Chapter 6 Chemical Bonds Ionic Bonding. What we need to Learn How do elements obtain a stable electron configuration? How do types of bonds affect the

Chapter 6Chapter 6Chemical BondsChemical Bonds


Ionic BondingIonic Bonding

What we need to Learn• How do elements obtain a stable

electron configuration?• How do types of bonds affect the

properties of different substances?

Bell Ringer Tuesday

1. Describe the structure of atoms. An atom consists of a dense, positively

charged nucleus with protons and neutrons, surrounded by space where negatively charged electrons moveTrue or False: Objects with opposite charges attract one another. True

3.What are valence electrons? Electrons in the highest occupied energy level of an atom

Chapter 6

Bell Ringer Wednesday1. 4. Which group in the periodic table contains elements that

hardly react at all? The noble gases2. Where on the periodic table are nonmetals generally found?

Right side3. How do the compositions of mixtures differ from those of

substances? The composition of a mixture can vary, and the composition of

a substance is fixed

Chapter 6

Words to know• For homework write your own

definition for the following words and illustrate each word.

• Due Tuesday– Electron dot diagram, Ion, Anion,

Cation, Chemical Bond, Ionic Bond, Chemical Formula, crystals (Pg 158)

– Ex: Electron dot diagram (do together)

Quick Lab Activity• What Can the shape of a material

tell you about the material?• Think About it

– Sodium Chloride (NaCl) are cubes. – Alum crystals are ‘cuboids’ – shaped

like a cube that is missing part of a side.

– Epsom salts look like cylinders with one or both ends pointed.

– Sucrose crystals may appear oblong with slightly slanted ends.

6.1 What you need to know from this chapter!

• Recognize stable electron configurations• Use number of valence electrons and dot

diagrams to predict chemical properties• Describe how an ionic bond forms and

how ionization energy is related• Predict the composition of an ionic

compound from it’s chemical formula• Relate properties of ionic compounds to

crystal lattice structure

• When is an atom unlikely to react (most stable)?

Stable Electron Configurations

•When the highest occupied energy level of an atom is filled with electrons, the atom is stable and not likely to react.•What do the chemical properties of an element depend on?

• The chemical properties of an element depends on the number of valence electrons.

• An electron dot diagram (aka Lewis Dot) is a model of an atom in which each dot represents a valence electron. –(see P. 159, fig 2)

• The symbol in the center represents the nucleus and all the other electrons in the atom.


• Noble gases are the most stable elements.

• The highest occupied energy level of a noble gas atom is completely filled.

• The noble gases have stable electron configurations with eight valence electrons (two electrons in the case of helium).

–Elements tend to react to achieve electron configurations similar to those of noble gases.

–How do you think they get these configurations?


What is one way in which elements can achieve stable electron configurations?

Ionic Bonds

Some elements achieve stable electron configurations through the transfer of electrons between atoms.Look at page 159 again at Cl and NaDraw the atoms before and after the transfer

How might the atom change when it gains or loses electrons?

Formation of Ions• When an atom gains or loses an electron,

the number of protons is no longer equal to the number of electrons.

• The charge on the atom is not balanced, and the atom is not neutral.

•An atom that has a net positive or negative electric charge is called an ion.

•The charge on an ion is represented by a plus or a minus sign.

Ionic Bonds

The ion that forms when a chlorine atom gains an electron has 17 protons (+) and 18 electrons(-). • This ion has a NET charge of 1–.• The symbol for the ion is written Cl1–, or Cl– for

short.

•An ion with a negative charge is an anion.

• Anions like the Cl– ion are named by using part of the element name plus the suffix –ide. Thus,

Cl– is called a chloride ion.

Ionic Bonds

A sodium ion has 11 protons and 10 electrons.• The sodium ion has a charge of 1+. • The symbol for the ion is written Na1+, or Na+

for short.

•An ion with a positive charge is a cation.

• A cation uses the element name, as in the sodium ion.

Ionic Bonds

Practice

• Get out your periodic table and complete the chart for naming ions.

Symbol Type of Ion Name of Ion

S2- Anion Sulfide Ion

Li1+

F1-

O2-

K1+

Mg2+

Ionic Bonds

Formation of IonsScientists use atomic radii to compare the

sizes of atoms of different elements. The radius of a sphere is the distance from the center of the sphere to its outer edge–half the diameter of the sphere.

Remember:

+ and – attract!

Radii is plural for

radius

Radii is plural for

radius

Formation of Ionic BondsA particle with a negative charge will attract

a particle with a positive charge.

•A chemical bond is the force that holds atoms or ions together as a

unit. •An ionic bond is the force that

holds cations and anions together. An ionic bond forms when

electrons are transferred from one atom to another.

Ionic Bonds

Ionization EnergyCations form when electrons gain enough

energy to escape from atoms. The energy allows electrons to overcome the attraction of the protons in the nucleus.

The amount of energy used to remove an electron is called ionization energy.

The lower the ionization energy, the easier it is to remove an electron from an atom.

Ionic Bonds

Ionization energies increase from left to right across a period.

Ionic Bonds

It takes more energy to remove an electron from a nonmetal than from a metal in the same period.It takes more energy to remove an electron from a nonmetal than from a metal in the same period.

How does the structure of an ionic compound affect its properties?

Solids whose particles are arranged in a lattice structure are called crystals.

Ionic Compounds

The properties of an ionic compound can be explained by the strong attractions among ions within a crystal lattice.

Compounds that contain ionic bonds are ionic compounds, which can be represented by chemical formulas.

•A chemical formula is a notation that shows what elements a compound contains and the ratio of the atoms or ions of those elements in the compound.

Ionic Compounds

What is the chemical formula for magnesium chloride?Look at page 161

Draw the lewis dot structure for Magnesium Chloride

How can you tell what the formula is for Magnesium chloride from this diagram?

Ionic Compounds

The arrangement of particles in a substance is the result of two opposing factors: the attractions among particles in the substance and the kinetic energy of the particles.• The stronger the attractions among the

particles, the more kinetic energy the particles must have before they can separate.

• Ions in a solid crystal lattice have fixed positions, when the solid melts, what happens to the ions?

• they move from their positions and flow

• Ionic compounds have strong attractions between particles and therefore, high melting points.

Ionic Compounds

For an electric current to flow, charged particles must be able to move from one location to another.• Ions in a solid crystal lattice have fixed

positions. Solid sodium chloride is a poor conductor of electric current.

• When the solid melts, the lattice breaks apart, and the ions are free to flow. Molten sodium chloride is an excellent conductor of electric current.

Ionic Compounds

When an ionic crystal is struck, ions are moved from their fixed positions.

negative ions are pushed near negative ions and + near +

Ions with the same charge repel one another and the crystal shatters.

Ionic Compounds Hammer strikes crystal

Ionic crystal shatters when struck.

Assessment Questions1. When is an atom stable?

a. when its electrons are evenly distributed through its energy levels

b. when its lowest occupied energy level is filled with electrons

c. when its highest unoccupied energy level is filled with electrons

1. when its highest occupied energy level is filled with electrons

Assessment Questions

Do section 6.1 assessment.Workbook 6.1 for homework



6.2 Covalent 6.2 Covalent BondingBonding

Covalent Bonds

• How are atoms held together in a covalent bond? The attractions between the shared electrons and the protons in each nucleus hold the atoms together in a covalent bond.

• A covalent bond is a chemical bond in which two atoms share a pair of valence electrons.

Sharing Electrons• A hydrogen atom has one electron. If it

had two electrons, it would have the same electron configuration as a helium atom.

• Two hydrogen atoms can achieve a stable electron configuration by sharing their electrons and forming a covalent bond.–When two atoms share one pair of electrons, the bond is called a single bond.

Covalent Bonds

• Ionic Compounds• Crystalline solids (made of ions)• High melting and boiling points• Conduct electricity when melted• Many soluble in water but not in nonpolar liquid

• Covalent Compounds

• Gases, liquids, or solids (made of molecules)• Low melting and boiling points• Poor electrical conductors in all phases• Many soluble in nonpolar liquids but not in water

Ionic Vs. Covalent Bond

Ionic Bond

Covalent Bond

Molecules of Elements

• A molecule is a neutral group of atoms that are joined together by one or more covalent bonds.

• Neutral means the + and – protons and electrons equal out.

• In a covalent bond, two nonmetals (friends) SHARE electrons

Covalent Bonds

• Some nonmetal elements exist as diatomic molecules

• Diatomic means “two atoms.”

• Oxygen is also diatomic (O2)

Covalent Bonds

Multiple Covalent Bonds• When two atoms share two pairs of

electrons, the bond is called a double bond.

• When two atoms share three pairs of electrons, the bond is called a triple bond.

• Nitrogen has five valence electrons. When the atoms in a nitrogen molecule (N2) share three pairs of electrons, each atom has eight valence electrons.

Each pair of shared electrons is represented by a long dash

in the structural formula NN.

Covalent Bonds

• Except for noble gases, elements on the right of the periodic table tend to have a greater attraction for electrons than elements on the left.

• Elements at the top of a group tend to have a greater attraction for electrons than elements at the bottom of a group have.

