Drawing Atoms & Chemical Bonding May 19, 2019

Electron Energy Levels Electrons are arranged in within the electron cloud. Each energy level can hold a certain maximum number of electrons. First level – ____ Second level – ____ Third level – ____ 2 8 8

Drawing an Atom Fluorine Atom (F) How many electrons does a Fluorine atom have? _______ 9 P 10 N 9

Electron Energy Levels Valence Electron Energy Levels most stable The atoms have 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.

Go away, I don’t want to BOND with anyone. Drawing an Atom I’m Stable Neon Atom (Ne) How many electrons does a Neon atom have? _______ 10 P 10 N Go away, I don’t want to BOND with anyone. 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 electrons. This results in an overall __________ charge. positive

Types of Bonding negative When an atom gains an electron from another atom, it ends up with more electrons with protons. This results in an overall ___________ charge. Ions – electrically charged atoms. (Ex) Na+ or Cl- negative

Now, the Na gives or transfers its one extra electron to Cl Cl Na Now, the Na gives or transfers its one extra electron to Cl 11P 12N 17P 18N Now everyone is happy

Types of Bonding Covalent bond – a bond based on the attraction between atoms that share electrons. (Ex) Water –H2 O

Covalent Bonding (Water Molecule) H2O 1 P Hydrogen 8 P 8 N Hydrogen 1 P Oxygen

Review Questions In water, how many electrons does oxygen share with each hydrogen atom? What kind of bond is this? How many valence electrons does sodium have? How many valence electrons does chlorine have? Describe what happens when sodium bonds with chlorine. One Covalent Bond One Seven

Review Questions What kind of bond is formed between Na and Cl? After the bond between sodium and chlorine forms, how many electrons does sodium have in the resulting outer layer? What is the charge of a teaspoon of salt (NaCl) crystals? Explain. An Ionic Bond Eight Neutral