BondingBonding

Ionic and covalentIonic and covalent

Key TermsKey Terms11

Chemical formula– the combination of Chemical formula– the combination of chemical symbols and subscripts to chemical symbols and subscripts to indicate what the elements are in the indicate what the elements are in the compound and how many atoms of each compound and how many atoms of each element are in the compoundelement are in the compound Example: HExample: H22O= two hydrogen atoms and 1 O= two hydrogen atoms and 1

oxygen atom.oxygen atom.

Key TermsKey Terms22

The octet rule– each atom wants to have The octet rule– each atom wants to have 8 electron in its outer most energy level.8 electron in its outer most energy level. Atoms can share, take, or give away Atoms can share, take, or give away

electrons to accomplish this.electrons to accomplish this.

Valence electrons– electrons in the outer Valence electrons– electrons in the outer most energy level that are responsible for most energy level that are responsible for the reactivity of that atom.the reactivity of that atom.

Key TermsKey Terms33

Lewis structure (electron-dot notation)– Lewis structure (electron-dot notation)– valence electrons are shown as dots around valence electrons are shown as dots around the element’s symbol. Label the # of Ve- on the element’s symbol. Label the # of Ve- on your periodic table.your periodic table. Because each orbital can hold two electrons, Because each orbital can hold two electrons,

electrons are grouped in pairs forming the shape of electrons are grouped in pairs forming the shape of a box around the element’s symbol.a box around the element’s symbol.

Paired electrons can also be represented by a dash Paired electrons can also be represented by a dash instead of dots if they are being shared in a instead of dots if they are being shared in a compound.compound.

Key termsKey terms44

IonsIons Ion– any atom that has given up or taken Ion– any atom that has given up or taken

electrons to create a positive or negative electrons to create a positive or negative charge.charge.

This is done to fill the highest energy level.This is done to fill the highest energy level. Cations (cat-ion) – any element that has given Cations (cat-ion) – any element that has given

away its electrons to become a positively away its electrons to become a positively charged ion. Cations are metals.charged ion. Cations are metals.

Anions– any element that has taken electrons Anions– any element that has taken electrons to become a negatively charged ion. Anions to become a negatively charged ion. Anions are nonmetals.are nonmetals.

Atoms and chargesAtoms and charges What happens when an atom gains or looses What happens when an atom gains or looses

an electron?an electron? The atom becomes charged!The atom becomes charged!

Example: Copper has an atomic number of 29.Example: Copper has an atomic number of 29.This means copper has 29 electrons(-) and This means copper has 29 electrons(-) and

29 protons(+). If copper were to loose two 29 protons(+). If copper were to loose two electrons, what would copper’s charge be?electrons, what would copper’s charge be?

29 Protons (+)29 Protons (+)+ 27+ 27 Electrons (-) Electrons (-) 2 Protons left over, each proton has a positive 2 Protons left over, each proton has a positive

charge so the charge of copper would be +2!charge so the charge of copper would be +2!

Practice ProblemPractice Problem

Oxygen has an atomic number of 8 and Oxygen has an atomic number of 8 and an atomic mass of 16. How many an atomic mass of 16. How many neutrons does oxygen have?neutrons does oxygen have?

Answer: 16= N+8, N=8Answer: 16= N+8, N=8 What would Oxygen’s charge be if it What would Oxygen’s charge be if it

gained two electrons?gained two electrons? Answer: 8(+ protons) + 10 (- electrons)=-Answer: 8(+ protons) + 10 (- electrons)=-

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Ionic BondingIonic Bonding

Ionic BondingIonic Bonding Ionic bonding– any bond between metals Ionic bonding– any bond between metals

and nonmetals (cations and anions)and nonmetals (cations and anions) Charges are based on how many Ve- are Charges are based on how many Ve- are

needed to fill the outer shell or drop to the needed to fill the outer shell or drop to the previous full shell. Label this on your table.previous full shell. Label this on your table.

The charges must cancel each other out.The charges must cancel each other out. Example: Na (+1) and Cl (-1)=NaCl (0)Example: Na (+1) and Cl (-1)=NaCl (0) Example: Ca (+2) and F (-1)=CaFExample: Ca (+2) and F (-1)=CaF22 (0) (0)

Ionic compounds are usually solids and in a Ionic compounds are usually solids and in a crystal structure (crystal lattice).crystal structure (crystal lattice).

