Module 3: Periodic Table And Energy Flashcards
What is the first ionisation energy?
The amount of energy to remove one electron from each atom in a mole of gaseous atoms of an element to form a mole of gaseous 1+(unipositive) ions
What is periodicity?
The general trends that show how properties in elements change as you go across a period
How does atomic radius change as you go across a period?
As you go across a period, the proton number and therefore the nuclear charge increases, which means that the shells are pulled closer to the nucleus, decreasing the atomic radius
How does ionisation energy change as you go across a period, what are the exceptions and why?
As you go across a period, atomic radius decreases and electron shielding doesn’t change so the ionisation energy increases. Between groups 2 and 3, ionisation energy decreases because the valance energy goes from an s sub shell to a p sub shell which is a higher energy level so requires less energy to overcome. Between groups 5 and 6, ionisation energy decreases because the valance electron in group 6 elements are paired with another electron in an orbital so have electron-electron repulsion which decreases the amount of energy needed to overcome it
How does the group an element is in affect its structure and therefore it’s melting point?
Elements in groups 1-3 bond metallically which means there are strong attractions between the metal ions and the delocalised electrons giving them a high melting point, with group 3 elements having the highest of the 3 as there are more delocalised electrons so there’s a stronger attraction. Group 4 elements have the highest melting point because they form giant covalent structures with very strong covalent bonds that are the hardest to break. Groups 5-7 form simple molecules with weak London forces which mean they have very low relative melting points. The bigger the molecule, the higher the melting point as there are more electrons and therefore more London forces
What happens when group 2 oxides react with water?
First they split into group 2 ions and hydroxide ions. Those dissolve in the solution but since the hydroxide ions arent very soluble, not all of them dissolve and instead form a white precipitate
How does solubility and alkalinity change as you go down group 2?
As you go down group 2, solubility and therefore alkalinity/pH increases
How are group 2 compounds used in agriculture and medicine?
Calcium hydroxide(lime) is used in soil to neutralise the acid from acid rain. It forms calcium ions and water. Magnesium hydroxide(milk of magnesium) and calcium carbonate are used in antacids/indigestion pills to neutralise extra stomach acid. Magnesium hydroxide forms magnesium chloride + water, calcium carbonate forms calcium chloride, water and carbon dioxide
What is the bond dissociation energy?
The bond dissociation enthalpy is the energy needed to break one mole of the bond in gaseous molecules to give separated atoms
