3.1.1 Periodicity Flashcards
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 periodic 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 -> 1s²2s¹
- Li -> [He] 2s¹
Define first ionisation energy.
- The energy required to remove one electron from each atom in one mole of the gaseous element to form one mole of gaseous 1+ ions
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 or screening
Explain the trend on this graph.
- First ionisation energy increases across period 3 because of:
- Increased nuclear charge
- Decreased atomic radius
- Same electron shielding
- This means more energy is needed to remove the first electron
- Dips at Al:
- Outer electron is in a 3p orbital, higher energy than 3s orbital -> less energy needed to remove the electron
- Dips at S:
- One 3p orbital contains two electrons -> repulsion between paired electrons -> less energy needed to remove one
Why does first ionisation energy decrease between group 2 to 3?
- Decrease between 2 to 3 because in group 3 the outermost electrons are in p orbitals, whereas in group 2 they are in s orbitals
- This makes the electrons easier to remove.
Why does first ionisation energy decrease between group 5 to 6?
- The decrease between 5 to 6 is due to:
- Group 5 electrons in p orbitals being single electrons
- Group 6 electrons being spin-paired with some repulsion
- This makes the electrons slightly easier to remove
Does first ionisation energy increase or decrease between the end of one period and the start of the next? Why?
- Decrease
- There is an increase in atomic radius
- There is an increase in electron shielding
Does first ionisation energy increase or decrease down a group? Why?
- Decrease
- Shielding increases -> weaker attraction
- Atomic radius increases -> distance between the outer electrons and nucleus increases -> weaker attraction
- The increase in the number of protons is outweighed by the increase in distance and shielding
What are the properties of giant metallic lattices?
- High melting and boiling point
- Good electrical conductors
- Malleability
- Ductility
What is a ductile metal?
- The metal can be stretched.
- E.g., 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 & Be: Giant metallic structure
- Strong attraction between positive ions and delocalised electrons
- Metallic bonding
- B & C: Giant covalent structure
- Strong forces between atoms
- Covalent bonding
- N₂, O₂, F₂, Ne: Simple molecular structure
- 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 structure
- Strong attraction between positive ions and delocalised electrons
- Metallic bonding
- Si: Giant covalent structure
- Strong forces between atoms
- Covalent bonding
- P₄, S₈, Cl₂, Ar: Simple molecular structure
- Weak intermolecular forces between molecules
- Covalent bonding within molecules and intermolecular forces between molecules
