Chapter 2 The Material World Molecules Chapter 2 The Material World

Review – Counting Atoms

Counting Atoms When counting atoms in a molecule you must look at: The number of elements present Remember: focus on the upper case letters The subscripts Element Element Ca3(PO4)2 Element Subscript Subscript Subscript

How many atoms are in the following molecule? HCl 2

How many atoms are in the following molecule? H2SO4 7

How many atoms are in the following molecule? Ca(OH)2 Remember: subscripts on the outside of the brackets apply to everything inside (distribute) 5

Representations of the Atom

Bohr-Rutherford Model Draw the Bohr-Rutherford model for Chlorine Cl 17p+ 18n0

Simplified Atomic Model Draw the simplified atomic model of Chlorine Cl 17p+ 18n0 2e- 8e- 7e-

Lewis Dot Model Draw the Lewis dot model of Chlorine Cl

What is a molecule ? A group of atoms connected to one another by a chemical bond. Variety of molecules is virtually limitless How atoms combine to form molecules is determined by: The number of valence electrons (electrons in the outermost shell) The type of atom (metal, non-metal or metalloid)

Particle Model Draw the particle model for water Dalton! H2O

We’ll get back to bonds later Ball and Stick Model Bond! H2O We’ll get back to bonds later