Ionic CompoundsIonic Compounds Both ions should have complete outer shells Both ions should have complete outer shells

after bonding.after bonding. Both elements should have noble gas Both elements should have noble gas

electron configurationselectron configurations When naming, the first element always When naming, the first element always

stays the same, but the last element should stays the same, but the last element should end with –ideend with –ide Ex. MgO= Magnesium OxEx. MgO= Magnesium Oxideide instead of instead of

Magnesium OxygenMagnesium Oxygen Ex. CaClEx. CaCl22= Calcium Chlor= Calcium Chlorideide vs Chlorine vs Chlorine

Covalent Bond Key Covalent Bond Key TermsTerms11 Molecule: a group of atoms held together by Molecule: a group of atoms held together by covalent bondscovalent bonds

Covalent bond: when atoms share electronsCovalent bond: when atoms share electrons Nonpolar covalent bond: electrons are Nonpolar covalent bond: electrons are

equally shared by all atoms and the equally shared by all atoms and the electrical charge is balancedelectrical charge is balanced

Polar covalent bond: electrons are not Polar covalent bond: electrons are not shared equally and there is an imbalance in shared equally and there is an imbalance in the electrical charge surrounding the the electrical charge surrounding the molecule.molecule.

Polar vs. nonpolarPolar vs. nonpolar PolarPolar nonpolarnonpolar

Key TermsKey Terms22

Polar bonds: when atoms in a molecule Polar bonds: when atoms in a molecule have an uneven electron distribution.have an uneven electron distribution.

Bond length: average distance between two Bond length: average distance between two bonded atomsbonded atoms

Bond energy: energy required to break a Bond energy: energy required to break a chemical bond and form neutral isolated chemical bond and form neutral isolated atoms.atoms.

When the bond length gets shorter, the When the bond length gets shorter, the bond energy gets higherbond energy gets higher

Key TermsKey Terms33

Lewis structures must be used to create Lewis structures must be used to create covalent compounds (molecules). covalent compounds (molecules). Sorry no short Sorry no short cuts this time.cuts this time.

Single bond: when only two electrons are Single bond: when only two electrons are being shared between two atomsbeing shared between two atoms

Double bond: when 4 electrons are being Double bond: when 4 electrons are being shared between two atomsshared between two atoms

Triple bond: when 6 electrons are being Triple bond: when 6 electrons are being shared between two atomsshared between two atoms

Covalent BondsCovalent Bonds

Covalent BondingCovalent Bonding22

There are no ions involved with There are no ions involved with covalent bonds which means no covalent bonds which means no charges.charges.

This is a bond between two This is a bond between two nonmetals.nonmetals.

Electrons are Electrons are shared.shared. The magic number is still 8.The magic number is still 8.

Covalent propertiesCovalent properties

covalent bonds are weaker than ionic bondscovalent bonds are weaker than ionic bonds they are poor conductors of electricitythey are poor conductors of electricity They have low melting points and boiling They have low melting points and boiling

pointspoints They are usually very dull in appearanceThey are usually very dull in appearance

Covalent NomenclatureCovalent Nomenclature

When naming covalent compounds, you When naming covalent compounds, you MUST use prefixes for the first and second MUST use prefixes for the first and second wordswords

The only exception is if you only have one The only exception is if you only have one atom for the first element.atom for the first element.

the less electronegative (furthest to the left the less electronegative (furthest to the left on the p/t) element is given first and its full on the p/t) element is given first and its full element name is writtenelement name is written

-ide is still needed at the end of the -ide is still needed at the end of the secondsecond element as well as a prefixelement as well as a prefix

Covalent molecule Covalent molecule prefixesprefixes

1.1. Mono-Mono-2.2. Di-Di-3.3. Tri-Tri-4.4. Tetra-Tetra-5.5. Penta-Penta-6.6. Hexa-Hexa-7.7. Hepta-Hepta-8.8. Octa-Octa-9.9. Nona-Nona-10.10. Deca-Deca-

Covalent nomenclatureCovalent nomenclature

ExamplesExamples Dihydrogen monoxide (HDihydrogen monoxide (H22O)O)

Sulfur trioxide (SOSulfur trioxide (SO33)*there is only one sulfur )*there is only one sulfur

so no prefix is needed.so no prefix is needed. Trisilicon tetranitride (SiTrisilicon tetranitride (Si33NN44))

Dinitrogen Pentaoxide (NDinitrogen Pentaoxide (N22OO55))