Note Guide 1-1 Science and Studying Atoms

•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

--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 particles

--thomson’s experiment (see pg. 103) showed the presence of negatively charged particles

•Next, Rutherford = gold foil experiment (see pg 104)

--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.

•Atoms made of 3 main parts*

Parts Symbol AMU Charge

Electron e- About 0 -Proton* p+ 1 +

Neutron* n0 1 0

**mass of an atom mostly in the nucleus

Note Guide 1-2 The structure of an atom

•Atomic number = # of p+ in an element. Atoms of any given element has same # of p+

i.e. Hydrogen (H) has 1 proton = Atomic number is 1

•Mass number = tells how many p+ and n0 there are in an atom

i.e. Al = Aluminum

p+ = (13) n0 = (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 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.