Module 3: Periodic table and energy

Question 1

Expand on these points:
The structure of the periodic table
a) the periodic table as the arrangement of elements:
i) by increasing atomic (proton) number
ii) in periods showing repeating trends in physical and chemical properties (periodicity)
iii) in groups having similar chemical properties

Answer 1

Periodic table: Atomic No increases across L and down
Periods: no. period gives no. the highest energy electron shell in an element’s atom
Elements int he same period/group have similar chemical/physical properties.
see diagram on card

Question 2

periodic trend in electron configuration and ionisation energy

b) (i) the periodic trend in electron configurations across Periods 2 and 3 (see also 2.2.1.d)
(ii) classification of elements inot 2-, p- and d- blocks

Answer 2

Trends across period.
* nuclear charge increases
* same shell: similar shielding
* nuclear attraction increases
* Atomic radius decreases - Li Be B C N O F Ne
1st ionisation energy increases
see diagram on card

Question 3

(c) first ionisation energy (removal of 1 mol of electrons from 1 mol of gaseous atoms, X(g) - X+ (g) + e-) and successive ionisation energy and :-
i) explanation of the trend in first ionisation energies across periods 2 and 3 and down a group, in terms of attraction, nuclear charge and atomic radius
ii) prediction from successive ionisation energies of the number of electrons in each shell of an atom and the group of an element.

Answer 3

i) across period
atomic radii decrease
1st ionisation energies increase
He O Ne A
except BE-B
Mg-Al
P-S
N-O
atomic radii increase - shielding increase - nuclear increase not much.
1st ionisation energies decrease - nuclear charge increase but its outweighed by the increase radii and the increase shielding
ii) e.g. Rb group 1 period 5
Therefore ..... 5s sub-shell
therefore high 2nd ionisation energy

Question 4

Periodic trend in structure and melting point

d) explanation of:
(i) metallic bonding as strong electrostatic attraction between cations (positive ions) and delocalised electrons
(ii) a giant metallic lattice structure, e.g. all metals

Answer 4

• +ve ions are balanced by -ve elecrons

* billions of metal ions are held together by metallic bonding in a Giant metallic lattice

Question 5

(e) explanation of the solid giant covalent lattices of carbon (diamond, graphite and graphene) and silicon as networks of atoms bonded by strong covalent bonds.

Answer 5

carbon + silicon - group 4

Therefore 4 electrons in outer shell.
Form covalent bonds with other carbon/silicon atoms
Tetrahedral shape 109.5

Question 6

(f) explanation of physical properties of giant metallic and giant covalent lattices, including melting and boiling points, solubility and electrical conductivity in terms of structure and bonding.

Answer 6

Giant metallic Property Giant covalent
high-strong electro- M.p & b.p high - strong covalent
attraction bonds

insoluble - if any solubility insoluble mostly -
interaction then wd bonds too strong
react not dissolve

Yes when both liquid/ electrical no free electrons -
solid - delocalised conductivity except graphite -
electrons 1 free electron

Question 7

(g) explanation of the variation in melting points across Periods 2 and 3 in terms of structure and bonding

Answer 7

m.p + b.p increase from group 1-4
decrease between group 4 & 5
low between group 5-0

Question 8

Period 3
Na Mg Al Si
metal metal metal giant-covalent
Na* Mg2* Al3* metalloid

And for Period 2?
P S Cl Ar
covalent covalent covalent monatomic
P4 S8 Cl2 Ar

Answer 8

Li and Be are metal
B and C are giant covalent
N2, O2, F2 and Ne are simple molecular

Question 9

Describe 1st, 2nd and 3rd ionisation energies

Answer 9

This measure how easily an atom loses electrons to form +ve ions.
1st: the energy required to remove/electron from each atom in 1 mole of gaseous atoms of an element to form 1 mole of gaseous 1+ ions. X (g) - X+(g) + e-

2nd: the energy required to remove 1 electron from each atom in 1 mole of gaseous 1+ ions of an element to form 1 mole of gaseous 2+ ions.
X+(g) - X2+ (g) + e-

3rd: X2+ (g) - X3+ + e-

Question 10

Al3+ and Na+ ions have = electron arrangements

Explain why more energy is needed to remove an electron from the Al3+ ion than from the Na+ ion

Answer 10

Al3+ is smaller - electrons closer to the nucleus therefore electrons are pulled more strongly by Al3+ and so require more energy to remove.

Question 11

Describe : chemical properties (groups) and electronic structure:

Answer 11

• Noble gases - full outer shells - these arrangements are called CLOSED SHELL arrangments - particulary stable.
• Groups 1 & 2 elements are known as ‘s’ block elements.
• Groups 3,4,5,6,,7, & 0 the outermost ‘p’ sub-shell is being filled therefore they’re known as ‘p’ block elements.
• elements where a ‘d’ sub-shell is being filled are ‘d’ block elements and those where an ‘f’ sub-shell is being filled are ‘f’ block elements.
  see diagram on card