ATOMS

Phet Simulation: Build an Atom What particle determines what element you have? What particle(s) can change without changing the identity of an element? What particle determines whether or not an element is an ion?

Atoms: the building blocks of matter? Never trust an Atom! They make up everything! Image via ThinkGeeks

An atom is the smallest unit of an element that is possible. All the matter around us is made of individual atoms. Sometimes different atoms join together to form new substances. Two Hydrogen Atoms will join an Oxygen atom and form water (H2O). O H H Molecule: consists of individual atoms in fixed proportions. In this sense atoms are the building blocks of matter but atoms are usually made up of three smaller particles and two of those particles are made up of even smaller particles. So an atom is not a fundamental building block of matter.

Protons, Neutrons and Electrons Positively charged (+1). Found in the nucleus. Defines what an atom is. Neutral particle in an atom. Found in the nucleus. Required for stability. Negatively charged particle (-1). Found outside the nucleus. Main cause of Chemical Bonding.

Protons, Neutrons and Electrons Protons and Neutrons are roughly equal in mass but a neutron is ever so slightly bigger than a proton. A proton (and a neutron) are about 1800 times as massive as an electron. A proton and electron would NEVER balance!

Protons, Neutrons and Electrons Protons and Neutrons are roughly equal in mass but a neutron is ever so slightly bigger than a proton. A proton (and a neutron) are about 1800 times as massive as an electron.

Protons, Neutrons and Electrons Protons and Neutrons are roughly equal in mass but a neutron is ever so slightly bigger than a proton. A proton (and a neutron) are about 1800 times as massive as an electron. It would take 1800 Electrons to balance with 1 Proton or Neutron!

Model of a Helium Atom A typical Helium atom 2 Protons 2 Neutrons 2 Electrons Nucleus: Dense central region in an atom where neutrons and protons are found. Contains most of the mass of an atom. Image Captured From Phet Physics Simulation

The Periodic Table Fe Atomic Number Average Atomic Mass 26 IRON 55.85 The number of protons in the nucleus of the atom Average Atomic Mass The total number of protons AND neutrons in the atom’s nucleus The Periodic Table

C 6 6 6 Protons:_______ Neutrons:______ Electrons:_____ 6 CARBON 12.01 A neutral carbon atom has how many of each particle? Protons:_______ Neutrons:______ Electrons:_____ 6 6 6 The 6 on the top is the atomic number of carbon and that is also the number of protons any atom of carbon must have. The 12.01 on the bottom is the average atomic mass and is also the number of protons and neutrons in average carbon atom. Six of those 12 must be protons because Carbon has an atomic number of 6 so what is left over are neutrons. An electrically neutral must have an overall charge of 0. This means the total number of electrons (-1 charge) must be equal to the number of protons (+1 charge).

O 8 8 8 +8 -8 Protons:_______ Neutrons:______ Electrons:_____ +1 +1 +1 Oxygen 16 8 8 8 +1 +1 +1 +1 +1 +1 +1 +8 +1 -8 -1 -1 -1 -1 -1 -1 -1 -1

Ne Protons:_______ Neutrons:______ Electrons:_____ 10 NEON 20.18 Proton Number = Atomic Number. Neutron Number: Atomic Mass (rounded) minus Atomic Number. (or bottom minus top) Electron Number = Proton Number (if Neutral) 10 Ne NEON 20.18 Protons:_______ Neutrons:______ Electrons:_____

Why do we only consider the number of neutrons and protons when determining the average atomic mass of an atom? CONCEPT CHECK ANSWER: Electrons are much lighter than protons and neutrons so we can ignore them.

Data Table 1 Element Name Element Symbol Atomic Number Atomic Mass Electron Number Proton Number Neutron Number Hydrogen Oxygen Neon Carbon Nitrogen Build these atoms using the phet physics simulation. Neatly draw them using the same color scheme that the app uses. Element Name Element Symbol Atomic Number Atomic Mass Electron Number Proton Number Neutron Number He 6 11 35 61

Just How Small is an Atom? (vid) How many copper atoms lined up side by side would equal a line 1cm in length? Atoms will NEVER be seen optically since atoms are smaller than the wavelength of visible light. Are you sitting in your chairs? 100,000,000 neutron mass 1.674927211 x10-27kg proton mass 1.672621637 x10-27 kg neutron-proton mass ratio 1.00137841918 electron charge -1.602176487 x 10-19c  Proton charge +1.602176487 x 10-19c  electron mass 9.1 x 10-31 kg Scientific Notation!

“Atoms are so tiny that I inhale billions of trillions with each breath, nearly a trillion times more atoms than the total population of people since time zero! In each breath, I inhale billions of atoms exhaled by every person who ever lived, excepting newborn babies far away. But atoms I’ve recycled are now part of them. From a physics point of view, we’re all one . . . There are about as many atoms of air in your lungs at any moment as there are breathfuls of air in the atmosphere of the whole world. (There are about 10^22 atoms in a liter of air at atmospheric pressure, and about 10^22 liters of air in the atmosphere.) When you exhale a single breath of air, in about 6 years that breath becomes evenly mixed in the atmosphere. Then, every person in the world that inhales a breath of air gets, on average, one of the many atoms you exhaled in that single breath! And this occurs for each breath you exhale! Considering the many thousands of breaths that people exhale, at any moment you have hordes of atoms in your lungs that were once in the lungs of every person who ever lived. We are literally breathing one another.” (Hewitt, Conceptual Physics, 8th. Ed –pg 180)