2 Origins of the Idea Democritus (~400 BCE) Matter is composed of atomsAtoms are eternal, invisible, indivisible, and incompressibleGreeks believed in 3 phases or states of matterSolid, liquid, gasWe now add plasma as the fourth phase
3 Matter in the Universe99% of the known matter in the universe is Hydrogen and HeliumThe majority of the known matter is in the form of a plasma in stellar interiorsThe average density of the known matter in the universe is such that 1 gram would occupy a volume 30 x that of EarthThe location and characteristics of most of the matter in the universe is unknown – dark matter
4 AntimatterA matter particle and an antimatter particle are the same with the exception of charge and magnetic properties (which are opposite).Naturally formed and man-made.When matter and antimatter particles collide, they annihilate each other.
5 Elements Fundamental forms of matter Can’t be broken apart by normal means92 occur naturally on EarthThey are the same everywhere
7 What Are Atoms?Smallest particles that retain the distinguishing physical and chemical properties of an elementMade up of subatomic particles:Protons (+)Electrons (-)Neutrons (no charge)
8 Examples of AtomselectronprotonneutronHydrogenHelium
9 Chemical Bonds, Molecules, & Compounds Bond is union between electron structures of atomsAtoms bond to form moleculesMolecules may contain atoms of only one element - O2Molecules of compounds contain more than one element - H2O
10 Atomic Number 6C12 6C13 6C14 Number of protons All atoms of an element have the same atomic numberAtomic number of hydrogen = 1Atomic number of carbon = 6
11 Isotopes vary in mass number 6C12 6C13 6C14Number of protons+Number of neutronsIsotopes vary in mass number
12 IsotopesAtoms of an element with different numbers of neutrons (different mass numbers)Carbon 12 has 6 protons, 6 neutronsCarbon 14 has 6 protons, 8 neutrons6C12 6C13 6C14
13 Chemical OriginsMost chemical elements were created after the Big Bang in subsequent generations of stars.Nucleosynthesis:primordial (H, He, Li)stellar (He -> Fe)explosive (Co -> …)
14 Radioisotopes - Radioactivity Have an unstable nucleus that emits energy and particlesa particles – 2 protons and 2 neutronsb particles – an electrong rays – a high energy photonRadioactive decay transforms radioisotope into a different elementDecay occurs at a fixed rateBecause decay happens at a fixed rate, you can use it for age dating! (C14 has a half-life of 5,700 years.)
15 The Age of the Solar System Ages of rocks can be measured through radioactive dating:Measure abundance of a radioactively decaying element to find the time since formation of the rockDating of rocks on Earth, on the Moon, and meteorites all give ages of ~ 4.6 billion years.