Democritus Pneumonic Device Democritus’ Atomos No Slice 440 BC (2,500 years ago) Hypothesis ALL matter is made of particles too small to be seen, that cannot be split into smaller parts “Atomos” meaning “cannot be cut” Atomic Model Sugar is made of “sugar atomos” Rocks are made of “rock atomos” Copper is made of “copper atomos”

John Dalton 1803 Experiment Hypothesis Measured masses of elements and compounds during chemical reactions Hypothesis All elements are made of atoms All atoms of the same element are IDENTICAL Compounds contain atoms of more than one element The same compounds always combine the same way

Dalton’s Atomic Model Tiny, solid, indestructible particles “Bowling Ball Theory” Pneumonic Device Dalton’s Atomic Bowling Balls Solid Compounds And Bowling Balls Of John Dalton

J.J. Thomson 1897 Experiment Hypothesis Shot lasers between two magnets ( + & -). Laser bent towards the positive magnet. Hypothesis Atoms made of smaller particles Atoms have a neutral charge Atoms are positively charged “blob” of matter, with little negative charges scattered throughout.

J.J. Thomson’s Atomic Model Tiny solid sphere (like Dalton) but with negative charges scattered throughout “Plum Pudding” Think of mint-chocolate chip ice cream Pneumonic Device Thomson’s Unique Plum Pudding And Charges

Ernest Rutherford 1911 Experiment Hypothesis Shot alpha particles (+ charge) at gold foil. The particles bounced off in crazy (unpredicted) directions Hypothesis Atoms have very small, positively charged nucleus Nucleus surrounded by negative charges orbiting nucleus Atoms are mostly empty space

Rutherford's Atomic Model “Planetary Model” Negatively charged electrons orbit positively charged nucleus Mostly empty space Pneumonic Device

Neils Bohr 1913 Experiment Hypothesis None! Just a super smart dude. Electrons orbit the nucleus at fixed distances. Each distance is an energy level. Electrons gain or lose energy as they move between energy levels.

- - - - - - - Bohr’s Atomic Model “Bohr Model” Most commonly used in chemistry and chemistry classes Pneumonic Device - - - - - -

Erwin Schrödinger 1926 Experiment Hypothesis None! Just a super smart dude. Hypothesis Electrons orbit the nucleus in a sort of “cloud” “Cloud” describes where electrons probably are

Schrödinger’s Atomic Model “Electron Cloud Model” Most accurate model of the atom Difficult to use for science problems Pneumonic Device

Let’s make a timeline! With a partner, get a piece of large construction paper from the front of the room. NEATLY divide the paper into SIX sections Using the colored pencils provided (use lots of color!) to draw colored pictures of the evolution of the atomic model. ABOVE each picture of each model, you must write the name of the scientist who developed the model, the year that they developed it, and important information about what they added to their model and why it is important. You will be graded on NEATNESS, CREATIVITY, ACCURACY, and EFFORT.

Here is a sample… 440 “Atomos” There is a limit to how small you can make particles “Bowling Ball Theory” Atoms and mix to make compounds “Plum Pudding” Atoms are positive with negative charges mixed throughout

Ch. 4/5 Notes Day 3 1/28/16

ATOMS!!!! Particle Symbol Relative Charge Electron e- negative In the Nucleus… Proton p+ Positive Neutron n Neutral n p+ e- Protons and neutrons take up most of the mass of an atom. The rest is mostly empty space!

All of this information is in the Periodic Table Element Name Atomic Number – the number of protons that are in the nucleus of one atom of an element. **Also equal to the number of electrons in the element. Chemical Symbol Atomic Mass – the SUM of the number of protons and neutrons that are in the nucleus of one atom of an element.

Let’s Practice… Element Name Chemical Symbol # of Protons Element Name # of Electrons # of Neutrons Element Name Chemical Symbol # of Protons # of Electrons # of Neutrons

Maximum number of electrons Energy Level Maximum number of electrons 1 2 8 3 18 4 32

Draw the following atoms of the elements in your learning log! Give the atomic #, Atomic Symbol, Atomic mass and number of protons, neutrons and electrons for each element. Use three different colors to represent the neutrons, protons and electrons. Oxygen Carbon Chlorine Hydrogen Argon 1 atom of your choice

Isotope An element that has the SAME number of protons (atomic #) but DIFFERENT number of neutrons. Elements with the SAME number of protons are the SAME element. **The atomic Mass on the periodic table is the most common mass of that element. You could think of it as the “average weight” of an element.

Example All Oxygen atoms have 8 protons, but can have different numbers of neutrons 16.999 17.999

Because scientists are ridiculous… Here is another important way to write atomic number and atomic mass B 11 Atomic Number 5 Atomic Mass

Which of the following “unknown” elements are isotopes of Platinum 194 78 194 77 196 78

Which of the following “unknown” elements are isotopes of Tin 120 50 116 50 117 51

Which of the following “unknown” elements are isotopes of Antimony 120 50 121 50 123 51