Bonding

What does ionic bonding occur between?

Metal and non-metal

What is transferred in ionic bonding?

Metal atoms transfer electrons to non-metals

What is the structure of ionic compounds referred to as?

Lattice structure

What is the strength of ionic bonds affected by?

• The size of the ions

• Charge of the ions

How does size of ions affect ionic bonds?

The smaller the ion they stronger the attraction to the electrons

What state are ionic compounds at room temperature? and why?

• Solid

• They have a giant structure therefore a high melting temperature as the forces require a lot of energy to overcome

In what states do ionic compounds conduct electricity? and why?

• Molten and aqueous

• Ions that carry the current are free to move in the liquid state

Why are ionic compounds brittle?

• They form a lattice of alternating positive and negative ions, a blow may move the ions and produce a contact between like charges

What are molecules?

When two or more atoms bond together

What are the forces like in simple covalent compounds?

• Atoms are held together by covalent bonds

• Molecules are held together by weak intermolecular forces

What is the structure of graphite?

• Carbon atoms are arranged in sheets of flat hexagons covalently bonded with 3 other atoms

• The fourth electron is delocalised

• The sheets are held together by a weak van der Waals force

What are the properties of graphite?

• Weak bonds between the layers mean that it is slippery and can slide over each other

• Delocalised electrons in graphite are free to move along the sheets

• Layers are quite far apart compared to its length of the bond so it has a low density

• High melting point

• Insoluble in any solvent

What is the structure of diamond?

• Each carbon atom has 4 bonds

• They arrange themselves in a tetrahedral shape

What are the properties of diamonds?

• High melting point

• Hard

• Good thermal conductor as particles allow vibrations to pass through

• Can’t conduct electricity

• Won’t dissolve in any solvent

What is dative bonding?

• This is where one of the atoms provides both of the shared electrons

• This occurs when an atom has a lone pair of electrons and the other has none to share

What is valence shell electron pair repulsion theory?

• Electron pairs repel each other

• This results in each pair of electrons being at positions at the greatest possible distance from each other

What does each line represent?

• Full line represents bond in no direction

• Wedge represents bond pointing towards you

• Many lines represents bond pointing away from you

How do you find the number of electron pairs?

1. Find the central atom

2. Work out how many electrons are in the outer shell

3. Add 1 electron for every atom that the central atom is bonded to (take ions into account)

4. Add up the electrons, Divide by 2

5. Compare the number of electron pairs to the number of bonds to find lone pairs

Name the structure, how many electron pairs it has, how many bond pairs ,lone pairs it has and its bond angle

• Linear

• 2 electron pairs

• 2 bond pairs

• 0 lone pairs

• 180 bond angle

Name the structure, how many electron pairs it has, how many bond pairs ,lone pairs it has and its bond angle

• Trigonal planar

• 3 electron pairs

• 3 bond pairs

• 0 lone pairs

• 120 bond angle

Name the structure, how many electron pairs it has, how many bond pairs ,lone pairs it has and its bond angle

• Tetrahedral

• 4 electron pairs

• 4 bond pairs

• 0 lone pairs

• 109.5 bond angle

Name the structure, how many electron pairs it has, how many bond pairs ,lone pairs it has and its bond angle

• Trigonal pyramidal

• 4 electron pairs

• 3 bond pairs

• 1 lone pair

• 107 bond angle

Name the structure, how many electron pairs it has, how many bond pairs ,lone pairs it has and its bond angle

• Bent (V-shape)

• 4 electron pairs

• 2 bond pairs

• 2 lone pairs

• 104.5 bond angle

Name the structure, how many electron pairs it has, how many bond pairs ,lone pairs it has and its bond angle

• Trigonal Bipyramidal

• 5 electron pairs

• 5 bond pairs

• 0 lone pairs

• 120/90 bond angles

Name the structure, how many electron pairs it has, how many bond pairs ,lone pairs it has and its bond angle

• Seesaw

• 5 electron pairs

• 4 bond pairs

• 1 lone pair

• 86/102 bond angles

Name the structure, how many electron pairs it has, how many bond pairs ,lone pairs it has and its bond angle

• T-shape

• 5 electron pairs

• 3 bond pairs

• 2 lone pairs

• 90 bond angles

Name the structure, how many electron pairs it has, how many bond pairs ,lone pairs it has and its bond angle

• Octahedral

• 6 electron pairs

• 6 bond pairs

• 0 lone pairs

• 90 bond angles

Name the structure, how many electron pairs it has, how many bond pairs ,lone pairs it has and its bond angle

• Square pyramidal

• 6 electron pairs

• 5 bond pairs

• 1 lone pair

• 90 bond angles

Name the structure, how many electron pairs it has, how many bond pairs ,lone pairs it has and its bond angle

• Square planar

• 6 electron pairs

• 4 bond pairs

• 2 lone pairs

• 90 bond angles

What is electronegativity?

The power of an atom to attract the electrons in a covalent bond

What are the most electronegative elements?

F, O, N, Cl

What is the pauling scale?

A higher number means an element is better able to attract bonding electrons

When do non-polar covalent bonds form and what does this mean about the shared electrons?

• When atoms have equal number of electronegativity

• Or when both aren’t very electronegative

• This means that the electrons are shared equally

• An example is F2

When do polar covalent bonds form and what does this mean about the shared electrons?

• When one atom is more electronegative than another

• Electrons shared will be closer to the more electronegative one

• An example is H2O

What is a dipole?

It is a difference in charge between two atoms caused by a shift in electrons density in the bond

What is a polar molecule?

If charge is distributed unevenly over a whole molecule then the molecule will have a permanent dipole

	Non-polar molecules	Non-polar molecules	Polar molecules
Description	No polar bonds	Contains polar bonds but all dipoles cancel out	Contains polar bonds but all the dipole moments do not cancel out
Example	CH4	CO2	H2O

What is a van der Waals’ force?

• Causes all atoms and molecules to be attracted to each other

• Electrons in charge clouds are always moving quickly

• These move and and cause temporary dipoles

• These are attracted to each other

• Dipoles destroy and create themselves all the time, but the overall effect is the same

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  • larger molecules have larger electrons clouds which mean they have stronger van de Waals

  • Branched molecules are weaker

What are permanent dipole-dipole forces?

• In molecules that have permanent dipoles, there will be weak electrostatic forces of attraction between the δ+ and δ- charges on neighbouring molecules

What is hydrogen bonding?

• Strongest intermolecular forces

• It only happens when hydrogen is covalently bonded to F, N or O

• The bond is polarised, and hydrogen has such a high chance density that the hydrogen atoms form weak bonds with lone pairs of electrons

What is the behaviour of simple covalent compounds?

• They don’t conduct electricity

• Low melting points

• Can dissolve in water depending on low polarised they are

What are the trends in melting and boiling points?

• As you go down group 7 hydrides, two factors complete

  • Polarity of the molecule

  • Number of electrons

• General trend is that it increases

What is metallic bonding?

• The outermost electrons of a metal atom becomes delocalised

• This leaves a positive metal ion surrounded by a sea of delocalised electrons

• These exist as giant metallic lattice structures

What are the properties of metallic compounds?

• Metals have high melting points

• They are malleable

• They are ductile

• They can conduct electricity

• They are mostly insoluble