3.1.1 Periodicity Flashcards
define periodicity
describe the periodic table in terms of arrangement of elements
They are arranged:
-by increasing atomic (proton) number
- in periods showing repeating trends in physical and chemical properties
- in groups having similar physical and chemical properties, due to having the
same number of electrons in the outer shell
why do elements in the same group have similar chemical properties?
because the have the same outer shell electron configurations, resulting in similar properties
define first ionisation energy
the energy required to remove one electron from each atom in one mole of gaseous atoms to form one mole of 1+ ions
why do ionisation energies increase across a period?
As you go across a period, the number of protons increases, increasing nuclear charge, resulting electrons being more attracted to the nucleus and so more energy is required to remove an electro from the outer shell
why do ionisation energies decrease down a group
-Down a group, the number of shells increases. This increases the atomic radius
so therefore the attraction between the nucleus and the electrons is less. So
ionisation energy decreases.
-Down a group, there are more inner shells so there is increased shielding
between the nucleus and outer electrons so less attraction between the nucleus
and the outer electrons thus less energy is needed to remove them.
how do Successive ionisation energies provide evidence for the shell structure of atoms?
- this is because as electrons are removed from an atom, successive ionisation energies increase as there is less repulsion between electrons
- Between shells, there are big jumps in ionisation energies, as the electron is removed from a shell closer to the nucleus so its attraction is stronger so more energy is required to remove it
what are the factors affecting first ionisation energies
- Atomic radius- The larger the atomic radius, the further away the outer electrons are held from the nucleus, and the smaller the nuclear attraction.
- Nuclear charge- The greater the nuclear charge, the greater the attractive force on the outer electrons so more energy is needed to remove an electron.
- Shielding- electrons repel each other due to their negative charge. The greater the number of inner shells of electrons, the greater the repulsion of the outer shell of electrons.
what is a successive ionisation energy?
define second ionisation energy
the energy required to remove one electron from one mole of gaseous 1+ ions to form one mole of gaseous 2+ ions
define metallic bonding
metallic bonding as strong electrostatic attraction between cations (positive ions) and delocalised electrons
describe the structure of a giant metallic lattice
A large 3-dimensional structure made of positive metal ions, with a sea of delocalised electrons in between, resulting in metallic bonding between them
