the principle that chemical properties of the elements are periodic functions of their atomic numbers
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groups or families
vertical columns
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periods
horizontal rows
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octet rule
the tendency to acquire a total of 8 valence electrons
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isoelectronic
having the same numbers of electrons or the same electronic structure.
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ion
a particle that is electrically charged; an atom or molecule or group that has lost or gained one or more electrons
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metals
typically cations - positively charged
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non-metals
typically anions - negatively charged
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multivalent ions
usually transition metals may form ions with more than one charge
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polyatomic ion
a group of atoms covalently bonded that carry a charge
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alkali metals
group 1
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halogens
group 17
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noble gases
group 18
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isotope
one of two or more atoms with the same atomic number but with different numbers of neutrons
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average atomic mass
average mass of several items. Weighted average.
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radioisotope
Some isotopes of atoms are very unstable. A radioactive isotope of an element; is produced either naturally or artificially.
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problems in rutherfords model
why the protons in the nucleus didn’t repel each other
why the electrons in orbit didn’t spiral into the nucleus
the unique line spectra of elements
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energy levels
Each orbit is called an energy level since it has a specific amount (quanta) of energy associated with it Normally, electrons that exist in those energy levels are if an electron absorbs additional energy, then it can be “promoted” from a lower energy state to a higher energy state and is then in an unstable state - EXCITED STATE
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Staircase idea
when the electron “falls” back to its original ground state it releases energy in the form of light
different sized “falls” = different amounts of energy released = different colours in the spectrum = a “fingerprint” of the element’s unique electron arrangement
SMALL jumps down = less energy released (lower energy ~ lower frequency ~ longer ) = toward red end of the spectrum LARGE jumps down = more energy (higher energy ~ higher frequency~ shorter λ) = toward violet end of spectrum
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OVERCOMING the ISSUES of RUTHERFORD’S MODEL
The existence of a “strong nuclear force” , which is greater than the electrostatic force of repulsion Electrons are stable since they are quantized Each element has its own particular, organized electron arrangement, therefore its own unique emissions spectrum
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new, highly mathematical atomic model
Quantum Mechanical Model
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Quantum Mechanical Model and Energy:
Electrons occupy specific energy levels/shells in an atom. The number of electrons in each level is governed by the formula 2n2. Schrodinger proposed that the atom was arranged as “layers within layers” in terms of the electron shells. Schrodinger also proposed that an electron behaves in a waves manner rather than just as particles. Thus, electrons are both particles and waves at the same time. Since electrons are waves, they do no remain localized in a 2-D orbit. Instead of being organized in 2-D orbits, electrons are actually found in 3-D orbitals. Each orbital defines an area where the probability of finding an electron is high. These orbitals are known as electron clouds.
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orbits
2d path
fixed distance from nucleas
circular or elliptical path
2n2 electrons per orbit
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orbitals
3d path
variable distance from nucleus
no path; varied shape of region
2 electrons per orbital
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orbital sublevels
“s” “p” “d” “f”
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s
Spherical s orbital 2
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p
Perpendicular p orbital 6
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d
Diffuse d orbital 10
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f
Fundamental f orbital 14
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Pauli Exclusion Principle
each orbital can hold 2 electrons with opposite spins “opposite direction rule”
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Aufbau Principle
electrons fill the lowest energy orbitals first “lazy tenant rule”
start at the top and add electrons in the order shown by the diagonal arrows this is known as “Order or Filling”
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