1. Note Guide 1-1 Science and Studying Atoms What is science?What is science --Science begins as curiosity and tries to end with discovery. -- system of knowledge and the methods used to find that knowledge. -- scientists use models to help bring things into perspective and to make it easier to understand. --scientists use a systematic method (scientific method) to try and discover the answers to their curiosity. --steps include observations, forming hypothesis, testing the hypothesis, analyzing and drawing conclusions. keep in mind, one test does not make a theory AND parts, predictions and ideas of the experiment can be revised

2. --scientists also communicate in the same language (SI). this is a system of measurement similar to metrics. EX: We use things like inches and they use things like centimeters….BUT WE ALL IN SCIENCE USE THE SAME (centimeters, for example) Atoms --get origin from greek scientist Democritis, who says they are indivisible. Dalton = Early Scientist = matter is made up of individual particles called atoms (too small to study to observe) --these atoms have no electrical charge neutral Next, Thomson through experiments, provides first evidence that atoms are made of smaller particlesThomson

3. --thomsons experiment (see pg. 103) showed the presence of negatively charged particles Next, Rutherford = gold foil experiment (see pg 104)Rutherford --aims a narrow beam of alpha particles at a thin piece of gold foil. --using a screen around the gold, rutherford was hoping to be able to follow the path an alpha particle takes after it passes through the gold. --Particles did not behave like he thought: some went straight through, some bounced off at weird angles, while some came straight back. RESULT: rutherford suggests the nucleus, where positive charges hang out.

4. Atoms made of 3 main parts* PartsSymbolAMUCharge Electrone-e- About 0 - Proton*p+p+ 1+ Neutron*n0n0 10 **mass of an atom mostly in the nucleus Note Guide 1-2 The structure of an atomstructure of an atom

5. Atomic number = # of p + in an element. Atoms of any given element has same # of p +Atomic number i.e. Hydrogen (H) has 1 proton = Atomic number is 1 Mass number = tells how many p + and n 0 there are in an atom i.e. Al = Aluminum p + = (13)n 0 = (14) = mass number is (27) --Protons + neutrons = mass number Isotopes – atoms of the same element that have different #s of neutrons, thus different mass numbers.Isotopes

6. --isotopes do have the same atomic # --Why? # of protons stay the same --mass # different because # of neutrons different. EX: Oxygen (O) – 8 protons (never changes!) --some oxygens have 9 neutrons, giving a mass # of 17. --naming isotopes = using the element name and mass number (Oxygen – 17) --when an element has a number after it, we are talking about an isotope.