"Electronegativity increases as you move across periods left to right and decreases as you move down groups".
Explain this trend with reference to the following periodic table. (4 marks)
Moving from left to right:
→ As you move across a period from left to right in the same row, the number of protons in the nucleus of elements increases in accordance with their atomic number.
→ eg. \(\ce{Li}\) (far left) has 3 protons in its nucleus whereas \(\ce{F}\) (far right) has 9 protons in its nucleus.
→ This leads to a greater attractive force and thus higher electronegativity.
Moving down within a group (column):
→ Adding electron shells to a nucleus decreases electronegativity.
→ This is due to an increase in atomic radius and the effect that extra electron shells have in shielding the attractive forces of protons.
→ All the elements in a period (row) further down the periodic table have an extra electron shell than the period directly above them, decreasing electronegativity as you move down.
Moving from left to right:
→ As you move across a period from left to right in the same row, the number of protons in the nucleus of elements increases in accordance with their atomic number.
→ eg. \(\ce{Li}\) (far left) has 3 protons in its nucleus whereas \(\ce{F}\) (far right) has 9 protons in its nucleus.
→ This leads to a greater attractive force and thus higher electronegativity.
Moving down within a group (column):
→ Adding electron shells to a nucleus decreases electronegativity.
→ This is due to an increase in atomic radius and the effect that extra electron shells have in shielding the attractive forces of protons.
→ All the elements in a period (row) further down the periodic table have an extra electron shell than the period directly above them, decreasing electronegativity as you move down.