The Aufbau Principleâ€Definition, Rules and Exceptions

The Aufbau Principle- Definition, Rules and Exceptions The Aufbau principle, simply put, means electrons are added to orbitals as protons are added to an atom. The term comes from the German word aufbau, which means built up or construction. Lower electron orbitals fill before higher orbitals do, building up the electron shell. The end result is that the atom, ion, or molecule forms the most stable electron configuration. The Aufbau principle outlines the rules used to determine how electrons organize into shells and subshells around the atomic nucleus. Electrons go into the subshell having the lowest possible energy.An orbital can hold at most 2 electrons obeying the Pauli exclusion principle.Electrons obey Hunds rule, which states that electrons spread out before they pair up if there are two or more energetically equivalent orbitals (e.g., p, d). Aufbau Principle Exceptions Like most rules, there are exceptions.  Half-filled and completely filled d and f subshells add stability to atoms, so the d and f block elements dont always follow the principle. For example, the predicted Aufbau configuration for Cr is 4s23d4, but the observed configuration is actually 4s13d5. This actually reduces electron-electron repulsion in the atom, since each electron has its own seat in the subshell. Aufbau Rule Definition A related term is the Aufbau Rule, which states that the filling of different electron subshells is by order of increasing energy following the (n 1) rule. The nuclear shell model is a similar model that predicts the configuration of protons and neutrons in an atomic nucleus.

