Documents about Valence Electrons

  • 2 Pages

    lecture 2

    University of Texas, CH 318M

    Excerpt: ... nfiguration of sodium cation is 1s22s2sp6, which is neon-like. The electronic configuration of fluoride anion is also 1s22s2sp6, which is neon-like. Thus, formation of our product is driven by the ability to achieve a filled electronic shell. In general, to assess reactivity only the valence electrons need be considered, i.e. you can ignore inner shell electrons. To draw the Lewis structure of an atom, ignore the inner shell electrons. Just draw the atomic symbol and depict the valence electrons as dots. Using this protocol, we drew Lewis structures for H2, F2 and HF. Note that bonding pairs of electrons are depicted as lines. Having drawn Lewis structures for H2, F2 and HF, we briefly reviewed the concept of bond polarity and dipole moment. Know the trends in electronegativity (and why) and be able to use this knowledge to predict bond dipoles and identify ionic bonds, pure covalent bonds and polar covalent bonds. Rules for drawing Lewis structures of more complex molecules. The ...

  • 3 Pages


    American River, CHEM 400-401

    Excerpt: ... Chem 400 Chapter 6 Lecture Notes Part 1 Ions and their Electron Configurations, and Radii You already learned how to write the electron configurations and the Noble Gas electron configurations for ions. Just remember that it is the valence electrons which get removed or added to first! So you always add to or remove from the highest energy level, or n value. Write the electron configurations and Noble Gas electron configurations for Cl-, Ca2+, and Mn2+. Can you see why metals tend to lose electrons and why nonmetals tend to gain electrons? What kind of electron configuration are they trying to obtain? And how many valence s and p electrons is this? Ionic Radii When a neutral atom of Li loses its valence 2s1 electron, what happens to the size of the Li+ cation? Is it smaller or larger than Li? Why is it smaller (think of Zeff, the effective nuclear charge and what shell the electron is lost from)? Likewise, if an oxygen atom gains 2 electrons to become O2-, what about the size of the ...

  • 25 Pages

    Review Session 1

    FSU, BSC 2010

    Excerpt: ... c arrangement and complexity of parts Example: NaCl Na = Cl = NaCl = = Atoms The atomic # = number of protons In an uncharged atom, the number of protons = number of electrons Atomic weight roughly = # protons + # neutrons Isotopes Same element, (ergo, same # protons) but different # neutrons Some isotopes are radioactive, in which the nucleus decays, giving off particles and energy These radioactive isotopes can be useful for scientific research Electrons H, C, N, O, P, S - important biological elements, you'll need to know for this class. Be able to recognize/draw the electron-shell diagrams given in the lecture notes! Valence electrons are those in the outermost shell. Chemical behavior of the atom is determined mostly by valence electrons , because they have the most energy and only the valence shell can be unfilled. Covalent Bonding When two atoms share a valence electron, a molecule is formed A single covalent bond is the sharing of a pair of electrons A ...

  • 46 Pages


    Mines, CHGN 222

    Excerpt: ... anic salt ammonium cyanate into organic substance "urea" 5 Organic chemistry is study of carbon compounds. Why is it so special? - 90% of more than 30 million chemical compounds contain carbon. - Examination of carbon in periodic chart answers some of these questions. - Formation of C-C bonds unique. - Carbon is group 4A element, it can share 4 valence electrons and form 4 covalent bonds. 6 Why this chapter? Review ideas from general chemistry: atoms, bonds, molecular geometry 7 1.1 Atomic Structure Structure of an atom Positively charged nucleus (very dense, protons and neutrons) and small (10-15 m) Negatively charged electrons are in a cloud (10-10 m) around nucleus Diameter is about 2 10-10 m (200 picometers (pm) [the unit angstrom () is 10-10 m = 100 pm] 8 Atomic Number and Atomic Mass The atomic number (Z) is the number of protons in the atom's nucleus The mass number (A) is the number of protons plus neutrons All the atoms of a given element ...

