Selenium Tetrabromide

What is Selenium Tetrabromide?

Selenium Tetrabromide is a chemical compound with a molecular formula of (Br4)Se or SeBr4. It has a molecular weight of 398.587 grams/mole. It has is a chemically neutral charge with a 2D see-saw structure. The particles in the molecule are held together by covalent bonds. It is similar to selenium tetrafluoride and selenium tetrachloride in it's properties. The lewis diagram is above this paragraph. It was established before 1969 that Selenium Tetrabromide existed in a solid state. It appears as a powder and decomposes in water. The melting point is between 70-80 degrees Celsius. It is usually marked as a "dangerous" substance to come in contact with.

How is Selenium Tetrabromide formed?

Selenium Tetrabromide is formed through this reaction: SE + 2(Br2) = SeBr4

The crystal structure for this substance is below this paragraph. Thank you for reading this article!


Isotope Notation

Answer: Isotope Notation is a written form of an element which reveals not only its identity but also how many protons, neutrons and electrons it contains. This notation is very useful when you are trying to compare different "isotopes" of an element.

Isotopes are versions of elements which differ in the number of neutrons which they contain. Each version of the atom contain's the same number protons, and if the atom is electrically neutral, the same number of electron. The number of neutrons determines the isotope/mass number of the atom. Many elements have only a certain number of isotopes. Different isotopes vary in how stable they are chemically. For example, hydrogen has three different isotopes, with two being stable and one being unstable. Tritium, shown below, is the unstable isotope of hydrogen which decays.

Elements vary in how many different isotopes they have and the stability of each. For example, technetium has over 50 recorded isotopes with none of them being stable. This is quite different from hydrogen which does have stable isotopes. If you wanted to specify a specific atom of technetium you would also need to specify which of the 50 different types you were speaking of. This is why isotope notation is handy.

The graphic above displays the generic writing of an isotope. The element symbol is displayed to the right in a large font. Two different numbers are displayed to the left of the symbol in smaller font. The bottom number is the atomic number, or the number of protons in the atom. The top number is the mass number, which is the number of protons and neutrons combined. If you have two of the variables in this format, you can derive the third through simple calculations. Here is hydrogen's unstable isotope, tritium, written in isotope notation.
If you ever see this formatting, then you will now know what it means and how to interpret it.


The Law of Definite Proportions vs. The Law of Multiple Proportions

The Law of Definite Proportions (or Proust's Law) states that in a single chemical compound (such as H2O or CO) the ratio of it's component elements is a fixed whole number ratio. For example, in water (H2O) the ratio of hydrogen to oxygen is 2:1 (sometimes written 2/1). In Carbon monoxide (CO) the ratio of carbon to oxygen is 1:1 (or 1/1). Always remember that the law of definite proportions concerns the ratio of elements in a single compound. Here is the example of water visualized.

Law of Definite Proportions Example

This also applies if you use multiples of your original ratio. For example, you could double water's 2:1 hydrogen to carbon ratio. This result's in a 4:2 ratio with two water molecules produced as the end result. This is visualized below.

Law of Definite Proportions Second Example w/ Water

The Law of multiple proportions applies when two or more elements/compounds have multiple ways of combining into different compounds. This is different from the law of definite proportions where we looked at the ratio of elements in a single product, here we are looking at multiple products, as the name of the law implies. When you have a fixed amount of one element (such as carbon (C) or Nitrogen (N)) and you combine it with differing amounts of another element (such as oxygen (O)) the differing amounts of differing amounts of variable element can be expressed as a ratio of whole numbers. For example, the combination of carbon + oxygen forms two simple compounds which illustrate this point. The first is carbon monoxide (CO) and the second is carbon dioxide (CO2). If you start with a fixed 100 grams of carbon and combine it with 133 grams of oxygen, CO will be formed. If on the other hand you combine it with 266 grams of oxygen, CO2 is formed. The ratio of the different amounts of oxygen (266/133) simplifies to a whole number ratio of 2/1. This is the effect which the law of multiple proportions highlights. Another example using nitrogen monoxide and dioxide is illustrated in the example below.

Law of Multiple Proportions Example
  As we can see the ratio of the different oxygen levels (2.286/1.143) is a simple whole number ratio of 2:1 as the law of multiple proportions would have told us.

Thank you for reading! Hopefully you understand the difference between the law of definite proportions and the law of multiple proportions!


Building Your Project Idea on Scratch ↪ One Block at a Time

Creating larger projects is one of the main parts of Scratch. This does not always mean it is always easy, though. Huge projects can take hours, days, weeks, months, or even years! In this guide, we have broken down the steps of a project creating into three main parts; planning, creating, and sharing - each section with its own unique set of steps. If you have something to add to this guide, or just have a question, please leave a comment.

Planning is arguably the most important step of creating a project. You cannot just dive head first into your project, or it will end up unorganized and probably will not be as successful.

