C3 - structure + bonding Flashcards
Why don’t substances change temperature when changing state
The thermal energy is used to break the bonds
What structure do ionic compounds have
Giant lattice
When can ionic compounds conduct electricity
When in solution or when melted
What is the rule for melting point for ionic compounds
The smaller the ion and the higher it’s charge, the higher the electrostatic forces of attraction are so the higher the melting point
How are covalent bonds formed
Due to the strong electrostatic forces between the positively charged nucleus of the atom and the bonding pair of electrons which are shared between the atoms
What 2 types of structure can covalent molecules have and their properties
Simple covalent - small number of atoms, non metals, low boiling points because strong bonds between atoms but weak intermolecular forces, can’t conduct electricity
Giant covalent - high melting + boiling points due to strong bonds between atoms, aren’t soluble, don’t conduct
What are allotropes
Covalent structures made of the same atoms with different numbers of bonds (diamond and graphite)
Properties of diamond and graphite
Diamond - hard, high melting point, doesn’t conduct, 4 bonds per atom
Graphite - soft, high melting point, conducts, 3 bonds per atom, layers
What is metallic bonding
The very strong attraction between the metal cations and and the delocalised valence electrons
Why do metals have high boiling points
A lot of energy is needed to break the metallic bonds
What is an alloy
A mixture of two or more elements where at least one is a metal
Why are alloys stronger that metals
The different sized atoms disrupts the lattice, which decreases conductivity but means that the layers can’t slide past each other so it isn’t malleable
What are nano particles and why
Particles between 1 and 100 Nm - invisible in light, high SA:V
What is graphene
A single layer of graphite 1 atom thick