  • 3 Pages


    Vermont, CHEM 131

    Excerpt: ... 8 Lecture 5, January 25, 2008 III. Why are Valence Electrons Important? A. Screening 1. Core electrons are closer to the nucleus, so more energy is required to separate them from the atom (since the nucleus has a positive charge, and energy is required to separate positive and negative charges). 2. Valence electrons don't experience as much positive charge, because the core electrons "block" some of it-they sit between the valence electrons and the nucleus, so they prevent the valence electrons from experiencing some of it. However, this blocking is not perfect, because the radial wavefunction (R2) does not go to zero until r (implying that the core electrons do not spend 100% of their time between the nucleus and the valence electrons ). B. Slater's rules 1. These are a set of rules used to calculate how much positive charge is experienced by each electron in an atom. It makes approximations about how effective the screening of each orbital is, based primarily on the quantum numbers n and l. 2. It uses a f ...

  • 3 Pages


    American River, CHEM 400-401

    Excerpt: ... to decompose the salt into the metal and chlorine gas. K, Rb, and Cs are produced at very high temperatures via single displacement rxns. The Alkaline Earth Metals The alkaline earth metals of Group 2 all have 2 valence electrons with the configuration ns2. Although they have low IE1 values, their IE2 values are much higher. However the Lattice energy for their ionic compounds is very high as their +2 cations are small and have a high + charge. So they lose their 2 valence electrons easily to form +2 cations. So they form ionic compounds readily and they are strong reducing agents. They are the second most reactive metal Group, and reactivity increases going down the Group. So actually Ca, Ba and Sr are more reactive than Na in most circumstances. Like the Alkali Metals they are strong metals with a silvery appearance, but they are generally harder than the Alkali Metals (but still softer than most metals). They also have low melting points and densities, but they are higher than the Alka ...

  • 2 Pages


    Berkeley, CHEM 3A

    Excerpt: ... CHEM 3A Problem Set 1 (January, 24 2007) NOTE: No problem sets will be turned in for 3A lecture! Write out the ground-state electron configuration for the following atoms and identify how many valence electrons each has: a) Magnesium b) Calcium c) Bromine d) sulfur e) Boron f) Silicon Guess at what the most likely value for X is in the following molecules: a) AlClX b) NIX c) CClXF Lithium methoxide, LiOCH3, has both ionic and covelent bonds in it. Draw its Lewis structure and identify which bonds are ionic and which are covalent. ...

  • 4 Pages

    Lecture 6 NotesThe Periodic Table and Atomic Co...

    University of Texas, CH 53750

    Excerpt: ... me other general things to remember about electronic shielding include: You should remember that the above discussion is only a rough approximation. Not all inner shell electrons will shield effectively. You must remember that, in terms of penetration to the nucleus, that s > p > d > f (this is because there is a greater probability of finding an s-electron at the nucleus than for a p-electron, etc). Atomic Radius We would like to use the P.T. to assign general trends. One trend we are interested in is the atomic radius, or the size of the atom. In general, atomic radius (A.R.) will increase as one goes down a group in the P.T., and it will decrease as you go across a period. The reasons for this: A.R. increases as you go down a group because the valence electrons will lie in higher principle quantum number shell n. Remember that n is a measure of both i) the energy of the electron in the atom, and ii) the average distance of the electron in the nucleus. Lithium would have a smaller A.R. than Cesium because L ...

  • 16 Pages


    UWO, CHEM 020

    Excerpt: ... that only electrons in the valence shell are involved in the formation of covalent bonds. Suppose we have two H atoms forming molecular hydrogen: H(g) + H(g) This is favourable because: o The two electrons in the bond are simultaneously attracted to both nuclei. o The pairing of electrons with opposite spin reduces the energy of the system We use electron-dot structures to show electrons and bonds: H2(g) H = Each bond contains two electrons (one electron pair). In order for bonds to form, orbital overlap must occur. In this case, the 1s orbital from each H atom overlaps. 13.3 Since each H atom has the configuration 1s1 (one electron in the valence shell), it can only form one bond. H H H Cl H O H What if there is more than one electron in the valence shell, for example, with oxygen in water above? Such atoms can form more than one bond, but the exact number of bonds formed is predicted by Lewis structures. o The number of valence electrons surrounding a nonmetal should be equal t ...