Drawing Atoms & Chemical Bonding September 9, 2015September 9, 2015September 9, 2015

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

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

Electron Energy Levels The atoms have the outermost energy level filled. 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. 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. ____________ electrons represent the number of electrons in the outer energy level. most stable Valence

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

CHEMICAL BONDS When two or more elements come together, they form a compound. When two or more elements come together, they form a compound. Compounds are held together by forces called chemical bonds. 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. 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. 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. 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. 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 When an atom gains an electron from another atom, it ends up with more electrons with protons. This results in an overall ___________ charge. 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. Ions – electrically charged atoms. (Ex) Na+ or Cl - negative

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

Types of Bonding Covalent bond – a bond based on the attraction between atoms that share electrons. (Ex) Water –H 2 O Covalent bond – a bond based on the attraction between atoms that share electrons. (Ex) Water –H 2 O

Covalent Bonding (Water Molecule) H 2 O H 2 O 8 P 8 N Hydrogen Oxygen 1 P

Review Questions In water, how many electrons does oxygen share with each hydrogen atom? In water, how many electrons does oxygen share with each hydrogen atom? What kind of bond is this? What kind of bond is this? How many valence electrons does sodium have? How many valence electrons does sodium have? How many valence electrons does chlorine have? How many valence electrons does chlorine have? Describe what happens when sodium bonds with chlorine. 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? 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? 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. What is the charge of a teaspoon of salt (NaCl) crystals? Explain. An Ionic Bond Eight Neutral