Chapter 5 - Electrons and Bonding Flashcards
Electron structure, Ionic bonding and structure and Covalent bonding.
What are shells regarded as?
Energy levels
What happens to energy as the shell number increases?
Energy increases
What is the shell number referred to as?
Principal quantum number
What are shells made up of?
Atomic orbitals
How many electrons can be held in an orbital?
One or two
What can an electron be thought of as?
A negative-charge cloud with the shape of the orbital (electron cloud)
What are the different sub-shells and how many orbitals/electrons do they have?
• 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?
Spherical
What is the shape of a p-orbital?
Dumbbell
What are the rules of filling orbitals?
• Orbitals fill in order of increasing energy (note 4s fills before 3d)
• Electrons pair with opposite spins
• Orbitals with the same energy are occupied singly first, then any remaining electrons pair with the already occupying electrons
Why do electrons pair with opposite spins?
• Electrons are negatively charged and so repel one another
• Electrons can have spin up or spin down
• If electrons have opposite spin, the charge repulsion is counteracted enough for both to be in the orbital
Explain why orbitals with the same energy are occupied singly first
• Within a sub shell, orbitals have the same energy
• One electron occupies each orbital before pairing begins, this prevents repulsion until no unoccupied orbitals remain
How can electron configuration be shortened?
• 1s2 = [He]
• 1s2 2s2 2p6 = [Ne]
• 1s2 2s2 2p6 3s2 3p6 = [Ar]
What happens, in terms of sub-shells’ energy, when forming ions?
The highest energy sub-shells loses or gains electrons
What is ionic bonding?
The electrostatic attraction between cations and anions
What is the result of ions attracting oppositely charged ions in all directions?
A giant ionic lattice
How are the melting and boiling points of ionic compounds explained?
• Strong electrostatic attraction between ions
• Lots of energy needed to overcome
• So high m.p and b.p
What happens to the melting points for giant ionic lattices when ionic charge increases?
Melting point increases as there is a stronger attraction between ions
Are ionic compounds soluble?
Yes, in polar solvents (such as water)
What factors does the solubility of an ionic lattice require?
• The ionic lattice must be broken down
• Water molecules must attract and surround the ions to prevent recombination
When can ionic compounds conduct electricity?
• When molten or aqueous
Why can’t ionic compounds conduct electricity when solid?
The ions are in a fixed position (no mobile charge carriers)
Why can ionic compounds conduct electricity when molten or aqueous?
• The solid ionic lattice breaks down.
• So the ions are now free to move (as mobile charge carriers)
What is a general summary of the properties of ionic compounds?
• High melting and boiling points.
• Tend to dissolve in polar solvents
• Conduct electricity when molten or aqueous
What is covalent bonding?
The strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms.
How does covalent bonding differ to ionic bonding?
The attraction is localised, acting only on the shared pair of electrons and the two nuclei of the bonded atoms
How can covalent bonding be displayed?
With dot and cross diagrams
What is a multiple covalent bond?
Two atoms share more than one pair of electrons
What is a double bond?
The electrostatic attraction is between two shared pairs of electrons and the nuclei of the bonding atoms
What is a triple bond?
The electrostatic attraction is between three shared pairs of electrons and the nuclei of the bonding atoms
What is a dative covalent bond?
The shared pair of electrons has been supplied by one of the bonding atoms only (originally a lone pair)
What is an example of a dative covalent bond?
An ammonia molecule donates its lone pair of electrons to a [H]+ ion,
forming an ammonium ion
NH3 + [H]+ → [NH4]+
