Chapter 7

• Groups in the periodic table have similar chemical properties • This is because the elements have the same number of electrons in their outer shell

• Repeating trends in the physical and chemical properties of elements across a period

• Electronic configuration • Ionisation energy • Structure • Melting points

• Each period starts with an electron in the new highest energy level

• The energy required for the removal of 1 mol of electrons from 1 mol of gaseous atoms of an element

• Cl (g) -> Cl+(g) +e- (it is not shown as diatomic as first ionisation energy refers to 1 mol of atoms)

• The amount of energy needed to turn 1 mol of gaseous 1+ ions into 1 mol of gaseous 2+ ions

• Atomic radius • Nuclear charge • Electron shielding

• The greater the distance between the nucleus and the outer electrons, the less the nuclear attraction

• The more protons there are in the nucleus of an atom, the more positively charged it is, and so the greater the attraction between the nucleus and the outer electrons

• Electrons are all negatively-charged and therefore repel each other, meaning that inner-shell electrons repel outer-shell electrons • This reduces the attraction between the nucleus and the outer electrons

• They increase • There is a big increase in the ionisation energy between different shells of an atom

• The nuclear attraction between the remaining electrons and nucleus increases (the same number of protons attract fewer electrons) • The atomic radius therefore decreases

• They decrease down a group • They generally increase across a period

• The atomic radius and shielding increases • Nuclear attraction on outer electrons decreases

• The nuclear charge increases, which causes the atomic radius to decrease • There is similar shielding • The nuclear attraction therefore increases

• Between groups 2 and 3 • Between groups 5 and 6

• In group 3, the p sub-shell starts to be filled • As it has more energy than the s sub-shell, it is easier to remove the electron in the p sub-shell • Group 3 therefore has lower first ionisation energy than group 2

• In group 6, the p sub-shell electrons start to pair up • The paired electrons in one orbital repeal each other, making it easier for one of them to be removed • Therefore, group 6 has a lower first ionisation energy than group 5

• The highest points are the noble gases • The lowest points are the group 1 metals • First ionisation energy generally increases across each period • There are dips between groups 2 and 3 and 5 and 6 • Each period has a lower first ionisation energy than the previous period (the entire line is shifted down)

• The strong electrostatic attraction between cations and delocalised electrons

• They are giant metallic lattices

• High electrical conductivity • High melting and boiling points

• When in the solid or liquid states • This is because the delocalised electrons are free to move through the structure and carry charge