B2 redox and periodicity Flashcards
what is oxidisation number on an element?
0
what is the sum of oxidation numbers in a compound?
0
what is the sum of oxidation numbers in an ion?
charge
what is the oxidation number of a group 1 element?
+1
what is the oxidation number of a group 2 element?
+2
what is the oxidation number on F?
-1
what is an oxidation state?
assigned to an element to tell you how many electrons have been lost or gained compared to the unreactive elements.
what is oxidation?
- the loss of electrons.
- the gain of oxygen.
- the increase in oxidation state.
what is reduction?
- the gain of electrons.
- the loss of oxygen.
- the decrease in oxidation state.
what is disproportionation?
when the same element from the same species is both oxidised and reduced at the same time.
what is periodicity?
repeating physical and chemical trends and patterns across the periodic table.
what is the general trend across a period?
protons and electrons increase by 1 and the sub shells fill up.
what is the general trend down a group?
number of electron shells increase by 1 down the group and number of electrons in outer shell stay the same.
what is the affect on atomic radii down a group?
atomic radius INCREASES
- as more electron shells.
what is the affect on atomic radii across a period?
atomic radius DECREASES
- as increased nuclear charge as more protons.
- similar shielding.
- greater attraction between the electrons and nucleus.
what is ionisation energy?
the removal of electrons.
what is the definition of the first ionisation energy?
energy required to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous +1 ions.
what is the equation for the first ionisation energy?
X(g) > X+1(g) + e-
what factors affect ionisation energy?
- atomic radius (or ionic if an ion already).
- nuclear charge/ number of protons.
- shielding (number of shells).
what affect does successive ionisation energies have?
SMALL INCREASE
- less electrons attracted by same number of protons.
- therefore a stronger attraction.
- therefore more energy is required.
what affect does successive ionisation energies have when there are shells?
LARGE INCREASE BETWEEN SHELLS
- electron being removed is closer to nucleus.
- therefore greater attraction.
- therefore more energy required to remove electron.
what happens to the first ionisation energy when going down the group?
DECREASE
- atomic radius increases.
- same nuclear charge.
- weaker attraction between electrons being removed and the nucleus.
- therefore requiring less energy.
what happens to the first ionisation energy when going across the period?
GENERAL INCREASE
- atomic radius is smaller.
- greater nuclear charge.
- stronger attraction between electron being removed and the nucleus.
- therefore require more energy.
why does B have a lower first ionisation energy than Be?
B - electron being removed from p orbital, which is further away from nucleus, therefore less of an attraction.
prove that sub-shells exist.
why does O have a lower first ionisation energy than N?
O - repulsion between paired electrons in 2p orbital, therefore easier to remove electron.
prove that orbitals exist.
what is the trends in giant metallic bonding regarding melting points?
Na & Mg
- Mg has a higher charge of +2 than Na, which is +1.
- Mg has more delocalised electrons than Na.
- therefore stronger electrostatic attraction in Mg.
what is the trend in giant covalent bonding regarding melting points?
Si
- strong covalent bonds in giant covalent structure.
- strong electrostatic attraction.
what is the trend in monoatomic regarding melting points?
Ar
- weak London forces between atoms.
what is the trend in simple molecules regarding melting points?
P4, S8, Cl2
- S8 has the most electrons, therefore has the strongest London forces.
