Chemical Bond

Slide 1: 

Chemical Bonds

Slide 2: 

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

electron shells : 

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. Electron shells determine how an atom behaves when it encounters other atoms

Electrons are placed in shells according to rules: : 

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.

Slide 5: 

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? : 

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

Electron Dot Structures : 

Electron Dot Structures Symbols of atoms with dots to represent the valence-shell electrons 1 2 13 14 15 16 17 18 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 : 

Chemical bonds: an attempt to fill electron shells Ionic bonds – Covalent bonds – Metallic bonds

Learning Check : 

Learning Check ? 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 BONDbond formed between two ions by the transfer of electrons : 

IONIC BONDbond formed between two ions by the transfer of electrons

Formation of Ions from Metals : 

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 : 

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 : 

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) : 

Some Typical Ions with Positive Charges (Cations) Group 1 Group 2 Group 13 H+ Mg2+ Al3+ Li+ Ca2+ Na+ Sr2+ K+ Ba2+

Learning Check : 

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 : 

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 : 

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 : 

Ions from Nonmetal Ions In ionic compounds, nonmetals in 15, 16, and 17 gain electrons from metals Nonmetal add electrons to achieve the octet arrangement Nonmetal ionic charge: 3-, 2-, or 1-

Fluoride Ion : 

Fluoride Ion 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 : 

Ionic Bond Between atoms of metals and nonmetals with very different electronegativity Bond formed by transfer of electrons Produce charged ions all states. Conductors and have high melting point. Examples; NaCl, CaCl2, K2O

Slide 24: 

Ionic Bonds: One Big Greedy Thief Dog!

Slide 25: 

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.

COVALENT BONDbond formed by the sharing of electrons : 

COVALENT BONDbond formed by the sharing of electrons

Covalent Bond : 

Covalent Bond Between nonmetallic elements of similar electronegativity. Formed by sharing electron pairs Stable non-ionizing particles, they are not conductors at any state Examples; O2, CO2, C2H6, H2O, SiC

Slide 29: 

Covalent Bonds

Slide 30: 

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

when electrons are shared equally : 

when electrons are shared equally NONPOLAR COVALENT BONDS H2 or Cl2

Slide 32: 

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 : 

when electrons are shared but shared unequally POLAR COVALENT BONDS H2O

Slide 34: 

Polar Covalent Bonds: Unevenly matched, but willing to share.

Slide 35: 

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

METALLIC BONDbond found in metals; holds metal atoms together very strongly : 

METALLIC BONDbond found in metals; holds metal atoms together very strongly

Metallic Bond : 

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

Slide 38: 

Metallic Bonds: Mellow dogs with plenty of bones to go around.

Ionic Bond, A Sea of Electrons : 

Ionic Bond, A Sea of Electrons

Metals Form Alloys : 

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.

Formula Weights : 

Formula Weights Formula weight is the sum of the atomic masses. Example- CO2 Mass, C + O + O 12.011 + 15.994 + 15.994 43.999

Practice : 

Practice Compute the mass of the following compounds round to nearest tenth & state type of bond: NaCl; 23 + 35 = 58; Ionic Bond C2H6; 24 + 6 = 30; Covalent Bond Na(CO3)2; 23 + 2(12 + 3x16) = 123; Ionic & Covalent