Periodicity Flashcards
what is periodicity?
The repeating pattern of properties of elements across different periods in the periodic table
How are elements arranged in?
order of atomic number
How do the elements in period 2 resemble closely to the elements in period 3?
In terms of that repeating chemical behaviour and physical properties, the elements in groups have similar chemical properties
what do elements in the same period have?
A similar electron core
what is the first ionisation energy?
The energy required to move one mole of electrons from one mole of gasesous atoms
What is ionisation?
-The removal of an electron from an atom to make a positive ion
what happens when an electron is removed?
The atom has been ionised
what is generally called the ionisation energy?
Energy needed to remove electrons from the atom
Why is ionisation an endothermic process?
because energy is needed to overcome the electrostatic force of attraction between the negative electron and the positive nucleus
What are the factors influencing the magnitude of ionisation energy?
(attraction)
-nuclear charge
-distance of electrons from nucleus (atomic/ionic radius
-shielding effect
What does more protons mean for nuclear charge?
the greater the nuclear charge
when is nuclear attraction reduced?
With increasing distance (the further, the electron is from the nucleus the easier it is to remove)
How does the shielding affect work?
-inner the shell electrons repel outer of shell electrons
-this repelling effect, reduces the attraction experience by the outer electrons from the nucleus
-Electrons in inner shell shield outer electrons from the attractive force of the nucleus
what happens to ionisation across a period? (NcArss)
-nuclear charge in increases
-outer electron in the same sub shell (atomic radius decreases)
-shielding the same
-Nuclear attraction increases
-Therefore electron requires more energy to remove
-So ionisation energy increases across the period
What happens to ionisation energy down the group?
-nuclear charge increases (outweighed by changes in shielding and shells)
-outer electron in new shell (atomic radius increases)
-Shielding increase
-Nuclear attraction decreases
-therefore electron requires less energy to remove
-So ionisation energy decreases down a group
what does electron repulsion mean?
Electron is easier to remove
What can electronic configurations of elements be predicted from?
successive ionisation energies
what do successive ionisation energy provide?
Evidence for different energy levels
how many ionisation energies does an element have?
it has as many ionisation energies as it has electrons
Why does the ionisation energy increase each time an electron is removed?
-as an electron is removed nuclear attraction increases as there are more protons than electrons (the proton:electron ratio increases)
Why is the third ionisation energy much greater than the second in mg?
-there is a massive change because the third electron is removed from a lower shell
why are the third to tenth successive ionisation energies of similar order (in magnesium)?
-this is because they are all removed from the same shell so similar amount of energy needed
-they all experience similar shielding from the nucleus
why is there a large difference in value between the 10th and 11th ionisation energy? (in magnesium)
-because the 11th electron is on a different shell (removed from the fist main energy shell)
what happens to metallic character as we go from left right?
It decreases
What structure do all metals have?
giant metallic lattice structure
What is the definition of metallic bond?
The strong electrostatic attraction between cations (positive ions) and delocalised electrons.
what are the electrons in the outer shell of a metal?
-The electrons are delocalised to give positive metal centres (cations)
what metal ions does Na form?
Na+
what metal ions does mg form?
mg2+ ions
what is the arrangement of a giant metallic lattice structure?
-fixed metal cations are surrounded by mobile, delocalised electrons
What do the mobile delocalised electrons mean?
metals can conduct as both solids and liquids
What do the strong metallic bonds in metals mean?
-High temperatures are needed to provide a large amount of energy needed to overcome the electrostatic attraction between the cations and electrons
What do metals tend to have?
high melting and boiling points
what are giant covalent lattices is held together?
The are held together by a network of strong covalent bonds
what does strong covalent bonds need to overcome them?
A large amount of energy
what do giant covalent materials have?
-High melting and boiling points
why are covalent materials insoluble in most solvents?
-The covalent bonds are too strong to be broken by interactions with solvent molecules
why can most covalent structures not conduct electricity?
all the outer shell electrons are involved in covalent bonding
why can graphite and graphene conduct electricity?
They have mobile electrons
What is the melting/boiling point of particular element dependent on?
The bonding present in the structure of the element
Why do metals have high melting points?
Because they contain metallic bonding
why do non-metals with giant covalent structures (like silicon) have high melting points?
they have high melting points because the covalent bonds are strong and require large amounts of energy to break
why do simple covalent molecules (like phosphorus and chlorine) have low melting and boiling points?
-because they are held together by intermolecular forces, which are weaker and require less energy to overcome
why do metals conduct electricity?
because their giant structures contain delocalised electrons which are mobile
What does metallic character increase?
-Conductivity to a maximum in group 3
when does metallic character increase?
Down the group
why do elements be on the silicon show no conduction?
-all electrons are involved in bonding and are not mobile
