Periodicity

What is meant by periodicity?

When patterns across a period in the periodic table are repeated across other periods as well

How does atomic radius change as you go across a period and why?

It decreases slightly, as there are more protons, and the shielding is the same, so there is a stronger attraction between the nucleus and outer electrons

How does first ionisation energy change across a period and why?

It increases generally, as the atomic radius and shielding is the same, but there are more protons, so an increased attraction between the nucleus and outer electrons

Why does the first ionisation energy decrease from group 2 to group 3?

Group 3 has an extra electron shell, meaning the atomic radius and shielding are greater, making the attraction between the nucleus and outer electrons weaker

Why does first ionisation energy decrease from group 5 to group 6?

The electrons start to pair up in the orbitals, meaning there is repulsion between electrons in the same orbital

How does electronegativity change as you go across a period?

It increases, as there are more protons in the nucleus, so the attraction between the nucleus and the electrons in the covalent bond is stronger

Why do noble gases not have a measured electronegativity?

They have a full outer shell, so do not form covalent bonds

What is the trend in melting and boiling points of metallic substances across a period?

They increase across a period, as the atoms have more protons in the nucleus, meaning the attraction between the positive metal ions and the sea of delocalised electrons is stronger

What is the trend in melting and boiling points of giant covalent substances across a period?

They increase, as bigger atoms means stronger covalent bonds, which means they need more energy to break

What is the trend in melting and boiling points of simple covalent substances across a period?

The bigger the molecule that is made, the stronger the van der waals forces between them, and the higher the melting and boiling points

What is the melting and boiling point of noble gases compared to other in the same period?

It is much lower, as they are monatomic atoms, so there are no bonds that need to be broken.