1.) Time. Approximate how long it will take you to complete the intended project. This will help keep you on track and it will help you set a release date! This is very important when it comes time to market and brand your project in the wider community. Many projects are released every second to the world, and you need to prepare in advance to make sure that your project stands out! You will also need to think of how much time you have, and how much time the project you want to create will take. If you do not have enough time, maybe this is not the project for you, or you should consider scaling back the size your project.

2.) Category Choice. You get to decide what type of project you would like to create. This will be important as it dictates what you are programming. You are not limited to any one category, such as games, animation, and art, but could do a combination of certain categories. This studio features many good examples of multiple categories mixed together. You can learn more about different popular project types on the wiki page. If none of these project categories work for you, or you would like to be inventive, you could try creating your own unique category!

3.) Research. Gain insight into how other projects in this category type are created. Draw inspiration from many sources, as you may find ways to improve the quality of your own project. See how others stylistically organized their projects, and you will personally be able to decide what styles you want to avoid, and what styles you want to highlight in your project. Drawing ideas and combining them in new ways is not copying, it is invention! Scratch is a community which builds on one another. If someone has already created a foundation for your idea, build off of it by remixing their project! Make sure though to always give credit to sources which you used!

Now for the fun part! It is time to start creating your project.

1.) Background. Choose what canvas you are going to set your project on. If you are making a painting app, then maybe a simple whiteboard is the best option, but if you are doing a complicated platformer, you are probably going to want a different backdrop for each level. The background will help dictate the tone which the project conveys. To quote the Google Dictionary, "tone" is “the general character or attitude of a place, piece of writing, situation, etc.” in this context. Backgrounds can be found in the backdrop library built into the project editor, or you can draw your own.

2.) Sprites. This is where you ask yourself, what types of sprites do I need? What function will my project serve? How will I program this so that it is as effective and efficient as possible? You should always have a general outline for what sprites you are going to need, if your project requires more, you can always add on at a later point in time. The sprites should help convey the context of the tone and should give the character life. If need you ever need help finding high-quality sprites, you can check out this studio called The Media Library.

3.) Programming. Programming is at the heart of your project! Any game can be changed hugely by how you program it, so make sure to do it just the way you want it! Also, don't be afraid to use other's scripts! Just make sure you give credit. Try to make it as efficient as possible, but if you don't know, remember that there are always friendly people in the Help with Scripts forum that can help!

4.) Comments. Leave comments behind in your project, so someone can exactly trace where/how you created a certain piece. Explaining your thought process in the moment is a great way to help yourself and others gain insight. By explaining to yourself how you created this project, you will be able to easily fabricate a better idea for your next project. Writing up these comments, however long or short, may give others the spark of creativity which they need to draw from new sources throughout their own “research phase”.

5.) Although it sounds simple, music can be one of the most important parts of projects and is often very overlooked. Music can help the background to dictate the tone, or it can just keep the viewer of the project interested. You can not just pick any music though, it has to fit with the theme of your project. If your project is a fun platformer, you could have some fast paced happy music. If you are creating an uplifting animation, you will want to find music that has the same theme.

This step does sound simple, but it can sometimes be a little challenging to make sure you do it right.

1.) Writing the Instructions and the Notes & Credits. Make sure to clearly explain all commands and parts of your project, if they are not included in an in-project tutorial. In your instructions, be sure to state what category your project belongs to, and what function it serves. If experienced users run the project and experience a glitch, they will be able to examine your text and help you fix the code so that it does carry out your intended function. In the notes, make sure to credit where you may have drawn earlier inspiration from. For copyright purposes, it is very important that you credit any music, art, images, and scripts from other users which you may have used. At the bottom, insert some tags with the categories that your project falls under. This will help improve your search rankings!

2.) Advertising. Use the Show+Tell forum and studios to introduce your project to the scratch community. Speak with scratchers about your project in advance, and get them excited for its release! If you can get a large enough love-spike, you could achieve high rankings in the “explore” category or even appear on the front page! Remember to not make projects simply to become “famous”. Although it is nice to be on the front page, your projects are good no matter how popular they are. Always be kind, if someone does not want to hear about it, then respect their decision. Try not to be too pushy while advertising. If you want to get your project curated, you can check out thenextcurator, to see a list of the upcoming FPCs who might be able to curate your project.

3.) Thumbnail. A good thumbnail will attract many viewers. The thumbnail should build up excitement for the project and should convey the tone at the same time. Try not to make your thumbnails look like clickbait or promising dubious claims. It should be honest and attractive and appeal to a large range of Scratchers. If you do not know how to create a thumbnail, then make sure to check out this tutorial! We would not recommend using an animated thumbnail since your project will never be eligible for the front page!

This guide was written by makethebrainhappy, ZLGames, jromagnoli and BrickWildcat. It was edited by pianogirl84, -Lite- and Drunken_Sailor. The amazing banner is by jromagnoli. The first graphic was made by BrownieBatter987 the second graphic was made by jromagnoli.