HIGHER CHEMISTRY REVISION.
Unit 1:- Patterns in the Periodic Table
1. The three statements below are taken from a note made by a student studying
trends in the Periodic Table.
1.
First Ionisation Energy
The energy required to remove one mole of electrons from one mole of
atoms in the gaseous state.
(a) Electronegativity.
(b) Increases from left to
2.
The energy required to remove a second mole of electrons .
right.
(c)
After 1st electron
removed the next
electron has to be
taken from energy level
below it, closer to
nucleus. As the 2nd
electron comes from
energy level closer to
the nucleus it is more
firmly attracted to the
nucleus.
Second Ionisation Energy
3.
.....................................................
The measure of the attraction an atom has for the shared electrons in a bond.
(a) Complete the note above to give the heading for the third statement.
(b) What is the trend in the first ionisation energy across a period from left to right.
(c) Why is the second ionisation energy of sodium so much greater than its first
ionisation energy?
2. On crossing the Periodic Table, there are trends in the sizes of atoms and
ions.
(a)
(b)
Why is the atomic size of chlorine less than that of sodium?
Ion
Ionic radius / pm
Si4+
P3-
42
198
Why is there a large increase in ionic radius on going from Si4+ + to P3-?
(a) Chlorine has a larger nuclear charge (17 protons) than sodium
(11 protons). Both atoms have 3 occupied electron energy levels.
The electrons are attracted more by the larger charge in the
chlorine nucleus and so are brought closer to the nucleus.
(b) Si4+ has an electron arrangement of 2,8 – two occupied electron
energy levels. P3- has electron arrangement of 2,8,8 – three
occupied electron energy levels. The third energy level is further
from the nucleus.
3. (a) Complete the table below by adding the name of an element from elements 1 to
20 of the Periodic table for each of the types of bonding and structure described.
Bonding and structure at room
Name of element
temperature and pressure.
metallic solid
sodium
monatomic gas
Neon, argon
covalent network solid
Carbon. silicon
discrete covalent molecular gas
discrete covalent molecular solid
Oxygen, nitrogen, fluorine, chlorine
sulphur, phosphorus
(b) Why do metallic solids such as sodium conduct electricity?
Delocalised electrons allow metals to conduct electricity.
4. Ionisation energies provide information about the structure of atoms.
Write the equation, showing state symbols, for the first ionisation
energy of sodium.
Na(g)
 Na+(g) + e-
4. . (a) Aluminium and phosphorus are close to one another in the Periodic
Table but the P3- ion is much larger than the Al3+ ion.
Give a reason for this difference.
(b) The P3- ion and the Ca2+ ion have the same electron arrangement but
the Ca2+ ion is smaller than the P3- ion.
Give a reason for this difference.
(a) The P3- ion has an electron arrangement of 2,8,8 ie three filled
electron energy levels. The Al3+ ion has an electron
arrangement of 2,8 ie two filled electron energy levels. The
third electron energy level is further away from the nucleus
than the second and so the P3- ion is the larger ion.
(b) Both ions have electron arrangement of 2,8,8 ie three filled
electron energy levels. Calcium has 20 protons in the nucleus
compared to the phosphorus with 15. The 20 protons attract
the three electron energy levels more than the 15 and so the
Ca2+ ion is the smaller.