diff --git a/cheatsheets/chemistry cheatsheet.txt b/cheatsheets/chemistry cheatsheet.txt new file mode 100644 index 0000000..599cc45 --- /dev/null +++ b/cheatsheets/chemistry cheatsheet.txt @@ -0,0 +1,110 @@ + + + +atom: + Smallest (about 10^-10 m) unit of matter, forming a specific element. It + consists of: + + - nucleus: Small (about 10000 smaller than atom) but very dense (almost all + atom weight) area containing nucleons, which are: + + - protons: positively charged particles + - neutrons: particles without electric charge + + these are held together by nuclear force that overcomes electric force that + otherwise pushes protons away from each other. + + - electron cloud: Contains electrons (negatively charged particles), that are + attached to protons via electromagnetic force. The cloud is subdivided into + shells (layers), which are subdivided into subshells: + + shell subshells max electrons ^ closer to nucleus + -------------------------------------------- | lower energy + 1 (K) 1s 2 > 2 = 2 | + + 2 (L) 2s 2 \ 2 + 6 = 8 + 2p 6 / + + 3 (M) 3s 2 \ + 3p 6 > 2 + 6 + 10 = 18 + 3d 10 / + + 4 (N) 4s 2 \ + 4p 6 \ ... = 32 + 4d 10 / + 4f 14 / + + 5 (O) 5s 2 \ + 5p 6 \ + 5d 10 > ... = 50 + 5f 14 / + 5g 18 / + ... | + | higher energy + v further from nucleus + + The last (furthest) shell occupied by electrons is called valence shell and + mostly determines chemical properties such as conductivity. Shells are + filled from the innermost, but not generally -- with the higher ones the + rule is more complex (so there can be non-filled non-valence shell). + + Each subshell can further take a form of one of possible orbitals, i.e. + probability "shape" of where the electron can be found. Some subshells, e.g. + 1s or 2s have only one possible orbital (shape) but others, e.g. 2p, have + multiple (2px, 2py, 2pz). + + Atom has the same number of protons and electrons and so has a net electric + charge 0, but can have different number of neutrons, forming different + isotopes. + +electron configuration: Says the specific placement of electrons in (sub)shells. + The lowest energy configuration is called a ground state, e.g. 1s^2 2s^2 2p^6 + 3s^1 for sodium, others are called excited states, e.g. 1s^2 2s^2 2p^6 3p^1. + Transition between configurations consumes or emits energy (photons). + +isotope: Variant of the same atom, differing in number of neutrons (and weight), + e.g. deuterium (helium with 2 neutrons, so called heavy hydrogen). + +ion: Is formed from an atom or molecule that has different number of electrons + than protons, giving it either a positive or negative electric charge (e.g. + after a collision with subatomic particle, radiation etc.). + +molecule: Electrically neutral group of multiple atoms held together by chemical + bond. E.g. O2, H2O etc. + +chemical bond: Lasting bond that holds atoms together. Some types of bonds are: + + - covalent: Atoms share electrons, mostly electron pairs. Atoms want to fill + the valent shell fully, so e.g. H2O is formed by O wanting 2 electrons + (it has 8 electrons total, 2 in first shell, 6 out of 8 possible in the + second valent shell, missing 2) and each O wants 1 (having 1 of 2 possible + in the first shell), so they join to satisfy this. + + + - + + +mole: SI unit of substance amount, means exactly 6.02214076 * 10^23 particles. + +Elements are denoted as: + + Z <--- atomic number, the number of protons, e.g. 1 for hydrogen + E <--- element name, e.g. H for hydrogen + M <--- atomic mass (in grams/mole), e.g. 1.00794 for hydrogen + + +periodic table of elements: + Graphical ordering of elements in 2D table, it consists of: + + - groups: columns, there are 18 groups + - periods: rows, there are 7 periods + + The table shows periodic trends (caused by number of electrons needed to fill + the s, p, d and f subshells, which mostly determines chemical properties), + i.e. repeating patterns, e.g.: + + - metalicity: towards bottom-left corner elements are more metalic + - atomic radius: towards top-right corner elements have bigger atomic radius + - ionization energy: towards top-right elements have more ionization energy + + diff --git a/cheatsheets/words cheatsheet.txt b/cheatsheets/words cheatsheet.txt new file mode 100644 index 0000000..575b8fe --- /dev/null +++ b/cheatsheets/words cheatsheet.txt @@ -0,0 +1,5 @@ +anticlimactic (CS snad "antiklimaktický"): + disappointing after escalating foreshadowing plot (so called climax) + +rustikální: + venkovský, prostý