Topic 3: Periodicity

Question 1

What property is used to arrange the elements in the modern periodic table?

Answer 1

Atomic number (the number of protons in the nucleus of an atom)

Question 2

What is the atomic radius?

Answer 2

The atomic radium “r” is measured as half the distance between neighbouring nuclei.
Determined by:
*The number of electrons shells - the greater the number of shells the larger the atom
*The number of protons in the nucleus - the greater the number of protons in the nucleus the smaller the atom.

Question 3

What blocks are period tables broken into?

Answer 3

”s” “p” “d” and “f” blocks

Question 4

What are the two axis of the periodic table called?

Answer 4

Groups (vertical columns) and Periods (horizontal rows)

Question 5

Ionic radius trend of Positive ions

Answer 5

Positive ions are smaller than their parent atoms, due to the loss of the outer shell

Question 6

Ionic radius trend of Negative ions

Answer 6

Negative ions are larger than their parent’s atoms, due to the addition of electrons into the outer shell

Question 7

Ionic radius trend across the periodic table group 1-14

Answer 7

The ionic radii decrease across a period from Group 1-14. These atoms are iso-electronic (same number of electrons), they have all lost electrons to gain a full outer shell (state e configuration) As you go across a period, you successively add one proton at a time. This means the added protons are able to pull on the same number of electrons. This means the nuclear charge is greater, and the ionic radii decrease.

Question 8

Ionic radius trend across the periodic table group 14-17

Answer 8

The ionic radii decrease across a period from Group 14-17. These atoms are isoelectronic, they have all gained electrons to gain a full outer shell (state e configuration). As you go across a period, you successively add one proton at a time. This means the added protons are able to pull on the same number of electrons. This means the nuclear charge is greater, and the ionic radii decrease.

Question 9

Ionic radius trend down the groups

Answer 9

The ionic radii increase down a group as the number of electron energy levels increases.

Question 10

Ionization energy trend across a period

Answer 10

Ionization energies increase across a period. The increase in effective nuclear charge causes an increase in the attraction between the outer electrons and the nucleus and makes the electrons more difficult to remove.

Question 11

Ionization energy trend down a group

Answer 11

Ionization energies decrease down a group. The electron is removed from the energy level furthest from the nucleus. Although the nuclear charges increase, the effective nuclear charge is about the same owing to the shielding of the inner electrons, and so the increased distance between the electron and nucleus reduces the attraction between them.