Notes 6 - Ions & Notes 6 - Ions & Chemical BondingChemical Bonding

Unstable AtomsUnstable Atoms► In order to be stable, an atom needs a In order to be stable, an atom needs a

certain number of valence electronscertain number of valence electrons 2 valence e2 valence e-- if it only has 1 energy if it only has 1 energy

levellevel 8 valence e8 valence e-- if it has 2+ energy levels if it has 2+ energy levels

►Most atoms are unstableMost atoms are unstable► In order to become stable, atoms may:In order to become stable, atoms may:

take electrons from other atomstake electrons from other atoms lose electrons to other atomslose electrons to other atoms share electronsshare electrons

► To determine if an atom is To determine if an atom is stablestable or or unstableunstable, you must look at the number of , you must look at the number of valence electrons.valence electrons.

NeonNeon

Example: Neon has 8 electrons in the last Example: Neon has 8 electrons in the last level, so it is level, so it is stablestable

CarbonCarbon Hydrogen Hydrogen

►Carbon has 4 electrons in the last Carbon has 4 electrons in the last

level, so it is level, so it is unstableunstable►Hydrogen has 1 electron in the last Hydrogen has 1 electron in the last

level, so it is level, so it is unstableunstable as well as well

The Noble GasesThe Noble Gases►Group 8 elements all Group 8 elements all

have 8 valence have 8 valence electronselectrons

►They are naturally They are naturally stablestable

►They do not give, take, They do not give, take, or share electronsor share electrons

►They don’t react or They don’t react or form bonds with other form bonds with other atomsatoms

Ion FormationIon Formation►IonIon – an atom that gains or loses one – an atom that gains or loses one

or more electronsor more electrons► Ions form so that atoms can become Ions form so that atoms can become

stablestable►Atoms with a valence of 3 or less will Atoms with a valence of 3 or less will

lose electronslose electrons►Atoms with a valence of 5 to 7 will Atoms with a valence of 5 to 7 will

take electronstake electrons►When atoms lose or take electrons, When atoms lose or take electrons,

they become chargedthey become charged

Why do ions have a Why do ions have a charge?charge?►Atoms that have lost or gained Atoms that have lost or gained

electrons have unequal numbers of electrons have unequal numbers of protons and electronsprotons and electrons

►Atoms that gain electrons have more Atoms that gain electrons have more electrons (e-) than protons (p+), so electrons (e-) than protons (p+), so they become negative ionsthey become negative ions

►Atoms that lose electrons have more Atoms that lose electrons have more protons (p+) than electrons (e-), so protons (p+) than electrons (e-), so they become positive ionsthey become positive ions

Examples of IonsExamples of IonsNaNa++ Li Li++ Ca Ca2+2+ Fe Fe2+2+ AlAl3+3+

ClCl-- F F-- O O2-2- S S2-2- N N3-3-

Metals vs Non-metalsMetals vs Non-metals ► Metals are unstableMetals are unstable► Metals have valences of Metals have valences of

1, 2, or 31, 2, or 3► Metals give up valence Metals give up valence

electrons and become electrons and become positive ionspositive ions

► EX. LithiumEX. Lithium Valence of 1Valence of 1 Loses 1 electronLoses 1 electron Becomes a positive ion Becomes a positive ion

(Li(Li++))

Metals vs Non-metalsMetals vs Non-metals

►What is a magnesium atom’s valence?What is a magnesium atom’s valence? 2 (It is in Group 2 – that is how you know)2 (It is in Group 2 – that is how you know)

►So how many electrons would it give So how many electrons would it give up to become stable?up to become stable? 22

►What is a sodium atom’s valence?What is a sodium atom’s valence? 11

►So how many would it give up?So how many would it give up? 11

Metals vs Non-metalsMetals vs Non-metals ► Non-metals are unstable Non-metals are unstable

except for the noble except for the noble gasesgases

► Non-metals have Non-metals have valences of 4, 5, 6, or 7valences of 4, 5, 6, or 7

► Non-metals take valence Non-metals take valence electrons and become electrons and become negative ionsnegative ions

► EX. ChlorineEX. Chlorine Valence of 7Valence of 7 Gains 1 electron Gains 1 electron Becomes a negative ion Becomes a negative ion

(Cl(Cl--))

Metals vs Non-metalsMetals vs Non-metals►What is an oxygen atom’s valence?What is an oxygen atom’s valence?

