3.1.1 periodicity

Have similar physical and chemical properties Atoms of elements in a group have similar outer shell electron configurations, resulting in similar chemical properties

Elements are classified based on which orbitals the highest energy electrons are in

Repeating pattern of properties across different periods

Decreases across a period as increase proton number creates more positive charge attraction for electrons which are in the same shell Similar shielding

Energy needed to remove an electron from each atom in one mole of gaseous atoms H(g) > H+(g) + e-

Attraction of nucleus (the more protons the greater the attraction) The distance of electrons from nucleus (the bigger the atom the further the outer electrons are from the nucleus and the weaker the attraction to the nucleus) Shielding of attraction of nucleus (an electron in outer shell is repelled by electrons in complete inner shells, weakening the attraction of the nucleus)

Always larger than first ionisation energy This is because the ion formed, is smaller than the atom and the proton to electron ratio in the 2+ ion is greater than the 1+ ion Attraction between nucleus and electron is therefore stronger

It’s first electron is in the first shell closest to the nucleus and has no shielding effects from inner shells Has a bigger first ionisation energy than H as it has one more proton

As one goes down a group, the outer electrons are found in shells further from the nucleus more shielded so the attraction of the nucleus becomes smaller

As one goes across a period the electrons are being added to the same shell which has the same distance from the nucleus and same shielding effect. The number of protons increases, however, making the effective attraction of the nucleus greater.

This is because Na will have its outer electron in a 3s shell further from the nucleus and is more shielded. So Na’s outer electron is easier to remove and has a lower ionisation energy.

Al is starting to fill a 3p sub shell, whereas Mg has its outer electrons in the 3s sub shell. The electrons in the 3p subshell are slightly easier to remove because the 3p electrons are higher in energy and are also slightly shielded by the 3s electrons

With sulphur there are 4 electrons in the 3p sub shell and the 4th is starting to doubly fill the first 3p orbital. When the second electron is added to a 3p orbital there is a slight repulsion between the two negatively charged electrons which makes the second electron easier to remove.

the electrostatic force of attraction between the positive metal ions and the delocalised electrons

Number of protons - the more protons the stronger the bond Number of delocalised electrons per atom - the more delocalised electrons the stronger the bond Size of ion - the smaller the ion, the stronger the bond

Giant molecular structure Tetrahedral - 4 covalent bond per atom

Planar arrangement of carbon atoms in layers 3 covalent bonds 4th outer electron per atom is delocalised so can carry charge

High due to many strong covalent bonds Take a lot of energy to break

Diamond and sand - poor as electrons cant move Graphite - good as free delocalised electrons between layers

Poor

High - strong electrostatic forces between positive ions and sea of delocalised electrons

Good - delocalised electrons can move through structure

Shiny metal Malleable as the positive ions in lattice are all identical so, planes of ions can easily slide over one another