What is an atom?

1. What is an atom? • Democritus, Greek Philosopher, 400 B.C. Theorized that matter was made up of small indivisible particles, “atomos”. He theorized that these particles were infinite in number, indestructible, and always moving

2. Reeaallyy? • John Dalton, English dude, 1800, theorized that matter atoms of the same element are identical, atoms of different elements can combine, and chemical reactions occur when this happens.

3. Are you cereal? • JJ Thomson, English dude, 1897, found that atoms were not just solid spheres of matter, they had negative charges, he called electrons. His experiment used cathode ray tubes • Robert Milikan, American (Yea baby) shortly after Thomson found the amount of the electrons charge, oil drop experiment

4. Veeerrryyyy interesting. • Eugen Goldstein, discovered that atoms had positive charges • James Chadwick, discovered that atoms had neutrons • Ernest Rutherford, English dude (again), 1911, discovered that atoms had a small dense core of protons and neutrons and were composed mostly of empty space

5. I am so excited. • Neils Bohr, German guy, 1913 developed what is called the “planetary model”, electrons orbit in specific paths around the nucleus. • Louis de Broglie and Erwin Scrhodinger develop the idea that electrons have properties of waves and matter and travel around the nucleus in areas, not paths, called the electron cloud model, also called the quantum mechanical model.

6. Atoms • Proton, + charge, 1 amu • Neutron, 0 charge, 1 amu • Electron, - charge, 0 amu • AMU = atomic mass unit • Smaller units called quarks make up protons and neutrons

7. Atomic Structure • There are 4 main energy levels around an atom where electrons are found. They are divided into sublevels called orbitals, each orbital holds 2 electrons. • S = 1 orbital = 2 electrons • P = 3 orbitals = 6 electrons • D = 5 orbitals = 10 electrons • F = 7 orbitals = 14 electrons

8. Atomic Structure • 1st energy level = s = 2 electrons • 2nd energy level = sp = 8 electrons • 3rd energy level = spd = 18 electrons • 4th energy level = spdf = 32 electrons

9. Orbitals • New, each orbital has a different shape, s orbitals are round, p orbitals look like the figure 8 on the x, y, and z axis. D orbitals look like 2 figure eights on two axis simultaneously, f orbitals relatively complex

10. We thought you wuz a toad! • All elements emit quanta of energy as electrons move from one energy level to another. • When they become excited they move to a higher energy level, and as they cool down the electrons fall back to their ground state emitting energy in the form of light.

11. Do not seek the treasure! • Light is part of the electromagnetic spectrum. This includes Radio waves and radar on the low side and x-rays and gamma on the high side • Amplitude is the height of a wave from rest to crest, it is the energy in the wave. • Wavelength, distance of a complete wave cycle, represented by lambda • Frequency, wave cycles per unit of time, measured in hertz, 1 wave cycle per second

12. That’s my boat! • The wavelength and frequency are inversely proportional to each other. • Light is part of the electromagnetic spectrum, ROYGBIV, red, orange, yellow, green, blue, indigo, and violet, • Red has the lowest frequency and longest wavelength, violet has the highest freq and shortest wavelength.

13. Is that low fat milk you’re drinking? • Atomic spectra is the frequency of light emitted when the electrons in an atom fall back to their ground state, they actually don’t fall back they fall outward. • Each element has an atomic emission spectrum, or specific frequency of light emitted. • The light emitted by an electron has frequency directly proportional to the energy change of the electron

14. No one really knows, it just provocative! • Quanta of light are called photons, they behave as a particle and a wave • This was theorized and proven by Broglie and Schrodinger. • Due to this phenomenon, the position of and electron is never actually known. • Heisenberg uncertainty principle.

15. Atomic Terms • Element, matter made up of all the same atoms • Mass Number, sum of protons and neutrons in the atom • Atomic Number, number of protons, always a whole number • Atomic Mass Number, the average of all the isotopes of an element

16. Atomic Stuff • Four Fundamental Forces that work in an atom. 1.) Electromagnetic Force, keeps electrons around the nucleus 2.) Strong force, holds the nucleus together 3.) Weak Force, radioactivity, 4.) Gravity, responsible for atomic interactions

17. More Atomic Terms!! • Isotope, atoms of the same element with a different number of neutrons, usually radioactive. • Substance, matter that has the same properties throughout, could be an element or compound. • Compound, substance made up of two or more elements. Formulas are used to represent compounds, H2O, CO2

18. Periodic Table • Created by Dimitri Mendeleev, Russian, 1869, he organized atoms according to their atomic weight • Henry Moseley, British, 1914, rearranged the table by atomic number, currently used today. • Groups or families, each vertical column, they have similar properties and the same number of valence or outer electrons

19. More !?!? • Periods or rows, horizontal rows in the table, each row has the same number of energy levels • Each chemical is represented by the first or first two letters in the elements name, the first letter is always capitalized. • Alkali Metals, 1st column, very reactive metals • Alkali Earth Metals, 2nd Column, not quite as reactive metals

20. More and More!?!? • Transition Elements, columns 3-12, typical metals, iron, copper, etc. • Metals, all the elements to the left of the metalloids, conduct heat & electricity, shiny, malleable (beaten and formed), ductile (drawn into wires) • Metalloids, diagonal column of elements between metals and nonmetals, they have metallic and nonmetallic properties

21. Still more • Halogens, second to last column of elements, group 17, very reactive gases, halogen means “salt former” reacts with metals to form salts • Noble Gases, last column, unreactive, inert gases • Nonmetals, all elements to the right of the metalloids, do not conduce heat or electricity, dull, brittle, powdery.

22. The end • Rare Earth Elements, two separate rows at the bottom of the table, called lanthanides and actinides, all the actinides are radioactive.