· Chemistry - Atoms
- First there were electrons,
protons and neutrons freely flyng around the world.
- In some cases electron and
proton would fly close to each other, and if their relative speed and angle
would be right,
force would force the electron to start circling/orbiting around the proton.
- This process is very similar
to planets orbiting the sun or satelites oribiting planets with the difference
that electron and
are attracted with electrical force and planets are attracted with
- This electron and proton
will now contine to fly around the world in this newly created structure called
- Such simple atom would
eventualy hit other electrons, protons and neutrons resulting in more complex
- In the center of each atom
is nucleus consistent of protons and optional neutrons.
- Electrons circle around
- Number of electrons is
always equal to the number of protons.
- Neutrons are not electricly
charged and it is possible that nucleus has no neutrons.
- Atom is also called chemical
- Each atom is distinguished
by its atomic number, which is the number of protons in its nucleus.
- Atoms are specified like
- The bottom number represents
the atomic number and it is the number of protons in nucleus.
- The top number represents
the mass number and it is number of protons and neutrons in nucleus.
- The fact that there are no
plus or minus signs anywhere means that number of electrons is equal to number
table of chemical elements:
- There are 117 types of atoms
known in the world.
- They are all listed in the
Periodic table of chemical elements.
- An electron shell may be
thought of as an orbit followed by electrons around nucleus.
- Eeach orbit can contain only
a fixed number of electrons
- All electrons in the same
orbit have the same kinetic energy.
- Each orbit has different
radius around nucleus
- Orbit must fill completely
before electrons can be added to an outer orbit.
- Electron shells are labelled
(K, L, M, N, O, P, Q) or (1, 2, 3, 4, 5, 6, 7) going from innermost shell
- Electrons in outer shells
have higher average energy and travel further from the nucleus than those in
- This makes them more
important in determining how the atom reacts chemically and behaves as a
of the atom's nucleus upon them is weaker and more easily broken.
- Valence shell is the outer
shell, that is the last outward shell that contains atoms.
- Atoms like to have full
valence shells which motivates them to share atoms through covalent bonds.
- Each shell can have 2n2
electrons where n is the number of the shell which results in following table:
Max number of electrons
2×12 = 2
2×22 = 8
2×32 = 18
2×42 = 32
2×52 = 50