Maths for A Level Chemistry - updated edition

5.2 3D shapes 3D shapes cannot be represented accurately on a ϐlat surface. Many molecules have 3D structures and it is important to be able to imagine how they look in 3D and to be able to draw a diagram to show the structure. Cube (8 vertices and 6 faces) Tetrahedron (triangular-based pyramid) (4 vertices and 4 faces) Pyramid (square-based pyramid) (5 vertices and 5 faces) Trigonal bi-pyramid (5 vertices and 6 faces) Octahedron (6 vertices and 8 faces) 5.3 Angles There are a number of angle rules which will help you understand about bond angles and they are described here. Angles on a straight line a + b = 180° a b The angles on a straight line add up to 180 o . Pointer Note that the vertices are the corners and the faces are the flat sides. 5 Geometry 47