• Fluorine is on the far right and top of the group – it has the strongest attractions for electrons and is therefore the most reactive

metal.

Unequal Sharing of Electrons

Polar Covalent Bonds• Friends don’t always share equally do

they?• When electrons are not shared

equally in a covalent bond it is called polar covalent –One atom is greedier than the other!

• In a non-polar covalent bond, electrons are shared equally.


• Polar molecules have stronger attractions than nonpolar.

• A covalent compound forms when hydrogen reacts with chlorine.• A chlorine atom has a greater attraction for

electrons than a hydrogen atom does. • In a hydrogen chloride molecule, the shared

electrons spend more time near the chlorine atom than near the hydrogen atom.


In a carbon dioxide (CO2) molecule, the polar bonds between the carbon atom and the oxygen atoms cancel out because the molecule is linear.

In a water (H2O) molecule,

the polar bonds between the oxygen atom and the hydrogen atoms do not cancel out because the molecule is bent.


Predicting Bond Types• A metal and nonmetal will form

ionic bonds• Compounds between nonmetals

will be covalent



6.4 The 6.4 The Structure of Structure of

MetalsMetals

Review• Ionic Bonds are formed between a

metal and a nonmetal. • Covalent Bonds are formed

between two non-metals. • We also have Hydrogen bonding

Hydrogen Bonds• Hydrogen atoms are attracted to

an element that attracts electrons (oxygen) on a nearby molecule

• These types of bonds are called hydrogen bonds .

Polar molecul

e

Polar molecul

e

Bonding Review• Ionic and Covalent bonds are

bonds between ions or atoms • Hydrogen bonds are attractions

between molecules• We also have metallic bonds

between atoms in a metal

Structure of Metals

• What are the forces that give a metal its structure as a solid?

• How do metallic bonds produce some of the typical properties of metals?

Metallic Bond• How do molecules of metal hold

together? – Metal atoms can lose or gain electrons

to become stable. – Metal atoms become cations

surrounded by a pool of shared electrons

• A metallic bond is made by the sharing of electrons between a metal cation and the electrons that surround it.

Metallic Bonds• The cations form a lattice

structure (pg 177 fig 22)– the total number of electrons does

not change. • Valence electrons are just able to move

and be shared

– The more valence electrons an atom shares, the stronger the metallic bond will be.

Explaining Explaining Properties of Properties of

MetalsMetals

Explaining Explaining Properties of Properties of

MetalsMetals

How does the structure within a How does the structure within a metal affect it’s properties?metal affect it’s properties?

Properties of Metals– The strength (or weakness) of the

bond relates to the metal’s properties– which is directly related to # of valence

electrons

• Metals with weak bonds (like alkali metals) such as Sodium (Na) are soft enough to cut with a knife and have a low melting point

• Transition metals like Tungsten have more valence electrons and are therefore harder and have higher melting points.

Properties of Metals• What are some of the properties

of metals?– An electric current is a flow of

charged particles– Where do these charged particles

come from?• Electrons! An electric current can be

carried through a metal by the free flow of the shared electrons.

Properties of Metals• Fig 22 • Cations are surround

by shared valence electrons

• The ions shift their position and the metal changes shape

• It does not shatter because the ions are held together by the metallic bonds

How are the properties of alloys controlled?

Alloys

Scientists can design alloys with specific properties by varying the types and amounts of elements in an alloy.

•An alloy is a mixture of two or more elements, at least one of which is a metal.

•Alloys have the characteristic properties of metals.


1. What force holds the atoms of a metal together? a. the attraction of a positively charged

atom to a negatively charged atomb. the sharing of electrons between two

atomsc. the gravitational force between dense

metal atoms1. the attraction between metal cations and

a pool of shared electrons

Assessment Questions2. Why are solid metals good conductors of

electric current?a. Metals are good conductors because they

can be drawn into wires.b. Metals are good conductors because they

are solids at room temperature.c. The nuclei of metal atoms can move

easily because they repel one another.2. Shared electrons are able to flow freely

through the metal.

Metallic Questions3. How does metallic bonding

account for the properties of metals?

4. Outline the section on Alloys



6.3 Naming 6.3 Naming Compound and Compound and

Writing FormulasWriting Formulas

Naming Compounds• How did we get last names?• Chemical names for compounds

are based on composition (what it’s made of) and how many atoms of each type of element is in the compound

• When would the composition of a chemical be important to know?– Medication, fertilizer, recipes,

perfume, pesticide, make up

Describing Ionic Compounds

• Look at Pg 171 Fig 15 – how can you be sure that these oxides of copper are from different compounds?