6 6 ►How many electrons would it need to How many electrons would it need to

take to become stable?take to become stable? 22

►What is a fluorine atom’s valence?What is a fluorine atom’s valence? 77

►How many would it need to take?How many would it need to take? 11

Chemical BondingChemical Bonding

►Chemical bondingChemical bonding – when 2 or more – when 2 or more unstable atoms stick together in order unstable atoms stick together in order to become stableto become stable

►Chemical bondChemical bond – an attractive force – an attractive force that holds atoms togetherthat holds atoms together

►Atoms may bond together by:Atoms may bond together by: opposite ions attracting opposite ions attracting

(positive(positivenegative)negative) sharing electronssharing electrons

Chemical BondingChemical Bonding

► There are 3 types of chemical bonds:There are 3 types of chemical bonds:

1.1. Ionic bondsIonic bonds

2.2. Covalent bondsCovalent bonds

3.3. Metallic bondsMetallic bonds

Ionic Bonds – What are Ionic Bonds – What are they?they?►Ionic bondIonic bond – a bond formed by the – a bond formed by the

attraction between positive and attraction between positive and negative ionsnegative ions

► Ionic bonds form between metal atoms Ionic bonds form between metal atoms and non-metal atomsand non-metal atoms Metal atom forms the positive ion (gives Metal atom forms the positive ion (gives

ee--)) Non-metal atom forms the negative ion Non-metal atom forms the negative ion

(takes e(takes e--))

Ionic Bonds – Ionic Bonds – How do they How do they form?form?► A non-metal atom with more A non-metal atom with more

than 4 valence electrons than 4 valence electrons takes electrons from a metal takes electrons from a metal atomatom

► The non-metal atom The non-metal atom becomes a negative ionbecomes a negative ion

► The metal atom becomes a The metal atom becomes a positive ionpositive ion

► The opposite ions attract The opposite ions attract forming an forming an ionic bondionic bond

► Ionic compounds are Ionic compounds are generally solids with high generally solids with high melting points (Ex. NaCl – melting points (Ex. NaCl – Salt)Salt)

More Atom HumorMore Atom Humor

Covalent Bonds – What are Covalent Bonds – What are they?they?

►Covalent bondCovalent bond – A bond formed when – A bond formed when atoms share one or more pairs of valence atoms share one or more pairs of valence electrons in order to become stableelectrons in order to become stable EX. HEX. H22O O

►Atoms that share more than one pair of Atoms that share more than one pair of electrons may form double or triple bondselectrons may form double or triple bonds EX. OEX. O22

►Covalent bonds form between atoms of Covalent bonds form between atoms of non-metalsnon-metals

►Metallic BondsMetallic Bonds – bond formed between – bond formed between metal atomsmetal atoms

►Electrons can move between atomsElectrons can move between atoms►Form between atoms of the same elementForm between atoms of the same element►2 different metals can’t bond to each 2 different metals can’t bond to each

otherother Ex. Iron atoms can bond to iron atoms Ex. Iron atoms can bond to iron atoms

metallically, but copper atoms can’t bond to metallically, but copper atoms can’t bond to iron atomsiron atoms

Metallic Bonds – What are Metallic Bonds – What are they?they?

Remember…Remember…

►Unstable atoms form bonds to become Unstable atoms form bonds to become stablestable

►Unstable atoms give, take, or share Unstable atoms give, take, or share electronselectrons

►The Octet Rule – “I’ve got 8, so I’m The Octet Rule – “I’ve got 8, so I’m straight”straight” Atoms with 8 valence electrons are stableAtoms with 8 valence electrons are stable