In your notebook: Bonding What does bonding mean? What types of things do we use to bond items/materials together? Why choose one over the other?

How do we bond things together in the “real world” Bonding What does it mean? How do we bond things together in the “real world”

https://www.youtube.com/watch?v=WcWeUUzOuHk​

Compound Element Atom Molecule A particle containing 2 or more atoms (of the same or different types Compound The simplest type of particle Element A substance made of 2 or more types of atom chemically combined Atom A substance made of only 1 type of atom Molecule

Atoms bond by Sharing electrons – covalent bonds (between non-metals only) Gaining or losing electrons – ionic bonds (between metal and non-metal) Unfixed sharing electrons – metallic bonds (between metals only) All three types involve changes in the electrons in the outermost electron shells of the atoms

Electron shells and bonding Atoms are only “happy” when their outer shell is full They will either lose or gain electrons in order to become “happy” If they lose electrons they become positive ions (the number of protons is bigger than the number of electrons) If they gain electrons they become negative ions (the number of protons is smaller than the number of electrons)

General rule Non-metals usually form negative ions Metals usually form positive ions

What are the two types of bonds? Who are they between… No notes!

Ions in uniform structure Ions moving freely in solution 2. Ionic bonding Made from reaction of metals with non-metals. F- Li F Electron donation Li+ Attraction Positive metal ions and negative non-metal ions attract each other strongly to make potentially infinitely large continuous and uniform structures. + Ions in uniform structure Water Ions moving freely in solution

2. Ionic bonding Ionic compounds’ characteristics: High melting points Hard but brittle Uniform, repeat structure (alternating + & – ions) Unreactive when solid (especially “ordinary” ionic compounds, e.g. NaCl, MgO) Dissolve in water to create solutions Do not conduct electricity when solid, but do in solution or when molten

Ionic bonding E.g. Sodium + Chlorine → Sodium chloride Cl Na Outer shells not full!

Ionic bonding E.g. Sodium + Chlorine → Sodium chloride NaCl (Na+Cl-) Cl Na Copy example Both ions have full outer shells

Beryllium fluoride - BeF2

Beryllium fluoride - BeF2 Each beryllium atom need to loose two electrons, but each fluorine only needs 1 2+ F Copy example Be F

Questions Describe the formation of positive and negative ions Draw dot and cross diagrams for ions of: Potassium and bromine Lithium and chlorine 3. Draw dot and cross for ions of: Calcium and oxygen Beryllium and oxygen

Warm Up!! Show the bonds of PbI2 Show the bonds of AgCl

1. Simple covalent bonding Normally small molecules made from non-metals bonded to non-metals Methane, CH4 Ammonia, NH3 Sulfur dioxide, SO2 But it also applies to relatively large molecules, like proteins and polymers Nylon Small protein molecule

1. Simple covalent bonding Covalently bonded compounds are small and use covalent bonds (share electrons). Low melting points Solids, liquids or gases at room temperature Small, finite structures (although polymers are finite but very long) Can be very reactive due to size and combination of non-metals Normally soft and brittle when solid Volatile (e.g. iodine, I2, evaporates from solid to gas easily at room temperature)

Covalent Bonding Describe the formation of covelant bonds. Draw dot and cross diagrams. Describe the electron arrangement in covelant molecules with 3 or more different types of atoms. Describe the formation of double and triple bonds.

Covalent compounds Covalent compounds are formed when NON-METAL atoms react together. Covalent bonding – bonding in which a pair of electrons, one from each atom, is shared between two atoms.

Covalent bonds Covalent compounds are held together by this sharing of electrons. It is sometimes represented in full bonding diagrams (see figure 1). Often these bonds are just shown as a line (see figure 2). O H - Figure 1 Figure 2 - H

Covalent and electron structures bonding The purpose of covalent bonding is to gain a full outer electron shell. This is achieved by sharing electrons where the shared electrons count towards the outer shells of both atoms. O H Cl C H Water C O Chlorine Carbon dioxide N H Methane Ammonia

Critical Thinking Checkpoint How many atoms of each element are in this compound? Sr3(PO4)2

Covalent bonding in chlorine Chlorine (2,8,7) needs 1 more electron to attain a full electron shell. Cl (2,8,7) Cl (2,8,7) Cl-Cl Cl (2,8,8) Cl (2,8,8)

Hydrogen (1) needs 1 more electron. How many does carbon (2,4) need? 4 How many hydrogen's per 1 carbon? 4 C H C H

Covalent bonding - multiple bonds Mostly electrons are shared as pairs. There are some compounds where they are shared in fours or even sixes. This gives rise to single, double and triple covalent bonds. Again, each pair of electrons is often represented by a single line when doing simple diagrams of molecules. Cl-Cl Single bond O=O Double bond N=N Triple bond

Please Grab A Project Sheet, If 2 fathers and 2 sons go on a fishing trip and each one catches one fish, why do they only bring home 3 fish?

Riddle Me This What starts out on all fours, lives most of its life on two, and dies on three?

Relationship between bond order, strength and length We have learned that covalent bonds can come as either single, double or triple bonds. We also saw in the last section that we identify these different types of bonds by their bond order.

In what way does a bond change as the bond order increases In what way does a bond change as the bond order increases? It turns out that both the length and strength of a bond change with bond order.

Bond # of electrons Bond Order Bond Strength Bond Length Single 2 1 Weakest Longest Double 4   Triple 6 3 Strongest Shortest

One analogy you can use is to think about atoms as nerf balls and bonds as rubber bands. The rubber bands act as the force which holds the balls together, as we increase the number of rubber bands the balls are squished closer together and it takes more force to pull them apart.

In a molecule as you increase the number of electrons shared between two atoms, you increase the bond order, increase the strength of the bond, and decrease the distance between nuclei.

Covalent bonding in oxygen Oxygen (2,8,6) needs 2 more electrons to attain a full electron shell. O X O O=O 4 electrons O X

Three or more atoms present CH3OH - Methanol

Draw a dot and cross diagram for: Chloromethane CH3Cl

Bonding and physical properties Covalent compounds are insoluble in water unlike ionic Covalent compounds don’t conduct electricity in water There are no ions in covalent compounds, unlike ionic compounds. Covalent compounds generally have much lower melting and boiling points than ionic. Interact with each other through ‘weak’ INTERMOLECULAR FORCES H O electrons fixed in covalent bonds

Questions Describe the formation of covelant bonds Draw dot and cross diagrams for hydrogen, water, and hydrogen chloride Describe the electron arrangement in covelant molecules with 3 or more different types of atoms Describe the formation of double and triple bonds

Quiz Which one of the following pairs atoms is most likely to form an ionic bond? A. Na and F B. C and F C. N and F D. O and F

- - - - - - - - Define the following terms: Ionic Structure I know what is meant by a covalent bond. I can draw a diagram to show a covalent bond. I know the properties and characteristics of covalent structures. Keywords: Covalent, Electrons, Molecular, Giant Covalent, Define the following terms: Ionic Structure A substance that is made of ions (where ions are transferred) which are held together by strong attraction. - + - + + - + - - + - + + - + -