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Notes on Khan Academy Chemistry

History of Chemistry

Atom, Element, Periodic Table, Ion, Isotope Periodic Table of Elements

Molecule, Bond, Formula, Nomenclature

Chemical Reactions, Equations

Types of chemical reactions:

Acid, Base, Salt

Heat, Cooking

Radiation, Explosives

Electrochemical Reactions

Atom

Element

Molecule - bonds

Compound - bonds

Mixture - no bonds ?

Bonds

Characteristics of Elements

solid, liquid, gas

Heavy Metals Precious Metals Nutritional Metals Poisons Silly Symbols Date Discovered, historicity, alchemy Named after people Named after planets Named after places Silly names: Unobtanium Radioactive Elements

Atomic Structure, shells, traits, bonds, reactions YouTube:AtomicSchool playlist https://www.youtube.com/playlist?list=PLYbDrmR0pxgrTmNsqqSXC-6xrJIkCjpfo

acid = molecule or ion capable of:

• donating a proton
• making a covalent bond with an electron pair

electrons

electro-negativity

how energy is released or required when an electron changes state

shell = energy level

outer shells have higher energy level ?

shells subshells and orbitals

Electrons closer to the nucleus have a higher binding energy. They are bound more tightly to the nucleus. It takes more energy to knock them away from the nucleus.

Salman Khan: Introduction to photoelectron spectroscopy

Atoms are bombarded with XRay photons which knock the electrons away from the nucleus onto a detector. The detector then gives us a map of the binding energy of the electrons. The photoelectron spectrum. Electrons from the outer shell fly the farthest because they have the lowest binding energy.

Salman Khan: Valence electrons

Knowing the configuration of electrons in an atom gives us clues as to how that atom will react to other atoms.

• is it reactive or inert?
• will it dissolve in water? hydrophobia, hydrophillic (attraction, repulsion)
• is it electronegative
• does it conduct electricity
• does it have polarity
• does it have a charge? neutral, positive, or negative
• is it radioactive?
• at what temperature does it convert from solid to liquid to gas?

Salman Khan: Atomic radius trends on periodic table

Coulomb attraction: between nucleus and electrons.

Atoms get smaller trending to the right on the periodic table. Because the larger number of protons creates a stronger positive charge in the nucleus and the larger number of valence electrons creates a stronger negative charge in the outer shell. So these stronger charges pull the electron shells in closer to the nucleus.

So krypton is smaller than potassium. It has more protons and electrons, so you might think it would be bigger. But it is smaller because of the increased charge.

Helium is the smallest atom. Smaller than hydrogen.

The radius increases down and to the right across the periodic table. Down, because each additional shell is farther away from the nucleus. To the right, because the charge between the nucleus and the outer shell increases.

Analyze a mixture. What chemicals are there by mass?

isotopes

atomic mass for each element

Sal Khan working math problems.

1. NaCl plus contaminates.

https://www.khanacademy.org/science/chemistry/x822131fc:more-about-mixtures/x822131fc:mixtures/v/worked-example-analyzing-purity-of-a-mixture?modal=1

sodium chloride NaCl

sodium iodide NaI

potassium chloride KCl

lithium chloride LiCl

Na Cl I K Li

2. Potassium supplement as KCl, g per mol, mass, mol, molar mass

https://www.khanacademy.org/science/chemistry/x822131fc:more-about-mixtures/x822131fc:mixtures/v/worked-example-calculating-mass-of-substance-in-mixture?modal=1

Sal Khan: Isotopes and mass spectrometry

https://www.khanacademy.org/science/chemistry/x822131fc:untitled-537/mass-spectrometry/v/mass-spectrometry?modal=1

how spectrometry is used to detect and measure the amounts of isotope in a sample

using zirconium Zr as an example

Sal Khan: Identifying an element from its mass spectrum

https://www.khanacademy.org/science/chemistry/x822131fc:untitled-537/mass-spectrometry/v/worked-example-identifying-element-from-mass-spectrum?modal=1

using strontium Sr as an example

Wikipedia: “Chemistry”, https://en.wikipedia.org/wiki/Chemistry, Retrieved 23-Mar-2019.

Khan Academy: “Chemistry”, https://www.khanacademy.org/science/chemistry, Retrieved 23-Mar-2019. Notes

Primrose Kitten: “The whole of ATOMIC STRUCTURE in 20 minutes!”, https://www.youtube.com/watch?v=sYlmoNKypoY, Retrieved 23-Mar-2019. Notes

Crash Course: “The History of Atomic Chemistry”,https://www.youtube.com/watch?v=thnDxFdkzZs, Retrieved 23-Mar-2019. Notes

NIH: PubChem (open chemistry database) https://pubchem.ncbi.nlm.nih.gov/

Professor Dave Explains: “General Chemistry”, https://youtube.com/playlist?list=PLybg94GvOJ9EbbO2RXPWTUNIIE0C7hSfm