Warm-up

• Describe what occurs before and during an ionic bond.

• If the bond is broken what happens to the atoms?

• Describe what occurs before and during a covalent bond.

• If the bond is broken what happens to the atoms?

Quick Tip

• Any slides that appear in this pattern are the slides you need to copy in your notes.

• Any text that is italicized is important and should be written down in your notes.

• All other slides and text do not need to be written down.

• Anything written in red should be written down.

Bonding

Today’s Objectives

• Know what ionic bonding is.• Understand what occurs during ionic bonding.• Interpret the periodic table and predict the

type of ion that will form.

Essential Questions

Explain the processes that allow atoms to combine to form molecules.

Bonding

• Bonding occurs when two or more atoms join together.

• There are three types of bonds (we will only discuss the first two):

1. Ionic- Bond between oppositely charged ions.2. Covalent- Bond when atoms share one or more pairs of

electrons.3. Metallic- bond formed between positively charged metal

ions and the electrons around them.

Ionic Bonding

• What can you tell me about the protons and electrons in an atom?

• What are their charges?• So if I remove an electron or add an electron,

what happens to the atom’s charge?

Ionic Bonding• By removing or adding an electron to an atom an ion

is created.• Ion- an atom or group of atoms that has lost or

gained one or more electron and has a negative or positive charge.

• Atoms like to have complete outer shells, eight electrons on the shell. (Octet rule)

• Knowing this, would it be easier to gain or lose electrons, and why?

Ionic Bonding• Atoms in group 1 are very reactive and as such are very

willing to give up their electron in order to have a complete shell.

• What about the atoms in group 7? Would they gain or give up an electron?

• They are more likely to gain an electron, why?• It’s easier to gain one electron than give up seven.• Atoms of the metal elements, such as sodium and calcium,

form the positive ions. So it is easier to give up an electron.• Atoms of the non-metals, such as chlorine and oxygen, form

the negative charged ions. So it is easier to gain an electron.

Ionic Bonding

• Sodium Chloride is made from sodium and chloride ions.

• What do you think the charge is on the sodium ion? What made you come to your decision?

• How about the chloride ion?

Ionic Bonding

• So we have Na+ and Cl- ions.• What does this all have to do with bonding?• Ionic bonds form between oppositely charged

ions.

Ionic Bonding• Ionic Bonds are formed by the transfer of electrons.• One atom transfers an electron(s) to another atom .• One atom gives an electron(s) and the other atom

takes the electron(s).• This results in a positive ion and a negative ion.• The result of this is the positive ion attracting the

negative ion forming a bond.

Ionic Bonding• These attractions eventually form a network of

bonded ions.• This network then forms crystals, in our NaCl case,

crystals of table salt.• This compound NaCl is made from a positive and

negative ion, resulting in a neutral compound of NaCl.

• One positive Na ion balances one negative Cl ion.• So there is a 1:1 ratio, 1 Na to 1 Cl.

Ionic Bonding

Ionic Bonding Activity

• Take a few minutes to:– Find the oxidation numbers for Calcium and Fluorine.

• Oxidation number– The degree of oxidation of an atom.– For simple atoms the oxidation number is the same

as the ionic charge.– Example:

• Oxidation number for Hydrogen is 1+• Oxidation number for Nitrogen is 3-

Ionic Bonding Activity Solution

• First you have to decide what ions form.• For Calcium is it going to be positive or

negative, what is the value of charge?• For Fluoride will it be positive or negative and

what is the value of the charge?

Ionic Bonding Activity Solution• Calcium is in group 2. How many valence electrons

does it have?• So is it easier to give up or gain ?• This means the Calcium ion’s charge would be

positive or negative?• If it gives up electrons it becomes positive.• So the ion is: Ca2+.

• Calcium gives up 2 electrons allowing the protons to outnumber the remaining electrons by two.

Ionic Bonding Activity Solution• Who wants to give fluorine a chance?• Remember the steps to figure out the ion.

1. Identify Group #2. Determine the # of Valence electrons3. Decide if it is easier to give or receive4. Determine the charge and strength of the ion

• F-.

• Fluorine gains an electron allowing the total number of electrons to outnumber the protons, resulting in a negative charge.

Ionic Bonding Activity Solution• So we now know we have a Ca2+ ion and a F- ion.• How do we get a neutral compound? What is the ratio

we need? In other words how many of each ion do we need to balance the compound?

• You need as many negative charges as you do positive charges.

• So how many positive charges do you have?• There are two positives on the Ca so you need two

negatives to balance them.• So the ratio would be 1:2, or 1 Ca2+ ions for every 2 F-

ions.

Today

• What is ionic bonding?• The transfer of electrons between a metal and

non-metal, creating positive or negative ions.• What happens during ionic bonding?• The positive and negative ions are attracted to

each other forming the bond.

