chbare Posted October 21, 2009 Author Share Posted October 21, 2009 Unfortunately not. Most of what I am doing right now revolves around finding limiting reactants, reaction rates, calculating theoretical yield and percentage yield, thermodynamics, gas laws, and entropy/enthalpy calculations. However, many of these concepts require conversion of moles to grams and visa versa to plug the proper values into the formulas or dimensional analysis. So, it got me thinking about a common medication we often administer without fully appreciating what the numbers on the bag mean. Take care, chbare. Link to comment Share on other sites More sharing options...
armymedic571 Posted October 22, 2009 Share Posted October 22, 2009 The next thing to describe is the concept of charge? Take care, chbare. Link to comment Share on other sites More sharing options...
chbare Posted October 22, 2009 Author Share Posted October 22, 2009 Right, specifically why does sodium have a +1 charge and why does chloride have a -1 charge? What determines a positive ion (cation) versus negative ion (anion) and what dictates the actual charge? I will leave the transition metals out of this discussion for the sake of simplicity however. Take care, chbare. Link to comment Share on other sites More sharing options...
armymedic571 Posted October 22, 2009 Share Posted October 22, 2009 (edited) Oh lets see..... Without looking it up, I would say it has something to do with the amount of covalence bonds the molecule has or does not have. Meaning does it have enough electrons (no charge), not enough electrons (positive charge), or too many electrons (negative charge). Depending on a molecules charge, it can determine what and how many other molecules it can or cannot bond with, or what kind of bond it can form. But..... that is all I can remember at 0430 in the AM. Over to you chbare...... Edited October 22, 2009 by armymedic571 Link to comment Share on other sites More sharing options...
chbare Posted October 22, 2009 Author Share Posted October 22, 2009 Oh lets see..... Without looking it up, I would say it has something to do with the amount of covalence bonds the molecule has or does not have. Meaning does it have enough electrons (no charge), not enough electrons (positive charge), or too many electrons (negative charge). Depending on a molecules charge, it can determine what and how many other molecules it can or cannot bond with, or what kind of bond it can form. But..... that is all I can remember at 0430 in the AM. Over to you chbare...... You are on the right track. Atoms bind and interact through two broad categories: Covalent bonds & non covalent bonds. When we talk about sodium chloride, we are talking about a type of non covalent bond known as an ionic bond. Let's explore this concept of an ion. Do not worry, I intend to bring this back around to the question at hand. Atoms are composed of three "gross" parts. You have neutrons and protons in the nucleus and electrons outside of the nucleus. Electrons are negatively charged and protons are positively charged. Therefore, an atom in it's "natural" state will have the same number of electrons as protons in order to have a neutral overall charge. Unfortunately, electrons are fickle and like to have an arrangement that is "stable" The electrons in the outermost "shell" (this is called the valence, and we call these electrons valence electrons) of the atom want to meet what is called the octet rule. This is, atoms are very happy when they have eight electrons in their valence. (Exceptions are few and far between and include elements like hydrogen that only has 2 electrons in its valence; however, the first shell can only contain 2 electrons, therefore it is full and considered stable.) So, in an ionic bond or ionized situation, atoms either gain or loose electrons to meet this octet rule. I want you to look at the table below: The periodic table is very helpful with understanding these concepts. The periodic table is roughly divided into horizontal rows called periods and vertical rows called groups. The information from this arrangement is quite helpful. Let's look at sodium: Sodium is Na on the far left of the table. The number above Na is called the atomic number and this tells us how many protons are in a sodium atom. The atomic number is analogues to a fingerprint. Every element will have a unique atomic number. So, if sodium has 11 protons, it must have 11 electrons. Now, let's look at period and group. If you count down, sodium is in the third period. This means that sodium has three shells of electrons around it's nucleus. While it is not stated, sodium is a group 1A element. This means that there is one electron in sodiums valence. Therefore: the electron arrangement would look like this: first shell (2) (most that can fit in the first), 8 electrons in the second, 1 electron in the third. So, for sodium to meet the octet rule, what has to occur? You may have guessed it, sodium looses the electron in it's valence, and now the octet rule is met. So, if sodium looses a negative charge (electron), the overall charge of sodium is now positive. This is why sodium is positively charged as an ion and why it's called a cation. Anybody want to work out what happens to chlorine when it becomes ionized? Take care, chbare. Link to comment Share on other sites More sharing options...
RavEMTGun Posted October 23, 2009 Share Posted October 23, 2009 Happy Mole Day everyone. "Celebrated annually on October 23 from 6:02 a.m. to 6:02 p.m., Mole Day commemorates Avogadro's Number (6.02 x 10^23), which is a basic measuring unit in chemistry. Mole Day was created as a way to foster interest in chemistry. Schools throughout the United States and around the world celebrate Mole Day with various activities related to chemistry and/or moles. For a given molecule, one mole is a mass (in grams) whose number is equal to the atomic mass of the molecule. For example, the water molecule has an atomic mass of 18, therefore one mole of water weighs 18 grams. An atom of neon has an atomic mass of 20, therefore one mole of neon weighs 20 grams. In general, one mole of any substance contains Avogadro's Number of molecules or atoms of that substance. This relationship was first discovered by Amadeo Avogadro (1776-1858) and he received credit for this after his death." http://en.wikipedia.org/wiki/Mole_Day Link to comment Share on other sites More sharing options...
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