Drawing Atoms & Chemical Bonding April 13, 2015 Electron Energy Levels Electrons are arranged in within the electron cloud. Each energy level can hold a certain maximum number of electrons. 2 First level – ____ 8 Second level – ____ 8 Third level – ____ Drawing an Atom Fluorine Atom (F) 9P 10 N How many electrons does a Fluorine atom have? 9 _______ Electron Energy Levels most stable atoms have the The outermost energy level filled. Atoms in which the outermost energy level is filled does not easily gain or lose electrons, therefore they do not easily form compounds with other elements. ____________ electrons represent the number of electrons in the outer energy level. Drawing an Atom I’m Stable Neon Atom (Ne) 10 P 10 N Go away, I don’t want to BOND with anyone. How many electrons does a Neon atom have? 10 _______ CHEMICAL BONDS When two or more elements come together, they form a compound. Compounds are held together by forces called chemical bonds. Atoms can form chemical bonds by sharing electrons or by transferring electrons from one atom to another. Types of Bonds When a compound is formed through the transfer of electrons, this is called an ionic bond. Most ionic compounds are formed by the transfer of electrons from a metal to a nonmetal. When an atom loses an electron to move to another atom, it ends up with more protons than positive electrons. This results in an overall __________ charge. Types of Bonding When an atom gains an electron from another atom, it ends up with more electrons with protons. This results in an negative overall ___________ charge. Ions – electrically charged atoms. (Ex) Na+ or Cl Cl Now, the Na gives or transfers its one extra electron to Cl Na 17P 11P 18N 12N Types of Bonding Covalent bond – a bond based on the attraction between atoms that share electrons. (Ex) Water –H2 O Covalent Bonding (Water Molecule) H 2O 1P Hydrogen 8P Hydrogen 8N 1P Oxygen Review Questions In water, how many electrons does oxygen share with each hydrogen atom? One What kind of bond is this? Covalent Bond How many valence electrons does sodium have? One How many valence electrons does chlorine have? Seven Describe what happens when sodium bonds with chlorine. Review Questions What kind of bond is formed between Na and Cl? An Ionic Bond After the bond between sodium and chlorine forms, how many electrons does sodium have in the resulting outer layer? Eight What is the charge of a teaspoon of salt (NaCl) crystals? Explain. Neutral