Matter and Atomic Structure Chapter 2

What Are Elements?

Elements All matter is made of elements Element - a substance that cannot be broken down into simpler substances by physical or chemical means What are some examples? Gold How many are there? 92 naturally occuring

Elements Identified with 1, 2, or 3 letter symbols Examples: Oxygen - O Sodium - Na Unununium - Uuu

Elements are Made of Atoms Each element has its own characteristics. Atom - smallest particle of an element that has all the characteristics of that element

Elements are Made of Atoms Atoms consist of a nucleus with: Protons - (p+); has mass and a positive electrical charge Neutrons (n0); same mass as a proton and NO electrical charge Surrounding atoms are: Electrons - (e-); has little mass and a negative charge

Atomic Number Atomic Number - The number of protons in an atom’s nucleus Oxygen has 8 protons, so its atomic number is 8 Carbon has 6 protons, what’s the atomic number? Molybdenum’s atomic number is 42, how many protons?

Atomic Mass Atomic Mass - protons + neutrons Uranium - 92 protons and 146 neutrons Mass number = 92 + 146 = 238 Silver (Ag) has an atomic mass of 107 and an atomic number of 47. How many neutrons does it have? 60