Bonding - Chapter 3 Flashcards
What types of bonding are there
Ionic
Covalent
Metallic
What are the three types of covalent bond
Simple Covalent e.g. H2
Giant Covalent e.g. Diamond
Coordinate (dative covalent)
What is a bond
An attractive force holding particles together
What is ionic bonding
Bonding between a metal and a non-metal
Where electrons are transferred from the metal to the non metal
What is an ionic bond
The electrostatic attraction between oppositely charged ions
What is a covalent bond
It is a bond between non-metals
where electrons are shared between the atoms
What is a covalent bond
It is a shared pair of electrons, and the electron pair is attracted by both nuclei so resists separation
What is a coordinate bond
It is a covalent bond where both electrons in the shared pair originate from the same atom
What is metallic bonding
It is attraction inside a metal between the positive metal ions and the sea of delocalised electrons
Why is there a sea of delocalised electrons in a metal
Outer electron is only weakly held so it becomes delocalised
What determines the shape of a molecule or ion
The number of electron pairs in the outer shell of the central atom
Why do species containing only bonding pairs have regular molecular shapes
Because bonding pairs of electrons exert equal repulsion on each other
What is the shape of an molecule with 2 bonding pairs
It is linear
Bond angle of 180 degrees
Shape of a straight line
What is the shape of molecule with 3 bonding pairs
Trigonal Planar
Bond angle of 120 degrees
Triangle shape
What is the shape of a molecule with 4 bonding pairs
Tetrahedral
Bond angle of 109.5 degrees
Triangular based pyramid
What is the shape of a molecule with 5 bonding pairs
Trigonal Bipyramidal
Bond angles of 90 degrees and 120 degrees
Triangle with another atom opposite the top of the triangle
What is the shape of a molecule with 6 bonding pairs
Octahedral
Bond angle of 90 degrees
Square with two atoms above and below
What does the shape of a molecule also depend on
The presence of non-bonding electron pairs (lone pairs)
Lone pairs take up more space because they are held closer to the nucleus so repel more strongly
What is the shape of a lone pair in a trigonal planar
Bent
Two atoms are slightly bent and at an angle
What are the two shapes of lone pairs in a tetrahedral
1 Lone Pair: Trigonal pyramidal
2 Lone Pair: Bent
What are the 3 shapes with lone pairs in a Trigonal Bipyramidal
1 Lone Pair: Sawhorse
2 Lone Pair: T- shaped, Lone pairs in the middle
3 Lone Pair: Linear
What are the 4 shapes with lone pairs in an Octahedral
1 Lone Pair: Square Pyramidal
2 Lone Pair: Square Planar
3 Lone Pair: T-shaped
4 Lone Pair: Linear
What is the order of decreasing replusion between electron pairs
Lone pair - Lone pair
Lone pair - Bonding pair
Bonding pair - Bonding pair
What is the method to find the shape of a molecule without double bonds
- Count number of outer electrons on the central atom
- add 1 for every atom bonded to the central atom
- For ions add 1 if singly negative, subtract 1 if singly positive
- Total then divide by 2 to get number of electron pairs
- Deduce the regular shape taken up by this number of pairs
- If any of the pairs are lone pairs alter the shape
What happens when two different elements are bonded together
The electron pair is not equally attracted to both nuclei because the elements have different electronegativities
What is electronegativity
It is the power of an atom to attract the pair of electrons in a covalent bond
What affects electronegativity
Nuclear charge
As nuclear charge goes up so does electronegativity
Atomic radius
As atomic radius increases so does shielding which causes electronegativity to decrease
What is electronegativity measured using
Pauling scale
What happens to electronegativity across a period
There is an increasing nuclear charge which means the electron are more attracted to the nucleus so atomic radius reduces and electronegetivity increases
What happens to electronegativity up a group
Fewer energy levels and the outer electrons are less shielded so electronegativity increases
What is used to symbolise which element has a greater electronegativity
A lower case delta is used with a plus and a minus to show the stronger electrongetativity
The negative is used on the stronger one
What is a polar molecule
It is one in which the electron density across the whole molecule is unevenly distributed
What happens when the charge on the molecule isnt symetrical
It is polar overall and described as permanent dipole
What are the 3 types of intermolecular forces
Dipole-Dipole interactions
Hydrogen bonding
Van der Waal’s forces
What is dipole-dipole interactions
They are attractive forces between polar molecules
The polar molecules will flip to give an arrangement where the molecules attract
What are hydrogen bonds
They are very strong intermolecular forces
It takes place when a hydrogen is bonded to a very electronegative element like Oxygen, Fluorine and Nitrogen and there is at least 1 lone pair
What are Van der Waal’s forces
They are temporary dipole - induced dipole interactions
They happen in all molecules
Caused by the movement of electrons, so the more electrons the stronger the force is
What is the order of strength of intermolecular forces at an increasing strength
Van der Waals
Dipole - dipole
Hydrogen bonding
How do two sets of polar molecules or 2 sets of non-polar molecules interact as liquids
They are miscible
but different polar states means that they are non-miscible
What are the 3 states of matter
Solid
Liquid
Gas
What are solids like
They have an arrangement of close and regular and vibrate about a fixed position
What are liquids like
They have an arrangement of random, close and can move past each other
What are gases like
they have an arrangemnet of random, far-apart, rapid and random motion
What is the process solid to liquid
melting
Fusion
What is the process liquid to gas
Boiling
vaporisation
What is the process Gas to liquid
Condensation
What is the process liquid to solid
Freezing
Solidifying
What is the process solid to gas
Sublimation
What are crystals
they are solids that contain particles in a regular arrangement known as a lattice
What are the 4 types of crystal lattices
Ionic
Metallic
Molecular (simple covalent)
Macromolecular (giant covalent)
What are ionic crystals
They are positive and negative ions held together in a giant lattice by strong electrostatic attraction between oppositely charged ions
Properties of ionic compounds
High MP - Strong electrostatic attraction
Conductors as liquid - Ions
Hard and Brittle - Like ions repel
Dissolve in water - Ions become surronded by water
What are metallic crystals
A giant lattice of positive ions held together by a sea of delocalised electrons
Properties of metals
High MP and BP - Strong metallic bonds
Conduct electricity - Sea of delocalised electrons
Malleable and ductile - Ions slide over eachother
Insoluble in water - Water can’t break bonds
What are molecular crystals
Individual molecules held together by weak intermolecular forces
Properties of molecular solids
Low MP - Weak intermolecular forces
Soft - Weak intermolecular forces
Dont conduct electricity - No ions or electrons
What are Macromolecular crystals
A giant arrangement of atoms joined by covalent bonds
Properties of Diamond
High melting point - Strong covalent bonds
Very Hard - Strong covalent bonds
Non-Conductor - No ions or electrons
Properties of Graphite
High MP - Strong covalent bonds
Soft - Weak attraction between layers
Conducts electricity - delocalised 4th electron
