CHAPTER 6 CHEMICAL BONDING

S ECTION 1 Ionic Bonding

V OCABULARY Electron dot diagram Ion Anion Cation Chemical bond Ionic bond Chemical formula crystals

S TABLE ELECTRON CONFIGURATIONS When the highest occupied energy level of an atom is filled with electrons, the atom is stable and not likely to react…. Noble Gases!! Electron Dot Diagram: model of an atom where each dot represents a valence electron Some elements achieve stable electron configurations through the transfer of electrons between atoms.

IONIC BONDS ION: an atom that has a net positive or negative charge….Cl- Na+ ANION: AN ION WITH A NEGATIVE CHARGE….Cl-… it had to take one CATION: AN ION WITH A POSITIVE CHARGE….Na+… it gave one away CHEMICAL BOND: force that holds atoms or ions together as a unit. IONIC BOND: force that holds cations and anions together….an ionic bond forms when electrons are transferred from one atom to another.

FORMATION OF IONIC BONDS IONIZATION ENERGY: amount of energy used to remove an electron…varies from element to element…lower ionization energy = easy electron removal. CHEMICAL FORMULA: notation that shows what elements a compound contains and the ratio of the atoms or ions in the compound.

SECTION 2 COVALENT BONDING

VOCABULARY COVALENT BOND MOLECULE POLAR COVALENT BOND

COVALENT BONDS 1 OF 2 COVALENT BOND: a chemical bond in which two atoms share a pair of valence electrons. The attractions between the shared electrons and the protons in each nucleus hold the atoms together in a covalent bond= MOLECULE 2 covalent bonds between atoms = double bond……3 covalent bonds between atoms = triple bond Polar Covalent Bond: electrons are not shared equally

When atoms form a polar covalent bond, the atom with the greater attraction for electrons has a partial negative charge. The other atom will have a partial positive charge THE TYPE OF ATOMS IN A MOLECULE AND ITS SHAPE ARE FACTORS THAT DETERMINE WHETHER A MOLECULE IS POLAR OR NONPOLAR.

SECTION 3 NAMING COMPOUNDS AND WRITING FORMULAS

VOCABULARY POLYATOMIC ION

DESCRIBING IONIC COMPOUNDS Chemists use a system for naming compounds based on composition…the chemical formula for sodium chloride is NaCl…a 1 to 1 ratio of sodium and chlorine atoms. The name of an ionic compound must distinguish it from other compounds containing the same elements…the formula of an ionic compound describes the ratio of ions in the compound

B INARY IONIC COMPOUNDS These compounds made up of only 2 atoms The Latin prefix bi- means two Names have a predictable pattern: cation first, followed by the anion changing the ending to –ide KI = potassium iodide The subscript number following each element symbol tells how many of each element are in the compound

M ETALS AND POLYATOMIC IONS Many transition metals have more than one ion that are represented by Roman numerals… copper I and copper II See chart top of pg 172 See chart top of pg 172 A covalently bonded group of atoms is called a polyatomic ion. Prefix poly- means ‘many’ Sometimes there are parenthesis ( ) around the polyatomic ion in a formula See chart bottom pg 173 See chart bottom pg 173

MOLECULAR COMPOUNDS The name and formula of a molecular compound describe the type and number of atoms in a moleucle of the compound More metallic elements are listed first in the name….. USE CHART ON PG 175!!!!

S ECTION 4 THE STRUCTURE OF METALS

VOCABULARY METALLIC BOND ALLOY

METALLIC BONDS Metallic Bond: attraction between a metal cation and shared electrons around it The cations in a metal form a lattice that is held in place by strong metallic bonds between the cations and the surrounding valence electrons. The more valence electrons contributed to the bond the stronger it will be.

PROPERTIES OF METALS The mobility of electrons within a metal lattice explains some of the properties of metals….. conductivity/malleability

ALLOYS Alloys: are a mixture of two or more elements, at least one of which is a metal…alloys have properties of metals Copper alloys: BRONZE = COPPER + TIN BRASS = COPPER + ZINC ALLOYS ARE DESIGNED WITH SPECIFIC PROPERTIES IN MIND BASED ON THE AMOUNT OF ELEMENTS NEEDED.