• Both are made from copper and Oxygen– CuO and Cu2O

• There must be at least 2 names to distinguish between the red copper oxide and the black copper oxide.

Naming• Just like last names used to

describe something about a person, the name and formula of a compound describe the type and number of atoms in a compound.

Binary Ionic Compounds

• A compound made from only two elements is a binary compound.

• The names have a predictable pattern: the name of the cation followed by the name of the anion. (ex: NaCl Sodium Chloride)

• Remember the Cation or “boy” keeps his hame (and is first) and the Anion or “girl” changes her ‘last’ name to –ide.

»Ex: Iodine atom becomes iodide ion or sodium iodide if a compound.


Metals with Multiple Ions

• Many metals are ‘faithful’ and only form one ion. K+ Ca2+ Al3+

• Many of the transition metals, however, ‘play the field’ – they can form more than one type of ion.– Ex: Copper has two ions:

• Copper (I) - with a 1+ charge• Copper (II) – with a 2+ charge• This is how we know the difference

between the red or black copper oxides. (CuO and Cu2O) ex on board

• A covalently bonded group of atoms that has a positive or negative charge and acts as a unit is a polyatomic ion.

Most simple polyatomic ions are anions, but work together as a ‘team’.


‘Poly’ means many

‘Poly’ means many

Modeling QuickLab• make an ammonia

molecule model (NH3)

• NH3 is like a pyramid with Nitrogen at the top and hydrogen atoms at the corners of the base.

• Now make a methane molecule, CH4

• Hydrogen atoms are equally spaced around the carbon

• This molecule is a tetrahedral model

Compare the shapes of the methane and ammonia molecules.Why is carbon in the center of the methane molecule?Compare the shapes of the methane and ammonia molecules.Why is carbon in the center of the methane molecule?

Writing Formulas• The names of some compounds contain clues

about their chemical formulas. • Look at the names of the compounds below.

Try to write a formula for each compound based on what you can figure out from its name and what you know about the elements the compound contains.

• Explain how you determined each formula. 1.sulfur trioxide _____________ 2.magnesium bromide __________ 3.iron(II) chloride ____________

Section 6.3

Writing Formulas for Ionic Compounds• Use the name of an ionic compound to

write its formula. ( metal + nonmetal)– The symbol of the cation is first, followed by

the symbol of the anion.

• Use subscripts to show the ratio of the ions in the compound.

• Parentheses are used with the subscript for polyatomic ions.

• The formula for iron(III) hydroxide is Fe(OH)3. – Draw on board – look at fig 19 pg 173


• Because all compounds are neutral, the total charges on the cations and anions must add up to zero.

• To name an ionic compound (metal and nonmetal or polyatomic ion use this formula:

»Symbol and charge»Cris-cross»Reduce


Writing Formulas for Ionic Compounds

What is the formula for the ionic compound calcium chloride?


1. Write the formula for the compound calcium oxide.


2. Write the formula for the compound copper(I) sulfide.


3. Write the formula for the compound sodium sulfate.


4. What is the name of the compound whose formula is NaOH?


Naming Molecular Compounds• The the most metallic element appears first

in the name. – These elements are farther to the left in the

periodic table. – If both elements are in the same group, the

more metallic element is closer to the bottom of the group.

• The name of the second element is changed to end in the suffix -ide, as in carbon dioxide.

Describing Molecular Compounds

• There may be more than one molecular compound that can exist with the same two elements.

• The Greek prefixes in the table are used to name molecular compounds.

• These are used when you have two non-metals


• Two compounds that contain nitrogen and oxygen have the formulas N2O4 and NO2.

• Use the prefixes to name them


Writing Molecular FormulasTo write the formula for a molecular

compound, write the symbols for the elements in the order the elements appear in the name.• The prefixes indicate the number of

atoms of each element in the molecule. • The prefixes appear as subscripts in the

formulas. • If there is no prefix for an element in the

name, there is only one atom of that element in the molecule.


What is the formula for diphosphorus tetrafluoride?



1. Which of these formulas describes a binary ionic compound? a. O2

b. MgCl2c. NO2

1. Fe(OH)3


2. What is the correct name for CCl4? a. carbon(IV) chlorideb. carbon tetrachlorinec. carbon tetrachloride2. monocarbon tetrachloride

Math practice

• What are the names of these ionic compounds: LiCl, BaO, Na3N and PbSO4

• Name the compounds with these formulas: P2O5 and CO.

• What is the formula for the ionic compound formed from potassium and sulfur?

Documents

Chapter 6 Chemical Bonds Ionic Bonding. What we need to Learn How do elements obtain a stable electron configuration? How do types of bonds affect the