Section 3 - Bonding Flashcards
What is Ionic Bonding?
Bonding that occurs between Metals and Non-Metals, when ions are held together by electrostatic attraction.
How are ions formed?
When one or more electrons are transferred from one atom to another.
Do metals lose or gain electrons when they become ions?
They lose them.
Do non-metals lose or gain electrons when they become ions?
They gain them.
What is the formula for a sulfate ion?
SO₄²⁻
What is the formula for a hydroxide ion?
OH⁻
What is the formula for a nitrate ion?
NO₃⁻
What is the formula for a carbonate ion?
CO₃²⁻
What is the formula for a ammonium ion?
NH₄⁺
What is the structure of an ionic bond?
A giant ionic lattice.
What is the melting point of ionic bonds?
High - lots of strong forces of attraction between +ive and -ive ions.
Are ionic lattices good conductors of electricity?
Yes.
How do you make a giant ionic lattice conduct electricity?
Make the ions move by heating it up or dissolving it if it can be dissolved.
Why do giant ionic lattices need to be molten or dissolved to conduct electricity?
In a solid the ions are fixed by strong ionic bonds.
They need to be free to move and carry a charge.
Do ionic compounds dissolve in water?
Generally yes - water molecules are polar and the charged parts on them pull ions away from the lattice.
What is the order of mpts in LiCl, LiBr and LiF? And why?
Because LiF is the smallest so has the strongest FoA.
How many Cl- ions is each Na+ bonded to?
6
What is Covalent Bonding?
Bonding that occurs between non-metals, when two or more atoms share a pair of electrons.
What is a co-ordinate/dative covalent bond?
A shared pair of electrons provided by one atom.
What are the two types of covalent bonds?
Molecular and Giant Covalent.
What are giant covalent structures?
Huge networks of covalently bonded atoms.
What is the structure of graphite?
- Each carbon is covalently bonded to 3 other carbons.
- The 4th outer electron of each carbon is delocalised.
What are the properties of graphite?
- Soft and brittle - layers slide.
- Conducts electricity - free electrons.
- Low density - layers are far apart.
- Very high mpt - very strong covalent bonds.
- Insoluble - covalent bonds are too strong to break.
What is the shape of graphite?
- Hexagonal planar sheets of bonded carbons.
- Delocalised electrons and Van der Waals between layers.
What is the structure of Diamond?
- Each carbon is bonded to 4 other carbons.
- Not layered.
What are the properties of diamond?
- Doesn’t conduct electricity - no free electrons.
- Insoluble - covalent bonds are too strong to break.
- Very high mpt - very strong covalent bonds.
- Extremely hard.
What is the shape of diamond?
It is arranged in a tetrahedral shape.
What is the structure of Iodine?
It is molecular.
Pairs of iodine atoms are covalently bonded and held together by weak intermolecular forces.
What is Iodine’s mpt/bpt?
Low - only need to overcome weak IMFs.
What is the structure of Ice?
It is molecular - H2O molecules are held together by IMFs between Hs and Os.
What is the shape of a molecule/ion with 2 bonding pairs of electrons? And what is the bond angle?
Linear. 180.
What is the shape of a molecule/ion with 3 bonding pairs of electrons? And what is the bond angle?
Trigonal Planar. 120.
What is the shape of a molecule/ion with 2 bonding pairs and 1 lone pair of electrons? And what is the bond angle?
Bent. 117.5.
What is the shape of a molecule/ion with 4 bonding pairs of electrons? And what is the bond angle?
Tetrahedral. 109.5.
What is the shape of a molecule/ion with 3 bonding pairs and 1 lone pair of electrons? And what is the bond angle?
Trigonal Pyramid. 107.
What is the shape of a molecule/ion with 2 bonding pairs and 2 lone pairs of electrons? And what is the bond angle?
Bent. 104.5.
What is the shape of a molecule/ion with 5 bonding pairs of electrons? And what are the 2 bond angles?
Trigonal Bipyramid. 90 and 120.
What is the shape of a molecule/ion with 4 bonding pairs and 1 lone pair of electrons? And what are the 2 bond angles?
Seesaw. 87.5 and 117.5.
What is the shape of a molecule/ion with 3 bonding pairs and 2 lone pairs of electrons? And what is the bond angle?
Trigonal Planar. 120. (lone pairs working in equal and opposite directions cancel each other out)
Or
T-shape. 85.
What is the shape of a molecule/ion with 6 bonding pairs of electrons? And what is the bond angle?
Octahedral. 90.
What is the shape of a molecule/ion with 5 bonding pairs and 1 lone pair of electrons? And what is the bond angle?
Helicopter. 87.5.
What is the shape of a molecule/ion with 4 bonding pairs and 2 lone pairs of electrons? And what is the bond angle?
Square Planar. 90.
What is a good method for working out shapes of molecules?
- Add group number to number of bonds to charge. (a negative charge is a +1 and positive is -1)!!!!
- Divide answer by 2 to get number of pairs.
- Calculate how many bonded pairs and how many lone pairs.
What is the most electronegative element?
Fluorine.
What is the general trend in electronegativity?
Increases across periods.
Decreases down groups.
What is a polar bond?
A bond between two atoms of different electronegativities where the electron pair is pulled closer to the more electronegative atom.
Is H2 polar?
No - it’s non-polar.
Is C-H polar?
No - C and H have practically the same electronegativity.
How are permanent dipoles formed?
In a polar bond, the difference in electronegativity causes a delta positive and a delta negative charge.
What is a polar molecule?
It is a molecule with polar bonds, which causes an uneven distribution of charge across the molecule.
What happens if polar bonds are symmetrical in a molecule?
The molecule will be non-polar - the charges cancel out.
What are the 3 types of IMFs?
1) Van der Waals
2) Permanent dipole-dipole forces
3) Hydrogen Bonding
What are Van der Waal forces?
Instantaneous dipole dipoles.
Define electronegativity
The ability of an atom to attract a pair of electrons in a covalent bond.
When can Hydrogen Bonding occur?
When H is covalently bonded to N O or F.
How is a dipole formed?
When electrons are grouped more on one side of an atom than the other for an instant.
How do Van der Waals forces form?
An instant dipole causes an instant dipole on a neighbouring atom which causes an instant dipole on the next atom, etc. This causes a constant attraction.
Why might a molecule have stronger VdWs and therefore higher mpts?
- Larger molecules = larger electron clouds = stronger VdWs
- Long straight molecules can lie closer together = stronger VdWs
What is the strength order of IMFs?
- Hydrogen Bonding
- Dipole Dipole
- Van der Waals
How does Hydrogen Bonding occur?
- N, O and F are very electronegative
- They draw electrons away from H creating a polar bond.
- H has such a high charge density that the atoms form weak bonds with lone pairs on the N O or F.
What is the structure of metallic bonding?
- Giant Metallic Lattice
- The outer shell of electrons of a metal atom is delocalised.
- There is an attraction between positive metal ions and a sea of delocalised electrons.
What are the properties of a metallic bond?
- High melting point - strong FoA
- The more delocalised electrons, the higher the mpt.
- Good conductors of heat and electricity - electrons can carry a current.
- Soft/malleable - layers can slide.
- Insoluble (except liquid metals) - too strong.
