Unit 1.6 The Periodic Table

Question 1

How are the elements arranged in the Periodic Table?

Answer 1

In the Periodic Table, elements are arranged in order of their atomic number, i.e. the number of protons in the nucleus of each atom of that element.

Vertical columns are called groups.

Horizontal rows are called periods.

There are four “blocks” called s, p, d and f

Metals are usually found towards the left and non-metals towards the right.

Question 2

What does the group number tell you?

Answer 2

The number of electrons in the outer shell of the element.

Question 3

What does the period number tell you?

Answer 3

The period number tells you the number of shells that are occupied.

Question 4

What does the name of the block in which the element is found tells you?

Answer 4

The name of the block and element is found in tells you the orbital the most recent electron was added to.

The block location of an element on the periodic table should match its full electron configuration, and the order of blocks in the periodic table provides a guide to the filing order

Question 5

Tell me the trends in 1st ionisation energy on the periodic table.

Answer 5

• 1st ionisation energy increases across a period
  (due to increase in nuclear charge, no significant additional shielding, slight decrease in atomic radius)
• 1st ionisation energy decreases down a group
  (due to increased atomic radius, increased shielding outweighs additional nuclear charge)
• Gp2 - Gp3 decrease as new outer subshell
• Gp5 - Gp6 decrease as repulsion between paired electrons makes electron easier to remove

Question 6

Define electronegativity.

Answer 6

Electronegativity is the ability of an atom to attract a pair of electrons in a covalent bond.

Question 7

Tell me the trends in electronegativity on the periodic table.

Answer 7

• Electronegativity increases across a period
  (increase in nuclear charge, same shielding so increased attraction to the nucleus)
• Electronegativity decreases down a group
  (increased shielding outweighs additional nuclear charge so attraction to the nucleus decreases)

Question 8

Describe the trend in melting and boiling points on the periodic table.

Answer 8

• The elements in groups 1 - 3 are metals.
  They have high melting and boiling points which increase from group 1 to 3 as the charge on the metal ion increases and there is a greater number of delocalised electrons.
• In group 4, both carbon and silicon have giant covalent structures. This gives them the highest melting and boiling points in period 2 and 3.
• In groups 5 - 7, atoms form simple covalent molecules with low melting and boiling points.
• group 8 elements exist as single atoms so have the lowest melting and boiling point in their period.

Question 9

how do you know if a species has been oxidised?

Answer 9

lost electrons shown by an increase in their oxidation number

Question 10

how do you know if a species has been reduced?

Answer 10

gained electrons shown by a decrease in oxidation number

Question 11

what is the oxidising agent?

Answer 11

the species that caused oxidation and was itself reduced.

Question 12

what is the reducing agent?

Answer 12

the species that caused reduction and was itself oxidised.