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cheatsheets/chemistry cheatsheet.txt

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+
+
+
+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
+
+

cheatsheets/words cheatsheet.txt

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+anticlimactic (CS snad "antiklimaktický"):
+  disappointing after escalating foreshadowing plot (so called climax)
+
+rustikální:
+  venkovský, prostý