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Periodicity and ionisation energy
Terms in this set (51)
What is periodicity?
Repeating trends in the properties of elements across the period
What is ionisation energy?
It measures how easily an atom loses electrons to form positive ions
What is the first ionisation energy?
The energy required to remove one electron from each atom in one mole of gaseous atoms of an element to form one mole of gaseous 1+ ions
How are electrons held in their shells?
By attraction from the nucleus
What are the three factors that affect ionisation energy?
Atomic radius, nuclear charge and electron shielding
How does atomic radii affect the ionisation energy?
The greater the distance between the nucleus and the outer electrons, the less the nuclear attraction
How does the nuclear charge affect the ionisation energy?
The more protons there are in the nucleus of an atom, the greater the attraction between the nucleus and the outer electrons
How does the electron shielding affect the ionisation energy?
Electrons are negatively charged and so inner shell electrons repel outer shell electrons and this repulsion reduces the attraction between the nucleus and the outer electrons
How do you know how much ionisation energy an element has?
It is the same as the amount of electrons they have
What is the second ionisation energy?
It is the energy required to remove one electron from each ion in one mole of gaseous 1+ ions of an element to form one mole of gaseous 2+ ions
What do successive ionisation energies provide?
Important evidence for the different electron energy levels in an atom
What are the three predictions successive ionisation allow to be made about?
The number of electrons in the outer shell, the group of the element in the periodic table and the identity of the element
What happens to the first ionisation energy as you go down the group?
It decreases down a group
Why does the first ionisation energy decrease as you go down the group?
It is due to the fact of the atomic radius increases and therefore the inner shells also increase which in hindsight increases the shielding. Overall, the the nuclear attraction on outer electrons decreases
What happens to the first ionisation energy as you go across the period?
Why does the first ionisation energy increase as you go across the period?
The nuclear charge increases, there is similar shielding, nuclear attraction increases and the atomic radius decreases.
For period 2, how many rises and falls are there for the first ionisation energy?
There are three rises and two falls
What does the fall in the first ionisation energy from beryllium to born mark?
The start of filling the 2p sub shell
Why is the first ionisation energy of boron less than the one of beryllium?
2p sub shell in boron has a higher energy than the 2s sub shell in beryllium, therefore the 2p electron is easier to remove than the 2s electron in beryllium
What does the fall in first ionisation energy from nitrogen to oxygen mark?
It marks the start of electron pairing in the p orbitals of the 2p sub-shell
Why is the first ionisation energy lower in oxygen than nitrogen?
In oxygen, the paired electrons in one of the 2p orbitals repel one another making it easier to remove an electron from an oxygen atom than a nitrogen atom
What are the features of three 2p electrons?
There is one electron in each 2p orbital and it spins at a right angle- equal repulsion as far apart as possible
What are the features of four 2p electrons?
Two electrons in one 2p orbital, 2p electrons start to pair, the paired electrons repel
At room temperature what type of structure are metals?
Solid except for mercury
What is metallic bonding?
Strong electrostatic attraction between cations and delocalised electrons
What does each atom do in a solid metal structure?
It donates its negative outer shell electrons to a shared pool of electrons which are delocalised and spread throughout the structure
When an atom donates it electrons what gets left behind?
The positive ions that consist of the nucleus and inner shell electrons of the metal atoms
What maintains the structure and the shape of the metal?
The positive ions are in fixed position
What are the delocalised electrons able to do?
They are mobile and they are able to move throughout the structure
In a metal structure, what are the billions of metal atoms held together by?
Metallic bonding in a giant metallic lattice
What are the properties of metals?
high melting and boiling points, high electrical conductivity and strong metallic bonds
What happens when a voltage is applied across a metal?
The delocalised electrons can move throughout the structure, carrying charge
What does the melting point for metals depend on?
The strength of the metallic bonds holding together the atoms in the giant metallic lattice
Are metals soluble?
What type of lattice structure does boron, carbon and silicon have?
They are held together by a network of strong covalent bonds to form a giant covalent lattice
How many outer electrons does carbon and silicon have?
What do carbon and silicon use their four electrons for and what does it result in?
To form covalent bonds to other carbon or silicon atoms and it results in tetrahedral structure.
What is the bond angle for a tetrahedral arrangement?
109.5 by electron repulsion
Why do giant covalent lattices have high melting and boiling points?
Covalent bonds are strong and therefore high temperatures are necessary to to provide large amount of energy to break the covalent bond
Why are giant covalent lattice insoluble?
The covalent bonds holding together the atoms in the lattice are far too strong to be broken by interaction with solvents
What are the only two giant covalent lattices that conduct electricity?
Graphene and graphite
Why can't giant covalent lattice conduct electricity?
In carbon and silicon the four outer electrons are involved in covalent bonding so none are available to conduct electricity
Why can graphene and graphite conduct electricity?
Carbon is special in forming several structures in which one electron is available for conductivity
What structures of carbon is good for electrical conductivity?
Planar hexagonal layer
What bond angle does a planar hexagonal layer have?
120 by electron repulsion
What is graphene?
A single layer of graphite
What is graphene composed of?
Hexagonally arranged carbon atoms linked by strong covalent bonds
What metal has the same electrical conductivity as graphene?
What is graphite composed of?
Parallel layers of hexagonally arranged carbon atoms
What are the layers of graphite bonded by?
Weak London forces
What happens to the melting point across period 2 and 3?
It increases from group 1 to 14
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