Quick Write

• You are an atom of Barium and are floating around the universe. You come across a group of elements, Neon, Iodine, and Nitrogen. Explain what bonds can be made between the atoms. Then draw the atomic diagram, the ions formed (equation) and the formula of the molecular compound.

Quick Write - Again

• Find your paper (next to the Smart Board) and finish what you began to write last class.

• You are an atom of Barium and are floating around the universe. You come across a group of elements, Neon, Iodine, and Nitrogen. Explain what bonds can be made between the atoms. Then draw the atomic diagram, the ions formed (equation) and the formula of the molecular compound.

Brain Teaser

• Draw the Lewis structures for Hydrogen and Oxygen. What does this tell you about the atom?

Covalent Bonding

Last Time

• We defined ionic bonding.• What is it and what is the process behind it?

Today’s Objectives

• Know what covalent bonding is.• Understand what occurs during a covalent

bond.• Be able to draw a molecule representing a

covalent bond.

Essential Question and Vocabulary

Explain the processes that allow atoms to combine to form molecules.

Vocab:Covalent BondElectron affinityOctet RuleElectron (Lewis) Dot Structure

Covalent Bonding

• So if ionic bonding involves the transfer of electrons, what do you think covalent bonding involves?

• Sharing electrons

Covalent Bonding

Covalent Bonding

• Electron affinity– the power that the positive nucleus of an atom has

to attract the electrons of another atom.• If the affinity is much greater in one atom than

the other then that atom has the ability to steal the electron creating what type of bond?

• An ionic bond.*** Generally an ionic bond is stronger due to their greater electron affinity, however, there are always exceptions to the rule****

Covalent Bonding

• If an atoms electron affinity is not powerful enough to steal the electron then the result is the atoms share the electrons.

• This is what covalent bonding is.• Covalent Bonding – a bond formed when atoms share one or more

pairs of electrons.

Covalent Bonding Example

• Let’s look at Chlorine.• How many valence electrons does it have?• So if one Chlorine atom bonds with another

neither give up an electron. They share one electron to fill there outer shell.

• Octet rule– each atom wants eight electrons on their outer

shell.

Chlorine Covalent Bond

Chlorine Covalent Bond in Electron (Lewis) Dot Structure

Cl Cl

Chlorine Covalent Bond in Electron Dot Structure

• Each atom has eight electrons in its outer shell, so it fulfills the octet rule

• The dots represent electrons not shared.• The line represents the covalent bond where

each atom shares one electron.• The line represents two electrons, one from

each atom.

Covalent Bond Activity

• Spend the next 5 minutes drawing the electron dot diagram for the covalent bond of water.

• Compare with your neighbor.

Covalent Bond Activity Solution

Steps to create the Lewis structure for covalent bond:1. Determine the groups of each atom to see how

many electrons are available to be shared.• Oxygen is in group 6 and has six electrons to

share• Hydrogen is in group 1 and has one electron to

share (but there are two hydrogen atoms)

2. Align the atomic symbols

OH H

Covalent Bond Activity Solution

3. Draw the corresponding dots to represent the unshared electrons and lines to represent the single covalent bond of shared electrons, remembering to obey the octet rule.

OH H

Covalent Bond Activity Solution

Covalent Bonding• The example of the previous slide covalent bond of

water is an example of a single covalent bond.• There can also be multiple covalent bonds or the

sharing of more than two pairs of electrons.• Can you think of any molecule that might be an

example of a double or triple covalent bond?• Double covalent bonds are represented by two lines

instead of a single line. • Triple covalent bonds are represented by three lines.

Question 1

Define covalent bond?

Answer

A covalent bond between two non-metal elements. When the attraction between elements is weak, the result is the elements share electrons rather than transfer electrons.

Question 2

Which is a stronger bond, ionic or covalent? Explain your answer.

Answer

Ionic bonds form stronger bonds because the attraction between the positive and negative particles are greater. The positive protons in the nucleus of one atom have a greater attraction to the negative electrons in another atom, resulting in electron transfer.

Remember there are exceptions to the rule.

Question 3

Draw a covalent bond between Carbon and Hydrogen.

AnswerH

H C H

H

Question 4

Explain why there is only one single line connecting each Hydrogen to the Carbon.

Answer

Lines are used to represent an electron pair in a covalent bond. Since Hydrogen share only a pair of electrons with Carbon, then only one line is needed to represent the bond.

Question 5

Explain what type of bond is formed when an oxygen bonds to an oxygen atom. Draw the Lewis dot structure.

Answer

Since the atoms are two non-metals it is a covalent bond that is formed. When you draw the Lewis dot structure you see that each Oxygen shares a pair of electrons creating a double bond.

Homework

• Research using your books, computers, library, any appropriate resource (including teachers) bring in one example of either a double or triple covalent bond. Complete with the electron dot diagram.

• Also be ready to discuss what polarity means.