Atomic Configuration & Bonding © Copyright NewPath Learning. All Rights Reserved. 94-4837 Visit www.newpathlearning.com for Online Learning Resources. Electron Configuration The specific way the electrons are arranged in an atom is called the electron configuration. Electrons play an important role in how elements interact with each other and form compounds. The electrons are distributed among orbital shells or energy levels (1, 2, 3 and so on) that are different distances from the nucleus. The larger the number of the energy level, the farther it is from the nucleus. Electrons that are in the highest or outmost energy level are called valence electrons. The valence electrons are the ones that are lost, gained or shared during chemical bonding. Oxygen atom (neutral) electrons orbital shell 1 orbital shell 2 atomic number = 8 protons = 8 electrons = 8 electron cloud nucleus valence electron valence shell Br 35 Bromine Cl 17 Chlorine F 9 Fluorine I 53 Iodine At 85 Astatine Li 3 Lithium Na 11 Sodium K 19 Potassium Rb 37 Rubidium Cs 55 Cesium Alkali metals • 1 valence electron • lose electron Halogens • 7 valence electrons • gain electron Sodium Chlorine Aluminum Oxygen Atoms with 4 or more valence electrons gain electrons. Atoms with 3 or less valence electrons lose electrons. Atoms with full valence shells will not combine with other elements. Neon Electron Dot Diagram The number of valence electrons in an atom of an element determines many properties of that element, including the ways in which the atom can bond with other atoms. An electron dot diagram is often used to depict the valence electrons in an atom. Each atom of an element has a specific number of valence electrons, ranging from 1 to 8. The electron dot diagram includes the element symbol, surrounded by dots. Each dot represents 1 valence electron. The dots are spaced out above, below, to the left, and to the right of the symbol for the first 4 valence electrons. For atoms with greater than 4 valence electrons, the dots must be paired up. The dot diagrams for atoms can also be used to show the bond between different atoms in a molecule. C O Ar valence electrons Carbon Oxygen Argon He 2 Helium Ne 10 Neon Ar 18 Argon Kr 36 Krypton Xe 54 Xenon Rn 86 Radon Argon Neon Krypton Noble gases • 8 valence electrons Stability of Atoms Atoms of most elements are more stable and are less likely to react with other atoms, when they have 8 valence electrons in their outer shell. For example, atoms of neon, argon, krypton, and xenon are very unreactive because they all have 8 valence electrons. Atoms usually react in a way that makes each atom more stable by losing, gaining, or sharing electrons in a chemical bond with other atoms. Valence Electrons & Bonding The outermost orbital shell, called the valence shell, is most often involved in chemical bonding. Elements in the same group in the periodic table have the same number of electrons in their valence shell. For example, all elements in group 1, alkali metals, have 1 valence electron. Group 1 atoms prefer to lose 1 electron to become stable. However, all elements in group 17, halogens, have 7 valence electrons. These atoms will gain 1 electron to fill their valence shell.
Pause and Review Fill in the table below. Group # C Cu Be O Xe # of electrons # of valence electrons Element (neutral) Use the information in the illustrations to answer the questions. Select the best answer(s) and then click on the check button. Please make the buttons as large as possible so they can count electrons Na F Ne O 1) Which element has 1 valence electron? ________________________________ 2) Which element is most reactive? ______________________________________ 3) Which element has a full valence shell? ________________________________ 4) Which element is the most stable? ____________________________________ 5) Which element has 6 valence electrons? _______________________________ 6) Which element has 7 valence electrons? _______________________________ Atomic Configuration & Bonding © Copyright NewPath Learning. All Rights Reserved. 94-4837 Visit www.newpathlearning.com for Online Learning Resources.