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