung cancer with 14,234 people being diagnosed with bowel cancer each year and 4047 deaths occurring due to bowel cancer. The older you become the greater t he risk of developing bowel cancer becomes with Cancer Council Australia CCA)(2011), quoting that 1 in 12 Australians develop bowel cancer before the age of 85. Bowel cancer is the most curable cancer and if detected and removed early, the cure rate is 90%, however in most cases; bowel cancer is detected in its later stage and therefore has a 60% cure rate. Table: Age vs Number of cases. Obtained from Australian Institute of Health and Wellfare (2006). Socio-Ecological Model Socio-Ecological Model (SEM) is a framework that recognises the relationship that is present between an individual and its surrounding environment. This model looks at not only at an individual reducing risk and improving health but also looks at the outer environment. These include the public policy, the community, organisations, interpersonal and the individual themselves. People who are diagnosed with bowel cancer can suffer from psychological problems due to the trauma of going through the procedures when diagnosing the cancer (such as colonoscopy) or from during the procedure where the doctor has to perform surgery on the patient. Mainly psychological affects will come from the fear of death and can lead them to withdraw themselves from friends and family leading to the sufferer not being socially active and not having that connection that is needed to get through the mental trauma that can be associated when dealing with bowel cancer. In this case the SEM can be implemented as for a patient that is suffering from psychological problems as they would need good interpersonal relationships (friends and family) and organisational involvement (social institutions) to be there to help the patient deal with their illness as best as possible. As in the case of â€Å"Lou† from the case study, he is moving 50 km away from his home, friends and family and therefore could lead him to feel that he can’t connect with anyone and lead to emotional and social consequences which include depression. Social Services and Programs There are many support groups and services that are available to help a cancer patient when needed. If these are utilised, it can be beneficial in dealing with the emotional and social impacts that come with the disease. These include: * Homecare: This I when a social worker or nurse provides a cancer patient with their basic needs e. g. running errands, preparing meals, medication delivery and can have regular visits from physical therapists. This is a good asset as patients often feel more comfortable in their own home where they can be close to friends and family. This puts a great demand on other people like social workers, nurses and physical therapists to play a major role for home care to be achieved. This is also applied from the (SEM). Social workers: Can either be seen at home from home care or cancer patients can go see social workers. Social workers can offer counselling, counselling for the future, access to support groups and referrals to specialists. This Is good as it can help a cancer patient during and after they have cancer. * Cancer rehabilitation programs: The Cancer Nutrition Rehabilitation Program gives cancer patients information about diet, physical activity, treatment and ot her needs to successfully become rehabilitated. The social worker helps the patient obtain the needs necessary and give them general direction on how to become and maintain a healthy state after cancer. Conclusion Bowel cancer can be successfully treated and cured if early detection is made. This early detection will heighten the chances of survival then if it is found at a later stage. Regular checkups for people over 50 years of age are necessary to ensure that this early detection occurs. While an individual is responsible to obtain a healthy lifestyle, other factors need to be taken into account as outlined from the SEM. If individuals and the surrounding environment are linked together as one then becoming and staying healthy can be achieved. Reference List. 1. Polglase A (2010) Let’s beat bowel cancer. Australian Pharmacist. Vol 29, issue 5, 414-416. Available from, http://ea3se7mz8x. search. serialssolutions. com/? ctx_ver=Z39. 88-2004;ctx_enc=info%3Aofi%2Fenc%3AUTF-8;rfr_id=info:sid/summon. serialssolutions. com;rft_val_fmt=info:ofi/fmt:kev:mtx:journal;rft. genre=article;rft. atitle=Let%27s+Beat+Bowel+Cancer;rft. jtitle=Australian+P How to cite Case Study – Bowel Cancer, Free Case study samples

HIM Careers - Health Information

Question: Describe about AHIMA.org and search articles regarding AHIMA's Envision of the Future of HIM? Answer: Introduction AHIMA also known as The American Health Information Management Association provides professional and academic support to its community members by offering them professional accreditation services, educational opportunities and professional journals to aid in the process of Health Information Management (HIM). The organizations major strategic element is to provide all significant medical information from electronic health information to paper infrastructure. AHIMA has always been on the move analyzing its strategic elements of innovation and technological advancements (Ahima.org, 2016). AHIMA till date has represented more that 71,000 management professionals in health all over USA and the world. AHIMA has always been keen and committed towards advocating and promoting various researches of the highest quality, effective standards and best practices in health information. It is also actively contributing towards the advancements and developments of health information professional all around the world. Future Envision AHIMAs Building a Work Force for the Future educational perspectives in Information management and Health Informatics targets the development of the health information management profession by bringing efficient changes in the education system for producing future work force. According to Rebecca B. Reynolds, EdD, RHIA, FAHIMA and the associate professor of health informatics and information management the basic need for continuously looking at the competencies and learning outcomes of the student is to ensure that HIM workforce is developing on appropriate levels to meet the most critical industrial needs of the healthcare industry (Ahima.org, 2016). According to a survey conducted by a researcher it was analyzed that HIM competency is the most dominant education along with the most years of experience in the field. Educational programs related to HIM are the most significant aspect in the current environment in which most professionals will work in the future. As per the competenci es of the Global Health Informatics Education US the global curriculum is the most flexible framework which operates across various cultures and develops the competencies related to health management and health environment along with various abilities and skills. The program will significantly need adaptation to the local environment for being most efficient. It can be used as a core competency which will enable to provide the basic foundation for local adaption in every environment. Discussion Conclusion AHIMA has been quite influential in advocating quality research and practices that enables the professionals to be skilled in the field of HIM (Library.ahima.org, 2016). HIM has been the most virtual and future prospect educational field framed out by AHIMA. The organization has taken significant steps and ideas to provide the knowledge infrastructure along with framing envision for the future. The future vision of HIM is to provide quality healthcare, research and practices via quality information with the specific use of technological advancements. The vision of HIM is to conceptualize on the basic needs of the healthcare field by formulating various skilled and able professionals that adapt to the local environment and provide the most efficient service ("Long Term Care Facts. Washington, American Health Care Association", 1978). HIM values the publics right to confidential and accurate personal health information and respond to the policy strategies, research and information that keeps HIM to attain the goals and objectives with the vision of Better Health Information for All. References Ahima.org,. (2016).HIM Careers - Health Information 101. Retrieved 1 March 2016, from https://www.ahima.org/careers/healthinfo Ahima.org,. (2016).HIM Careers - Planning your education. Retrieved 1 March 2016, from https://www.ahima.org/careers/plan Library.ahima.org,. (2016).Search Results. Retrieved 1 March 2016, from https://library.ahima.org/xpedio/idcplg?IdcService=GET_SEARCH_RESULTSQueryText=xPublishSite%3Csubstring%3E%60BoK%60%3Cand%3ExSource%3Ccontains%3E%60AHIMA+Journal%60adhocquery=1urlTemplate=/xpedio/groups/public/documents/web_assets/queryresults.hcspResultCount=25SortField=xPubDateSortOrder=Desc Long Term Care Facts. Washington, American Health Care Association. (1978).Health Care Management Review,3(1), 88. https://dx.doi.org/10.1097/00004010-197824000-00013