AP Exams vs SAT Subject Tests Whats More Important

AP Exams vs SAT Subject Tests What's More Important SAT / ACT Prep Online Guides and Tips Many high-achieving students end up taking both SAT Subject Tests and AP Tests during their time in high school. SAT Subject Tests are required for admission to mostcompetitive colleges, and AP Tests and coursework are encouraged. Is one more important than the other? In this article, I’ll give details on how these two types of tests compare to each another and whether it's a good idea to take AP Tests and SAT Subject Tests in the same topic areas. What's the Difference Between AP Tests and SAT Subject Tests? SAT Subject Tests are hour-long multiple-choice exams that are scored on a scale of 200 to 800.AP Tests consist of multiple choice and essay sections, last for several hours, and are scored on a scale of 1-5. Many more students take AP tests every year than SAT Subject Tests (2.3 million versus about 500,000). This is becauseAP Tests are tied directly to the corresponding Advanced Placement classes. In recent years, the AP program has spread to more and more high schools across the country. To get college credit for these classes, students must pass the tests. SAT Subject Tests are less popular because students only take them for certain selective colleges that ask for them in the application process. The most selective schools usually require or recommend two or three subject tests. These tests are not directly tied to specific classes, so students typically have more freedom in deciding which ones they want to take. SAT Subject Test scores can showcase your unique interests and talents on your college application. SAT Subject Tests are rarer than AP Tests. This red panda is also rare, but it's much cuter than anything the College Board will ever create. What Is the Purpose of an AP Test Compared to That of an SAT Subject Test? AP Tests measure a student’s mastery of college-level subject matterthrough questions that touch on the main points of a year-long AP curriculum.Your AP Test scores validate the hard work you did in class and confirm that you learned the material. The dean of admissions at Harvard says, "We have found that the best predictors [of grades] at Harvard are Advanced Placement tests and International Baccalaureate Exams, closely followed by the College Board subject tests."Students who do well on AP Tests are likely to be successful in college classes, so selective schools are interested in them for their predictive value. AP Test scores alsohelp admissions officers decide whether your grades are an accurate reflection of your academic ability. If you got a 1 on the test but an A in the class, the class was probably way too easy. If you got a 5 on the test but a B- in the class, the class was probably very challenging. This will affect the judgments that admissions officers make about your potential. Your AP scores also make a difference in whether or not you earn college credit for the work you did in your AP class.At most schools, an AP score of 4 or 5 will either lead to college credit or allow you to place out of introductory college courses. SAT Subject Tests are slightly different because they measure students’ readiness for college-level work. SAT Subject Tests are sometimes used to place students out of courses in college, but you can’t earn college credits for doing well on them. They're also less relevant for predicting college grades, although they still have some value. Since SAT Subject Tests don't correspond with specific classes on your transcript, they can be used to emphasize your abilities in the subjects that are most relevant to what you plan on studying in college. Colleges view subject tests as assessments of how much you learned in high school and where your academic strengths lie. High scores on AP Tests might allow you to ascend the college escalator more quickly. Are AP Tests Harder Than SAT Subject Tests? Most students find the material on AP Tests to be more difficult than the material on SAT Subject Tests because it's intended for students who are working at a college level. AP Tests also require more stamina.As a rule, essays are almost always harder than multiple-choice questions because you have to come up with an answer entirely on your own. Even within the multiple choice sections, AP Tests demand a deeper understanding of the material than SAT Subject Tests.They also require students to possess more in-depth knowledge and analytical abilities when it comes to interpreting primary source materials. Still, it is technically easier to get a 5 on an AP Test than an 800 on an SAT Subject Test. On most AP Tests, you can still earn a 5 if you get a fair amount of questions wrong, whereas there’s almost no room for error on subject tests if you want a perfect score.A student who gets 70% of questions correct and a student who gets 100% of questions correct may both end up with 5s on an AP test depending on how strong the curve is. However, this is deceptive, since the actual content and test format for AP Tests is significantly more difficult.A student who earns a high score like a 700 on a subject test might not get a 5 on an AP Test due to the greater complexity.I'll do a comparison with real questions to show you how the two tests differ. Come with me on this journey down two divergent paths that wind through the strange wasteland of Collegeboardia. Here’s a sample multiple-choice question from the US History SAT Subject Test: "If the Creator had separated Texas from the Union by mountain barriers, the Alps or the Andes, there might be plausible objections; but He has planed down the whole [Mississippi] Valley including Texas, and united every atom of the soil and every drop of the water of the mighty whole. He has linked their rivers with the great Mississippi, and marked and united the whole for the dominion of one government, the residence of one people." This quotation from the 1840's can be viewed as an expression of: A. The New NationalismB. popular sovereigntyC. Manifest DestinyD. the Good Neighbor PolicyE. the frontier thesis (the answer is C) And here’s a sample multiple-choice question from the AP US History Test (multiple choice questions refer to excerpts from primary sources): Excerpt: â€Å"We conclude that in the field of public education the doctrine of ‘separate but equal’ has no place. Separate educational facilities are inherently unequal.† -Chief Justice Earl Warren, writing the unanimous opinion of the United States Supreme Court in Brown v. Board of Education of Topeka, 1954 Which of the following was the most immediate result of the decision excerpted? A. Radicals critiqued government actions as doing too little to transform the racial status quo. B. Education advocates raised awareness of the effect of poverty on students’ opportunities. C. Civil rights activists became increasingly divided over tactical and philosophical issues. D. Segregationists in southern states temporarily closed many public schools in an effort to resist the decision. (the answer is D) Notice the differences between these two questions.The SAT Subject Test question is much more straightforward.It requires basic knowledge of terminology related to US History.Most students who took any standard class in US History would probably answer it correctly. The AP Test question, on the other hand, is more nuanced.It asks for the â€Å"most immediate† result of the Supreme Court decision.All of the answers are true to some degree, but only D reflects the â€Å"most immediate† initial response.This is tricky, and it requires students to think more carefully about the question.It expects a certain degree of advanced knowledge of larger trends related to racial tension in US History and when and how the responses of different groups to legislative changes played out. You can also see this difference between the two tests magnified in the open response section of the AP Test. Here’s an example of an AP open response question: Using your knowledge of United States history, answer parts a and b. a) Briefly explain why ONE of the following periods best represents the beginning of a democracy in the United States. Provide at least ONE piece of evidence from the period to support your explanation. Rise of political parties in the 1790s Development of voluntary organizations to promote social reforms between the 1820s and the 1840s Emergence of the Democrats and the Whigs as political parties in the 1830s b) Briefly explain why ONE of the other options is not as persuasive as the one you chose. This question requires students to formulate a coherent definition of American democracy, make a decision about which time period best exemplifies its roots (while backing up their point with historical knowledge), and refute a counterargument.This is college-level analytical thinking.You won’t encounter questions like this on an SAT Subject Test. Choose your responses carefully. Uncle Sam is watching. Should You Take SAT Subject Tests and AP Tests in the Same Subjects? Is it OK to take SAT Subject Tests and AP Tests in the same subject? Yes, colleges won't think you're being lazy if you have overlap in the two exam types. The key factor when deciding which SAT Subject Tests to take isn't how similar or different they are to your AP Tests, it's if those SAT Subject Tests fit the subject test requirements of the schools you're applying to. If the colleges where you’re applying simply request that you take two or three unspecified SAT Subject Tests, it makes a lot of sense to take the tests that correspond with your APs. Since SAT Subject Tests are less challenging than AP Tests, you will already be prepared and may not have to do any extra studying.AP Tests are typically held in May, and you can take SAT Subject Tests in June. Certain college programs do require you to take specific subject tests to be eligible for admission.This is often the case at engineering schools that want to ensure students are well-versed in math and the hard sciences.For example, the California Institute of Technology requires prospective students to take the Math 2 subject test and one of the subject tests in Biology, Physics, or Chemistry.Math 2 is the most commonly required SAT Subject Test. If you aren’t taking an AP Test in the same subject area as the SAT Subject Test you want or need to take, you should plan to take the subject test at the end of your most relevant high school class.For Math 2, this will most likely be at the end of your junior year after you’ve taken classes in algebra, geometry, trigonometry, and precalculus.In general, it’s always a good idea to take an SAT Subject Test right after you finish a class in the subject.That way, you can just do a quick review and avoid having to refresh your memory on material you learned a while ago. You, radiating confidence during your SAT Subject Tests. Conclusion AP Tests and SAT Subject Tests differ in many ways, although they both can have an impact on your chances of admission at competitive colleges. SAT Subject Tests are only an hour long, and they are comprised entirely of multiple-choice questions. AP Tests, on the other hand, can last for over three hours and always include both multiple-choice and essay questions. AP Tests are associated with specific AP classes, and their content tends to be more challenging than that of SAT Subject Tests. AP Tests ask students to demonstrate college-level analytical skills while SAT Subject Tests require more basic knowledge of high school curriculum. Your scores on AP Tests may also earn you college credit or allow you to place out of introductory college classes if they are high enough. SAT Subject Tests are only occasionally used for placement purposes. Both types of tests may be important for you in the admissions process, so make sure that you prepare accordingly! What's Next? Curious about AP? Learn how you can register for Advanced Placement classes and tests. If you're looking to delve deeper into variations in difficulty on AP tests, read this article on the hardest AP tests that you can take. If you're planning on taking SAT Subject Tests, take a look at this article to get a better sense of your ideal score range. Need a little extra help prepping for your Subject Tests? We have the industry's leading SAT Subject Test prep programs (for all non-language Subject Tests). Built by Harvard grads and SAT Subject Test full or 99th %ile scorers, the program learns your strengths and weaknesses through advanced statistics, then customizes your prep program to you so that you get the most effective prep possible. Learn more about our Subject Test products below: