Periodicity Flashcards
What is the trend in melting point across a period 3?
Increase and then decrease. Across period 3 there is an increase from Na to Al due to there being a stronger attraction between metal ions and delocalised electrons. Ions are smaller , so there is an increase effect of nuclear charge this means more energy is required to overcome. There is an increase again from Al to Si as silicon has a giant covalent bond, each Si has 4 covalent bonds. There is then a decrease from Si to P as phosphorus is a non metal so only has weak van der waals between molecules which require little energy to overcome.
What is the trend in atomic radii across a period ?
The atomic radii decreases across a period, this is because as you move across a period you are adding protons to the nucleus and electrons to the outer shell, this charge pulls the electrons in closer to the nucleus due to the increased effect of nuclear charge, no additional electron shells.
What is the trend in atomic radii down a group?
Atomic radius increases down a group this is because the number of electron shells increases , so there is a lower effect of nuclear charge as outer electron is further away from the nucleus.
What is the trend in ionisation energy across a period?
Ionisation energy increases as the number of protons increases within the same shielding, the increase in nuclear charge makes it increasingly difficult to remove an electron so more energy is required.
What is te trend in ionisation energy down a group?
Th number of electron shells increases, so there is an increased shielding , this reduces the affect of nuclear charge meaning less energy is required to remove an electron.
