Periodicity and Periodic Trends Flashcards
How are elements arranged in the new periodic table? (2)
- Physical and chemical properties
- Atomic number
What is periodicity?
A repeating trend in properties of the elements across a period
What are some properties that change across a period? (4)
- Electron configuration
- Ionisation energy
- Structure
- Melting points
What is the first ionisation energy?
The energy required to remove one electron from each atom in one mole of gaseous atoms of an element to form one mole of gaseous 1+ ions
How does atomic radius affect ionisation energy?
As atomic radius increases, there is less attraction between the nucleus an the outer electrons. Ionisation energy decreases
How does nuclear charge affect ionisation energy?
Greater the nuclear charge, the greater attraction between the nucleus and the outer electrons. Ionisation energy increases
How does electron shielding affect ionisation energy?
More shielding means more repulsion between electrons and reduced attraction of nucleus to outermost electrons. Ionisation energy decreases
What is the trend as you go down a group? (4)
- Atomic radius increases
- Electron shielding increases (more electrons)
- Nuclear attraction to outer electrons decreases
- First ionisation energy decreases
What is the trend as you go down a period? (5)
- Nuclear charge increases
- Similar shielding (same shell)
- Nuclear attraction increases
- Atomic radius decreases
- First ionisation energy increases
Why is there a drop in ionisation energy from nitrogen to oxygen? (3)
- In nitrogen and oxygen the highest energy electrons are in the 2p sub-shell
- In oxygen, the paired electrons repel each other making it easier to remove
- In nitrogen the electrons are as far apart as possible
What is metallic bonding?
The strong electrostatic attraction between cations (positive ions) and delocalised electrons
What is the structure of metals? (3)
- Cations in fixed places
- Electrons are delocalised and free to move
- Giant metallic lattice
Why are the properties of metals? (3)
- Strong metallic bonds
- High electrical conductivity
- High melting and boiling points
Why can metals conduct electricity? (3)
- Can conduct in both solid and liquid state
- Contain delocalised electrons that can move through the structure
- Electrons carry the charge across the metal
Why do metals have high melting and boiling points? (2)
- High temperatures necessary to provide large amount of energy needed to overcome the strong electrostatic attraction between cations and anions
- Strong attraction means more energy needed
Are metals soluble?
No, they just react with solvents
What is a giant covalent lattice?
Many atoms being held together by a network of strong covalent bonds
What are the properties of giant covalent lattices? (
- High MP/BP - Strong covalent bonds require high temps. to provide enough energy to break
- Insoluble - covalent bonds are too strong to be broken by interactions with solvents
- Do not conduct electricity (EXCEPT Graphite and Graphene) - no available electrons to carry the charge across the molecule
What is the structure of graphite? (2)
- Hexagonally arranged carbon atoms
- Parallel layers held together by weak London forces
What is the structure of graphene? (2)
- Single layer of graphite
- Hexagonally arranged carbon atoms
Why can graphite and graphene conduct electricity? (3)
- The bonding only uses three out of four electrons on the carbon
- One free electron left
- Free electron is free to move across the molecule and carry the charge
Why is there a sharp decrease in the periodic trend in melting points?
Point marks a change between giant to simple molecular structures
What elements form giant metallic structures? (5)
- Li
- Be
- Na
- Mg
- Al
What elements form giant covalent structures? (3)
- B
- C
- Si
