Chapter 7 - Periodicity Flashcards
Who was responsible for a more accurate periodic table?
Mendeleev
What did Mendeleev do that was different?
He left gaps for undiscovered elements so that elements fir in patterns
What are the vertical columns in the periodic table called?
Groups
What are the horizontal rows in the periodic table called?
A period
How are the elements in the periodic table ordered?
By proton (atomic) number
4 Properties which vary across a period
Electron configuration
Ionisation energy
Structure
Melting point
How can the periodic table be used to work out electron configuration?
Each period signals the start of a new subshell, so you can read along the period and work out how many electrons are in each sub shell
What is the name for the elements in group 1?
Alkali metals
What is the name for elements in group 2?
Alkaline earth metals
What is the name for elements in groups 3-12?
Transition elements
What is the first ionisation energy of an element?
The energy needed to remove one mole of electrons from one mole of gaseous atoms
Why is ionisation an endothermic process?
It requires energy input
Equation for first ionisation energy
X (g) -> X+ +e-
What does a low ionisation energy indicate?
It is easier to form an ion
3 factors affecting ionisation energy
Nuclear charge
Atomic radius
Shielding
What does a high ionisation energy indicate?
There is strong attraction between the electron and the nucleus so more energy is needed to overcome it and remove the electron
How does nuclear charge impact ionisation energy?
The more protons there are, the stronger the attraction between the nucleus and electron will be
How does atomic radius impact ionisation energy?
The greater the distance between electron and nucleus, the weaker the force of attraction
How does shielding impact ionisation energy?
The more electrons shielding the electron from the nucleus, the weaker the force of attraction
Why does ionisation energy decrease down a group?
There is more electron shielding and the atomic radius is greater
Why does ionisation energy increase across a period?
There is a greater nuclear charge, so a stronger force of attraction
Why does ionisation energy drop between groups two and three?
The outer shell in group 3 is in a p-orbital, rather than an s-orbital. This means it is further from the nucleus and there is additional shielding, so ionisation energy drops
Why does ionisation energy drop between groups 5 and 6?
In group 5 elements, the electron is being removed from a singly occupied orbital, but in group 6, the orbital contains two electrons. The repulsion between the two electrons makes it easier to remove
What are successive ionisation energies?
Removing additional electrons
What can a graph of successive ionisation energies tell us?
When different shells are having electrons removed and how many electrons are in each sub shell
How are metals held together?
Metallic bonding
What is the name for the structure of most metals?
Giant metallic lattice structure
What is metallic bonding?
Delocalised electrons are electrostatically attracted to the positively charged nuclei
What happens when the number of delocalised electrons increases?
Melting point increases
Why are metals ductile and malleable?
There are no bonds holding the layers together so they can slide past each other
Why are metals good thermal and electrical conductors?
The delocalised electrons can carry kinetic energy or electrical charge
Why are metals insoluble?
The metallic bonds are very strong
What are giant covalent lattices?
Huge networks of covalently bonded atoms
What are different forms of the same element called?
Allotropes
Properties of diamond
Very high melting point
Very hard
Insoluble
Can’t conduct electricity
Why does diamond have such specific properties?
All four of its outer carbons are bonded to another carbon
Why is graphite used as a lubricant?
Weak forces between layers
Why can graphite and graphene conduct electricity?
Delocalised electrons to carry charge
Why is graphite less dense than diamond?
The layers are far apart
Why does graphite have a high melting point?
It has strong covlent bonds
Why is graphite insoluble?
The covalent bonds in the sheets are very strong
Why is graphene so strong?
Delocalised electrons strengthen covalent bonds
What is a simple molecular structure?
A structure containing only a few atoms
Why do simple molecules have low melting points?
Weak induced dipole-dipole forces to overcome
Why do noble gases have low melting points?
They are monatomic, meaning weak dipole-dipole forces
Why does melting point change across a period?
The type of bond formed changes
What will happen to the melting point of metals across a period?
It will increase - the number of delocalised electrons increases so the bonds are harder to overcome
Why so carbon and silicone have high melting points?
They form giant covalent lattices, which require lots of energy to overcome
Why are giant covalent lattices insoluble?
The covalent bonds holding the atoms in the lattice are far too strong to be broken by solvents
Across period 2 and 3, what happens to melting points between groups 1 and 14?
There is an increase
What happens to melting points of elements in groups 15-18 in periods 2 and 3?
They decrease
In periods 2 and 3, why does melting point decrease between group 14 and 15?
The elements in group 15 onwards form simple molecular structures, not giant, which require less energy to overcome
How does the bonding in a simple molecular lattice differ to that in a giant covalent lattice?
A simple molecular lattice only has London forces between atoms, whereas a giant covalent lattice has covalent bonds
Why does the melting point of metals increase with the number of electrons?
The number of delocalised electrons and the charge of the ion increase, which makes the metallic bonds stronger and harder to break
