3.1.1 - Periodicity
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How are the elements arranged in a periodic table?
They are arranged in the order of increasing atomic numbers
What is a period on a periodic table?
The horizontal rows in the periodic table
What is a group on a period table?
The vertical columns
What is meant by periodicity?
The repeating trends in chemical and physical properties
What change happens across each period?
Elements change from metals to non metals
How can the electron configuration be written in short?
The noble gas before the element is used to abbreviate e.g. Li —> 1s2 2s1 ; Li ——> [He] 2s1
Define first ionisation energy
The energy required to remove one mole of electrons from one mole of atoms in a gaseous state, to form one mole of 1+ ions also in their gaseous state
Write an equation for the first ionisation energy of magnesium
Mg (g) —–> Mg+ (g) + e-
What are the factors that affect ionisation energy?
Atomic radius Nuclear charge Electron shielding
Explain the trend on this graph
First ionisation energy increases across period 3 because of: increased nuclear charge Decreased atomic radius Same electron shielding Which means that more energy is needed to remove the first electron Dips at Al because: outer electron is in 3p orbital, higher energy than 3s orbital less energy is needed to remove electron Dips at S because: one 3p orbital contains 2 electrons Repulsion between paired electrons Less energy is needed to remove electron
Why does first ionisation energy decrease between group 2 to 3
Decrease between 2 o 3 because in group 3, the outermost electrons are in p orbitals whereas in group 2 they are in s orbital, so the electrons are easier to be removed
Why does first ionisation energy decrease between group 5 to 6?
The decrease between 5 to 6 is due to the group 5 electrons in p orbital are single electrons and in group 6, the outermost electrons are spin paired, with some repulsion. Therefore the electrons are slightly easier to remove.
Does first ionisation increase or decreases between the end of one period and the start of the next? Why?
Decrease There is increase in atomic radius Increase in electron shielding
Does first ionisation increase or decrease down a group? Why?
Decrease Shielding increases —> weaker attraction Atomic radius increases —-> distance between the outer electron and the nucleus increases —> weaker attraction Increase in number of protons is outweighed by increase in distance and shielding
What are the properties of giant metallic lattices? (4)
High melting and boiling point Good electrical conductors Malleability Ductility
What is a ductile metal?
The metal can be made stretched eg. can be made into wires
What is a malleable metal?
The metal can be shaped into different forms
Describe the structure, forces and bonding in every element across period 2
Li and Be —–> giant metallic; strong attraction between psoitive ions and delocalised electrons; metallic bonding B and C ——> giant ocvalent; string forces between atoms; covalent bonding N2, O2, F2, Ne —–> simple molecular; Weak intermolecular forces between molecules; Covalent bonding within molecules and intermolecular forces between molecules
Describe the structure, forces and bonding in every element across period 3
Na, Mg, Al —-> giant metallic; Strong attraction between positive ions and delocalised electrons; metallic bonding Si ——> Giant covalent; Strong forces between atoms; Covalent bonding P4, S8, Cl2, Ar —–> Simple molecular; Weak intermolecular forces between molecules; Covalent bonding within molecules and intermolecular forces between molecules