Periodic table trends

Question 1

The periodic table at a glance

Answer 1

• The periodic table lists all known elements by their atomic number.
• The periodic table is also arranged into groups and periods.

Question 2

Characteristics of the periods

Answer 2

• Periods are the horizontal rows. The period number represents the number of occupied electrons shells in the atoms of the elements. Thus all elements in the same period have the same number of occupied electron shells.
• They also share a gradual change in their physical and chemical properties.

Question 3

Characteristics of the groups

Answer 3

• Groups are the vertical colums. The group number represents the number of valence electrons in the atoms of the elements. Thus all elements in the same group have the same number of valence electrons.

Question 4

The groups

Answer 4

Group 1: Alkali Metals
Group 2: Alkaline Earth Metals
Group 17: Halogens
Group 18: Noble Gases

*noble gases are not reactive because they are stable and already have a full outer shell.

Question 5

Electronegativity

Answer 5

• Electronegativity measures the tendency of an atom to gain/attract electrons during a chemical bonding process.
• When an atom has a high electronegativity, it means that it easily gains electrons and low electronegativity means that it easily loses electrons.

Question 6

Donators and acceptors

Answer 6

• Electron donators are metallic elements, found at the left hand side of the periodic table.
• Electron acceptors are non-metallic elements, found at the right hand side of the periodic table.

Question 7

Metals and non-metals

Answer 7

• The diagonal step line starting at Boron separates metals (left of the line) from non-metals (right of the line).
• The change from metallic to non-metallic character is gradual, therefore some elements have both metallic and non-metallic characteristics, these are called metalloids (semi-metals).

Question 8

How characteristics of an element change across the periodic table

Answer 8

• As you move from left to right diagonally, there is an increase in non-metallic character and as you move right to left diagonally, there is an increase in metallic character.
• Ionisation energy and electronegativity increase from left to right and down to up.
• Atomic number/number of protons increases left to right.
• Atomic radius increases right to left and up to down.
• Reactivity decreases left to right and up to down.