Chemical Changes and Structure - Trends in the Periodic Table Flashcards
What is the covalent radius?
A measure of the size of an atom. It is half the distance between the nuclei of two covalently bonded atoms.
How does the covalent radius change going across a period and why?
It decreases going accross a period. Atoms have more electrons in their outer shells and more protons in their nucleus. This means that the electrons become. more strongly attracted to the nucleus (increased nuclear charge) and are pulled in close to the nucleus.
How does the covalent radius change going down a group and why?
The covalent radius increases. The number of occupied electron shells increases. Each extra layer “shields” or “screens” the outer electrons from the nucleus so the outer electrons are less strongly attracted.
What is electronegativity?
Electronegativity is a measure of an atom’s attraction to the electrons in a bond.
How does the electronegativity change going across a period and why?
The electronegativity increases. The atoms increase in nuclear charge and have a smaller covalent radius. This allows the nucleus to attract the bonding electrons more strongly.
How does the electronegativity change going down a group and why?
The electronegativity decreases. The number of occupied electron shells increases. This means the outer electrons are further from the nucleus and less strongly attracted. Also, the extra shells of electrons screen the outer electrons from the nucleus.
What is ionisation energy?
The energy required to remove one mole of electrons from one mole of gaseous atoms.
How does the ionisation energy change going across a period and why?
The ionisation energy increases. The nuclear charge increases, pulling the outer electrons in closer so more energy is required to remove them.
How does the ionisation energy change going down a group and why?
The ionisation energy decreases. The number of electron shells increases meaning the outer electrons are further away from the nucleus and are also being shielded from the nucleus. Less energy is needed to remove the electrons.
