Periodicity Flashcards
What is periodicity?
Variations in the physical properties of the elements across a period and down a group in the periodic table
When do melting and Boiling Points increase to a maximum?
In the centre of a period, then they decrease
What is covalent radius?
A measure of the size of an atom.
It is defined as the distance between the nuclei of 2 bonded atoms.
Why is covalent radius a periodic property?
It decreases across a period and increases down a group
What results in a smaller atomic size going across a period?
As you go across a period, electrons are being added to the same energy level and Protons are being added to the nucleus, therefore the nuclear charge is increasing.
The greater the nuclear charge, the more strongly the electrons are attracted towards the nucleus, resulting in a smaller size.
What is the first ionisation energy of an element?
The energy required to remove one electron from each atom in one molecule of gaseous atoms
What happens to ionisation energy across a period?
Ionisation energy increases across a period, meaning more energy is required to remove an outer electron.
This is due to the nuclear charge increasing and the atoms being smaller, meaning the outer electron is held closer and more strongly to the nucleus.
What happens to ionisation energy down a group?
Ionisation energy decreases down a group, meaning less energy is required to remove an outer electron.
This is due to the atoms getting bigger and the negative outer electron being further away from the positive nucleus, and so less strongly held in place.
There will also be a greater screening effect as there are more full shells of electrons shielding the outer electron from the attraction pull of the positive nucleus.
Why is there a jump in 2nd and 3rd ionisation energy values?
The large increases are due to the last electron being removed from an inner full shell vs an outer incomplete shell
What is electronegativity?
A measure of the attraction an atom has for its bonded electrons
Why do electronegativity values increase across a period?
The positive nuclear charge increases and thus atoms exert a stronger pull on the shared pair of electrons
Why do electronegativity values decrease down a group?
This is due to the atom size increasing (shared pair of electrons are further away from the nucleus and are less strongly attracted) and the greater screening effect due to more shells of inner electrons between the shared pair of electrons and the nucleus
