Periodicity Flashcards
What are the elements sat between the dividing line between metals and non-metals called? What properties do they have?
Metalloids, a combination of metal and non-metal properties
What is the trend of atomic radius down a group?
Increase in principle energy levels, therefore increase in shielding, outer electron is further from the nucleus.
What is the trend of atomic radius across a period?
Decreases as number of protons (nuclear charge) increases, shielding stays constant, electrons are more strongly attracted to the nucleus and atomic radius decreases.
What does periodicity mean?
- Repeating trends of physical or chemical properties
What is ionisation?
Involves the loss of an electron to form a positive ion
Give the definition of the First Ionisation Energy
- The energy required to remove of 1 mol of electrons from 1 mol of gaseous atoms
What is the trend of the 1st IE down a group?
Decreases, electron is removed from a higher principle energy level, electron is further from the nucleus, more shielding, weaker attraction between nucleus and outer electron
What is the trend of the 1st IE across a period?
Increases, number of protons increase, shielding is constant/ atomic radius decreases, stronger attraction between nucleus and outer electron.
What are the two anomalies of the general trend of the 1st IE across period 3? Explain why.
Al and S
Al - IE decreases, electron is removed from a higher energy p sub-level, weaker attraction between nucleus and outer electron
S - IE decreases, pair of electrons in a p-orbital, extra repulsion means less energy required to remove outer electron
Explain successive ionisation energies and explain what they can be used for
- Will always increase, positive charge on ion increases, ionic radius decreases, nuclear attraction on the outer electron increases
- Can be used to find an element’s group number (look for the big jump)
- The big jump happens when an electron has been removed from a principle energy level that is much closer to the nucleus
