2.2 Electrons, Bonding And Structure
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How many electrons are in the 1st energy level?
2
How many electrons are in the 2nd energy level?
8
How many electrons are in the 3rd energy level?
18
How many electrons are in the 4th energy level?
32
How many orbitals and electrons are in: S P D F
S-1 orbital, 2 electrons P-3 orbitals, 6 electrons D-5 orbitals, 10 electrons F-7 orbitals, 14 electrons
What is the shape of an s orbital and a p orbital?
S orbital - spherical P orbital - dumbbell (3 p orbitals at right angle to each other)
Define an oribital
A region around the nucleus that can hold up to two electrons, with opposite spins
What is the filling order to work out electron configuration?
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p, (8s, 5g, 6f, 7d, 8p, and 9s)
How can we explain the electron configuration for chromium and copper
Sub-shells like to be full or half full. As 4s and 3d are so close in energy, electrons can move between them easily, and rearrange to make full and half full sub shells
What’s an ionic bond?
Electrostatic forces of attraction between two oppositley charged ions
Describe sodium chloride
NaCl has a giant ionic lattice Each ion is electrostatically attracted in ALL directions to ions of the opposite charged NaCl is cube shaped Lots of energy needed to break up lattice High melting point (801℃)
Explain the 3 behaviours of ionic compounds
• Conduct electricity when molten or dissolved • high mp and bp • tend to dissolve in water as water molecules are polar (parts of molecule have negative and others have positive charge pulling apart lattice)
What’s a covalent bond?
The strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms
What is Dative covalent bonding? How is it shown in diagrams?
Its when both electrons come from one atom It is shown in diagrams by an arrow pointing away from the donor atom OR when only dots are in the dative covalent bond part In a dot and cross diagram ie NH4+ where the nitrogen atom donates 2 electrons to a H+ proton.
What does the phrase ‘expand the octet’ mean?
When some compounds can use the d orbital to ‘expand the octet’. So can have more then 8 electrons in the outer shell. ie sulfur hexafluoride where sulfur Has 12 electrons in its outer shell.
What is average bond ?
• Measures how much energy is required to break a covalent bond • The higher the bond enthalpy the stronger the bond
Are lone pairs or bonding pairs more electron dense?
Lone pairs are more electron dense so repel more
Aufbau principle
Electrons enter the lowest possible energy level
Hund’s rule of maximum multiplicity
When in orbitals of equal energy electrons will try and remain unpaired
Raul’s exclusion principle
2 electrons can go in each orbital provided they are of opposite spin
Lone pair/lone pair bonding pair/bonding pair Lone pair/Bonding pair Which angle is the biggest? Which angle is the smallest?
Biggest angle: Lone pair/lone pair Smallest angle: Bonding pair/ bonding pair
What’s the shape and bond angles of a molecule with 2 bonded pairs?
180˚ Linear molecule BeCl2
What’s the shape and bond angles of a molecule with 3 bonded pairs?
120˚ Trigonal planar BF3
What’s the shape and bond angles of a molecule with 4 bonded pairs, no lone pairs?
109.5˚ tetrahedral NH4+