Explain the trend in first ionisation energy as you go across Period 3

Overall, the first ionisation energies will increase. This is because as you go along the period, the atomic number increases and this causes a stronger electrostatic attraction between the outer electrons and the nucleus. There are 2 "dips" in this trend. There is a drop in energy from Magnesium to Aluminium. This is because in magnesium the outer electrons are in a 3s orbital, whereas in aluminium the outer electron is in a 3p orbital. The 3p orbital is further from the nucleus, and hence there is more electron shielding and distance from the nucleus so electrostatic attraction decreases. The second drop is from Phosphorus to Sulphur. This is because it is the first time electrons are paired up in 3p orbitals, so there is added electron-electron repulsion.

CW
Answered by Charles W. Chemistry tutor

15830 Views

See similar Chemistry A Level tutors

Related Chemistry A Level answers

All answers ▸

The boiling points of ammonia (NH3), fluorine (F2) and bromine (Br2) are -33, -188 and +59 degrees celsius respectively. Explain the differences in these boiling points, including the names of any relevant forces and particles.


Formic acid (CH2O2) is used as an antibacterial on livestock feed. A sample of formic acid has been found to have a pH = 3, and data shows it has a Ka = 1.6E-4 M. What is the concentration of the sample?


How does hydrogen bonding work?


Why doesn't chlorine form hydrogen bonds even though it is more electronegative than nitrogen?


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences