Trends in the periodic table Flashcards
What is the trend in covalent radius across a period? And why?
Covalent radius decreases. Across a period number of protons in nucleus increases and so nuclear charge increases and so electrons are more strongly attracted towards the nucleus and the atom will contract in size.
What is the trend in covalent radius down a group?
Covalent radius increases. Down a group number of outer electrons shells increases, this outweighs the increasing nuclear charge due to the shielding effect of filled inner electron shells.
What is screening?
The shielding effect of filled inner electrons shells.
What is electronegativity?
Electronegativity is a measure of the attraction for bonding electrons in a covalent bond.
What is the trend in electronegativity across a period? And why?
Electronegativity increases across a period. Across a period nuclear charge increases and so the attraction of the atom to bonding electrons increases.
What is the trend in electronegativity down a group ? And why?
Electronegativity decreases down a group due to the shielding effect of the additional filled electron shells from the nuclear charge meaning that the electrons are less strongly attracted ti the atom.
What is Ionisation Energy
The energy required to remove one mole of electrons from one mole of gaseous atoms.
What is the trend in Ionisation Energy across a period? And why?
Across a period nuclear charge increases and so the outermost electrons are more tightly held and so the energy required to remove them is greater.
What is the trend in Ionisation Energy down a group ? And why?
Down a group the number of filled electrons shells increases, since the electron is being removed from the outermost electron shell the layer is increasingly distant from the nucleus and so the physical distant from the nucleus and also the screening effect of the inner electron shells overcomes the increased nuclear charge.
Why is the second ionisation energy of sodium so much higher than the first ionisation energy?
Removing the second electron from sodium involves breaking into the second shell of electrons which is much closer to the nucleus and so more tightly held, so more energy is required to remove the electron.
