Download Trends in Periodic table

Trends in Periodic table
1. Define the following
1st ionisation energy: Minimum energy required to completely remove the most loosely bound
electron from a mole of gaseous atoms in their ground state
2nd ionisation energy: The energy needed to remove a second electron from each ion in a mole of ions
of gaseous atoms in their ground state
Electronegativity: Is the relative attraction that an atom in a molecule has for the shared pair of electrons
in a covalent bond
Atomic radius: of an atom is defined as half the distance between the nuclei of the two atoms of the
same element that are joined together by a single covalent bond
2. Account fully for the trends in 1st ionisation energy across period 2 of the periodic table.
Increases: due to increase in nuclear charge, decrease in atomic radius, no effect on screening effect
3. Account fully for the trends in 1st ionisation energy down group 2 of the periodic table.
Decreases: due to increase in atomic radius, increase in screening effect
4. Explain the following
a) The 1st ionisation energy of sodium is relatively low, while its 2nd ionisation energy is very high.
Give full explanations
st
I ionisation is low due to half full 3s sub level which is more stable when it looses 1 electron to have a
full shell underneath. 2nd ionisation energy is very high because it requires a lot of energy to remove an
electron from a full 2p sublevel
b) The first ionisation energy of Nitrogen is higher than expected
Due to half full p sub level which is more stable hence requires more energy
5. Write balanced equations for the 1st and 2nd ionisation energys of X ( include state of matter as a
subscript)
X(g)= X+ (g)+ 1eX+(g) = X2+(g) + 1e6. What is the unit for ionisation energy
Kj/mole
7. Would it take more or less energy to remove the most loosely bound electron from an atom with a
ground state electron or an excited electron. Explain why.
More energy to remove an electron from a ground state atom. In an excited atom the electrons are
further from the nucleus so easier to remove
8. Account for the reactivity of alkali metals as you move down the group
Increases due to decreasing electronegativity so more readily gives away electrons. Caused by
increasing atomic radius and increased screening effect
9. Account for the reactivity of halogens as you move down the group
Decreases due to decrease in electronegativity so less able to attract electrons. Caused by increases
in atomic radius and increase in screening effect .
10. Look at the chart and answer the following questions
Account for high 1st ionisation energy for
a) He requires alot of energy to remove an electron from full 1s sublevel because more stable
b) Be requires alot of energy to remove an electron from full 2s sublevel because more stable
c) N requires alot of energy to remove an electron from half full 2p sublevel because more stable
Why is the 2nd ionisation energy of Boron a lot higher than expected
It is higher than expected because your now trying to remove an electron from a full 2s sublevel
which is more stable. ( 2nd ionisation energy is always higher due to smaller atomic radius and a
greater nuclear charge than electronic charge)
Give 2 reasons why the 2nd ionisation value is greater than the 1st ionisation value in most elements
2nd ionisation energy is always higher due to smaller atomic radius and a greater nuclear charge
than electronic charge