Atom – the smallest unit of matter “indivisible” Helium atom

electron shells a)Atomic number = number of Electrons b)Electrons vary in the amount of energy they possess, and they occur at certain energy levels or electron shells. c)Electron shells determine how an atom behaves when it encounters other atoms

Electrons are placed in shells according to rules: 1)The 1st shell can hold up to two electrons, and each shell thereafter can hold up to 8 electrons.

Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 electrons C would like to N would like to O would like to Gain 4 electrons Gain 3 electrons Gain 2 electrons

Why are electrons important? 1)Elements have different electron configurations  different electron configurations mean different levels of bonding

Electron Dot Structures Symbols of atoms with dots to represent the outermost shell electrons H  He:            Li  Be   B   C   N   O  : F  : Ne :                    Na  Mg   Al   Si   P   S  : Cl  : Ar :        

Chemical bonds: an attempt to fill electron shells 1.Ionic bonds – 2.Covalent bonds – 3.Metallic bonds

Learning Check A. X would be the electron dot formula for 1) Na2) K3) Al B. X would be the electron dot formula 1) B2) N3) P

IONIC BOND bond formed between two ions by the transfer of electrons

Formation of Ions from Metals Ionic compounds result when metals react with nonmetals Metals lose electrons to match the number of valence electrons of their nearest noble gas Positive ions form when the number of electrons are less than the number of protons Group 1 metals  ion 1+ Group 2 metals  ion 2+ Group 13 metals  ion 3+

Formation of Sodium Ion Sodium atom Sodium ion Na  – e   Na ( = Ne) 11 p + 11 p + 11 e - 10 e

Formation of Magnesium Ion Magnesium atom Magnesium ion  Mg  – 2e   Mg (=Ne) 12 p + 12 p + 12 e- 10 e

Some Typical Ions with Positive Charges (Cations) Group 1Group 2Group 13 H + Mg 2+ Al 3+ Li + Ca 2+ Na + K +

Learning Check A. Number of valence electrons in aluminum 1) 1 e - 2) 2 e - 3) 3 e - B. Change in electrons for octet 1) lose 3e - 2) gain 3 e - 3) gain 5 e - C.Ionic charge of aluminum 1) 3- 2) 5- 3) 3 +

Solution A. Number of valence electrons in aluminum 3) 3 e - B. Change in electrons for octet 1) lose 3e - C.Ionic charge of aluminum 3) 3 +

Learning Check Give the ionic charge for each of the following: A. 12 p + and 10 e - 1) 02) 2+3) 2- B. 50p + and 46 e- 1) 2+2) 4+3) 4- C. 15 p + and 18e- 2) 3+ 2) 3-3) 5-

Ions from Nonmetal Ions In ionic compounds, nonmetals gain electrons from metals Nonmetal add electrons to achieve the octet arrangement Nonmetal ionic charge: 3-, 2-, or 1-

Fluoride Ion unpaired electronoctet     1 - : F  + e  : F :     (= Ne) 9 p+ 9 p + 9 e- 10 e ionic charge

Ionic Bond Between atoms of metals and nonmetals Bond formed by transfer of electrons Produce charged ions. Conductors and have high melting point. Examples; NaCl, CaCl 2, K 2 O

1). Ionic bond – electron from Na is transferred to Cl, this causes a charge imbalance in each atom. The Na becomes (Na+) and the Cl becomes (Cl-), charged particles or ions.

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COVALENT BOND bond formed by the sharing of electrons

Covalent Bond Between nonmetallic elements Formed by sharing electron pairs Stable non-charged particles, they are not conductors at any state Examples; O 2, CO 2, C 2 H 6, H 2 O, SiC

Bonds in all the polyatomic ions and diatomics are all covalent bonds

when electrons are shared equally COVALENT BOND in elements H 2 or Cl 2

2. Covalent bonds- Two atoms share one or more pairs of outer-shell electrons. Oxygen Atom Oxygen Molecule (O 2 ) Oxygen Molecule (O 2 )

when electrons are shared but shared unequally COVALENT BONDS in compounds H2OH2O

- water is a polar molecule because oxygen is more electronegative than hydrogen, and therefore electrons are pulled closer to oxygen.

METALLIC BOND bond found in metals; holds metal atoms together very strongly

Metallic Bond Formed between atoms of metallic elements Electron cloud around atoms Good conductors at all states, lustrous, very high melting points Examples; Na, Fe, Al, Au, Co

Ionic Bond, A Sea of Electrons

Metals Form Alloys Metals do not combine with metals. They form Alloys which is a solution of a metal in a metal. Examples are steel, brass, bronze and pewter.

Compounds and Their Bonds Ionic Compounds Naming Ionic Formulas

Ionic Compounds Attraction between + ions and - ions Electrons go from metals to nonmetals electron transfer metal nonmetal ion + ion – Electrons lost = Electrons gain

Formulas of Ionic Compounds Formulas of ionic compounds are determined from the charges on the ions atoms ions     – Na  +  F :  Na + : F :  NaF     sodium fluorine sodium fluoride formula Charge balance: = 0

Writing a Formula Write the formula for the ionic compound that will form between Ba 2+ and Cl . Solution: 1. Balance charge with + and – ions 2. Write the positive ion of metal first, and the negative ion Ba 2+ Cl  Cl  3. Write the number of ions needed as subscripts BaCl 2

Learning Check Write the correct formula for the compounds containing the following ions: A. Na +, S 2- 1) NaS 2) Na 2 S3) NaS 2 B. Al 3+, Cl - 1) AlCl 3 2) AlCl 3) Al 3 Cl C. Mg 2+, N 3- 1) MgN 2) Mg 2 N 3 3) Mg 3 N 2

Solution A. Na +, S 2- 2) Na 2 S B. Al 3+, Cl - 1) AlCl 3 C. Mg 2+, N 3- 3) Mg 3 N 2

Naming Binary Ionic Compounds Contain 2 different elements Name the metal first, then the nonmetal as -ide. Use name of a metal with a fixed charge Groups 1A, 2A, 3A and Ag, Zn, and Cd Examples: NaClsodium chloride ZnI 2 zinc iodide Al 2 O 3 aluminum oxide

Learning Check Complete the names of the following binary compounds: Na 3 Nsodium ________________ KBrpotassium________________ Al 2 O 3 aluminum ________________ MgS_________________________

Solution Complete the names of the following binary compounds: Na 3 Nsodium nitride KBrpotassium bromide Al 2 O 3 aluminum oxide MgSmagnesium sulfide

Learning Check A. The formula for the ionic compound of Na + and O 2- is 1) NaO2) Na 2 O3) NaO 2 B. The formula of a compound of aluminum and chlorine is 1) Al 3 Cl2) AlCl 2 3) AlCl 3 C. The formula of Fe 3+ and O 2- is 1) Fe 3 O 2 2) FeO 3 3) Fe 2 O 3

Solution A. The formula for the ionic compound of Na + and O 2- is 2) Na 2 O B. The formula of a compound of aluminum and chlorine is 3) AlCl 3 C. The formula of Fe 3+ and O 2- is 3) Fe 2 O 3

Learning Check Name the following compounds: A. CaO 1) calcium oxide2) calcium(I) oxide 3) calcium (II) oxide B. SnCl 4 1) tin tetrachloride2) tin(II) chloride 3) tin(IV) chloride C. Co 2 O 3 1) cobalt oxide 2) cobalt (III) oxide 3) cobalt trioxide

Solution Name the following compounds: A. CaO1) calcium oxide B. SnCl 4 3) tin(IV) chloride C.Co 2 O 3 2) cobalt (III) oxide