I’m Bond, Chemical Bond

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

electron shells Atomic number = number of Electrons Electrons vary in the amount of energy they possess, and they occur at certain energy levels or electron shells.

Electrons are placed in shells according to rules: 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? Elements have different electron configurations different electron configurations mean different ways of bonding – and different products from their reactions

Noble gases

Electron Dot Structures Symbols of atoms with dots to represent the outermost shell electrons 1 2 3 4 5 6 7 2/8 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 Ionic bonds – Covalent bonds – Metallic bonds

Learning Check A. X would be the electron dot formula for  A. X would be the electron dot formula for 1) Na 2) K 3) Al   B.  X  would be the electron dot formula 1) B 2) N 3) 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 outermost shell 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 + 2-8-1 2-8 ( = Ne) 11 p+ 11 p+ 11 e- 10 e- 0 1+

Formation of Magnesium Ion Magnesium atom Magnesium ion  Mg  – 2e  Mg2+ 2-8-2 2-8 (=Ne) 12 p+ 12 p+ 12 e- 10 e- 0 2+

Some Typical Ions with Positive Charges (Cations) Group 1 Group 2 Group 13 H+ Mg2+ Al3+ Li+ Ca2+ Na+ K+

Learning Check A. Number of outermost shell electrons in aluminium 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 aluminium 1) 3- 2) 5- 3) 3+

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

Learning Check Give the ionic charge for each of the following: A. 12 p+ and 10 e- 1) 0 2) 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     1 - : F  + e : F :     2-7 2-8 (= Ne) unpaired electron octet     1 - : F  + e : F :     2-7 2-8 (= Ne) 9 p+ 9 p+ 9 e- 10 e- 0 1 - 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, CaCl2, K2O

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.

http://www.youtube.com/watch?v=Ftw7a5ccubs

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; O2, CO2, C2H6, H2O, SiC

Covalent Bonds

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

when electrons are shared equally COVALENT BOND in elements when electrons are shared equally H2 or Cl2

2. Covalent bonds- Two atoms share one or more pairs of outer-shell electrons. Oxygen Atom Oxygen Atom Oxygen Molecule (O2)

when electrons are shared but shared unequally COVALENT BONDS in compounds when electrons are shared but shared unequally H2O

- 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: 1+ 1- = 0

Writing a Formula Write the formula for the ionic compound that will form between Ba2+ and Cl. Solution: 1. Balance charge with + and – ions 2. Write the positive ion of metal first, and the negative ion Ba2+ Cl Cl 3. Write the number of ions needed as subscripts BaCl2

Learning Check Write the correct formula for the compounds containing the following ions: A. Na+, S2- 1) NaS 2) Na2S 3) NaS2 B. Al3+, Cl- 1) AlCl3 2) AlCl 3) Al3Cl C. Mg2+, N3- 1) MgN 2) Mg2N3 3) Mg3N2

Solution A. Na+, S2- 2) Na2S B. Al3+, Cl- 1) AlCl3 C. Mg2+, N3-

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: NaCl sodium chloride ZnI2 zinc iodide Al2O3 aluminum oxide

Learning Check Complete the names of the following binary compounds: Na3N sodium ________________ KBr potassium ________________ Al2O3 aluminum ________________ MgS _________________________

Solution Complete the names of the following binary compounds: Na3N sodium nitride KBr potassium bromide Al2O3 aluminum oxide MgS magnesium sulfide

Learning Check A. The formula for the ionic compound of Na+ and O2- is 1) NaO 2) Na2O 3) NaO2 B. The formula of a compound of aluminum and chlorine is 1) Al3Cl 2) AlCl2 3) AlCl3 C. The formula of Fe3+ and O2- is 1) Fe3O2 2) FeO3 3) Fe2O3

Solution A. The formula for the ionic compound of Na+ and O2- is 2) Na2O B. The formula of a compound of aluminum and chlorine is 3) AlCl3 C. The formula of Fe3+ and O2- is 3) Fe2O3

Learning Check 3) cobalt trioxide Name the following compounds: A. CaO 1) calcium oxide 2) calcium(I) oxide 3) calcium (II) oxide B. SnCl4 1) tin tetrachloride 2) tin(II) chloride 3) tin(IV) chloride C. Co2O3 1) cobalt oxide 2) cobalt (III) oxide 3) cobalt trioxide

Solution Name the following compounds: A. CaO 1) calcium oxide B. SnCl4 3) tin(IV) chloride C. Co2O3 2) cobalt (III) oxide

Q1. Name a metal in group 1 that is in the same period as Magnesium. Q2. Name a metal in group 2 that in the same period as Lithium. Q3. Name a non-metal in the same group as Nitrogen. Q4. Name a noble gas in the same period as Oxygen. Q5. Name a gas in group 7 that is in the same period as Aluminium.

Objective: 1. Learn the scientific method for naming compounds. 2. There are three rules for naming compounds: the “ide” rule, the “ate” rule and the “same” rule.

Rule 1: When two elements combine the ending is usually ” ……………ide” Rule 1: When two elements combine the ending is usually ” ……………ide”. metal goes first Sodium Chloride Magnesium Oxide Iron Sulphide Cl Na Mg O Fe S

Rule 2: When three or more different elements combine and one of them is Oxygen, the ending will be “………ate”. metal goes first Copper Sulphate Calcium Carbonate O O Cu S O O O O C Ca O

Rule 3: When two identical elements combine, the name does not change. H2 = Hydrogen F2 = Fluorine N2 = Nitrogen Cl2 = Chlorine O2 = Oxygen H F N Cl O

Name the following compound Na2O

Name the following compound CuSO4

Name the following compound MgSO4

Name the following compound ZnO

Name the following compound MgCl2

Name the following molecule

Name the following compound KI

Name the following compound AgNO3