periodicity

Question 1

What is the trend in metallic character across a period

Answer 1

decreases gradually

Question 2

What is the trend in ionisation energies across a period?

Answer 2

Ionisation energies increase so it becomes more difficult to remove electrons as greater nuclear charge- covalent bonding more common crossing a period from left to right

Question 3

What type of bonds do noble gases form?

Answer 3

Neither metallic or covalent as ionisation energies too high for metallic, and no unpaired electrons for covalent. So noble gases exist as free gaseous atoms

Question 4

Describe the structure and physical properties of sodium, magnesium and aluminium:

Answer 4

Metals, consisting of a lattice of positive ions held together by a sea of delocalised electrons. Fairly strong attraction between the positive metal ions and the delocalised electrons so tend to have fairly high melting and boiling points

Question 5

What is the trend in melting points of metals across a period?

Answer 5

Increase with increasing charge and decreasing size so the melting points increase across a period

Question 6

Describe the structure and physical properties of silicon:

Answer 6

Giant covalent/macromolecular
Forms giant lattices in which all the atoms are held together by strong covalent bonds. Structure cannot be broken up without breaking these strong covalent bonds so silicon has a very high melting and boiling point. Tetrahedral structure. Does not conduct electricity well as no free e- or ions

Question 7

Describe the structure and physical properties of phosphorous, sulfur chlorine and argon:

Answer 7

Simple molecular structures, with strong covalent bonds within the molecule. However only held together by weak van de waals forces. Relatively low melting and boiling points. Don’t conduct electricity as they have no free electrons or ions

Question 8

Order sulfur, phosphorous, chlorine and argon according to melting point:

Answer 8

Sulfur>Phosphorous>Chlorine>Argon
The larger the molecule, the greater the magnitude of the temporary dipole-dipole and the higher the melting and boiling points. Sulfur exists as S8 so is quite large and has quite strong van de waals forces. Phosphorous exists as P4 so smaller and weaker Van de waals. Chlorine is Cl2 so much smaller molecule and thus lower melting point. Argon has lowest as exists as single Ar atoms so forms only very weak van de waals forces.