What does the number 40 in the name potassium-40 represent?

Questions

Whаt dоes the number 40 in the nаme pоtаssium-40 represent?

The fоllоwing is аn unbаlаnced chemical equatiоn:  __P4O10 + __H2O → __H3PO4 {"version":"1.1","math":"__P4O10 + __H2O → __H3PO4 "} Enter the correct coefficients for each reagent. 

Overview A cоmmоn culturаl expectаtiоn is thаt our college education ought to prepare us for our current or future careers. People are, by comparison, far less demanding that their education ought to go beyond workforce preparation and help improve their overall quality of life. For this proctored term paper assignment you will explain how the humanities can enhance your quality of life beyond mere workforce preparation. You will have 2.5 hours to write a response of at least 1,200 words.  Permitted Materials You may bring two handwritten notecards (front and back) with key ideas, quotes (with page numbers or timestamp), and an outline. No other notes, books, devices, or course materials are permitted. Your computer will be locked during the proctored session — you may not open other tabs, applications, or digital documents. The only aid you may use is your two notecards. Instructions Your core values (1 paragraph): Briefly explain what is intrinsically valuable to you. In other words, what do you care about for its own sake? What gives your life purpose? What are the humanities? (1-2 paragraphs): Drawing on knowledge gained in this course, explain what the humanities are and how your understanding has changed, if at all. Refer to at least one assigned text (lecture, video, or reading). How can the humanities help you live a good life (2-3 paragraphs): Present a reasoned and example-rich answer to the question, "How can/will the humanities help me live a good and meaningful life?" Refer to at least two assigned texts (lectures, videos, or readings) in this section. Requirements Course materials: Refer to at least three total assigned texts (lectures, videos, or readings) in your complete response. In-text citations referencing the author/title and page number or timestamp must be included. For example: (Epicurus 12) or (School of Life 3:30). Personal voice: Ground your claims in your own observations and/or creative thinking. Use first person ("I think," "I felt," "In my experience...").  Detailed examples: Support general claims with specific, concrete real or imagined examples. Do not simply state — demonstrate, show.* Reasoning: Explain the chain of thought that leads to each major claim/conclusion. Do not simply assert; walk the reader through your reasoned thought process. What you do not need: A formal Works Cited page, a structured introduction/conclusion, or MLA formatting beyond the in-text citations described above. Focus only on authoring substantive responses to each part of the prompt.  *For example, a general statement such as "Humanistic fields of study such as philosophy can help me think about what matters most to me" must be accompanied with specific supporting detail that demonstrates the point being made: "For example, a student of the humanities who has taken their exploration of philosophical reflection seriously is better equipped to think about whether or not the pay increase of a work promotion is worth sacrificing time with my daughter after school and coaching her soccer team."