Download Regents Chemistry Review

6
Atomic Concepts
Subatomic Particles
Charge
Mass
proton + 1
1 amu
electron – 1
1/1836
neutron
0
1
Location
atomic mass number (#p + #n)
nucleus
orbits
nucleus
atomic number
12.011
C
(#p)
6p+ 6e
---------------------------------------------------◦
(#n)
6n
NOTE: charge of nucleus = #p
Isotopes – atoms of the same element, which differ in the number of neutrons; have the same
atomic no., but a different mass number
12.0000
13.0335
C
6p+ 6e
-
-------------------◦
6n
WEIGHTED AVERAGE ATOMIC MASS
C
6p+ 6e
-
0.9889 (12.000) + 0.0111(13.0335) = 12.011 amu
The atomic mass will be closest to the isotope with the
greatest percentage.
-----------------◦
7n
relative abundance:
98.89%
-
1.11%
Electron Configuration – the arrangement of electrons in the energy levels
(orbits, shells) of an atom in the ground state.
___________ distance from nucleus, ___________ energy of electron
In the ground state, electrons fill the lowest available energy level, starting from
the shell closest to the nucleus.
Complete Energy Levels:
2-8-18-32 …. 8 max “valence” e----------------------------------------------------------------------------------------------------------------------------
7
“Ground State”
Possible “Excited State”- move only one e further away from
-
nucleus
2-8-3
2-7-4
or 2-8-2-1 or 1-8-4 , but not 3-7-3
Metals- lose electrons forming (+) ions
Na
2-8-1
Na +1
2-8
Nonmetals – gain electrons forming (-) ions
O-2
O
2-6
2-8
The ions have a “Noble Gas” electron configuration = 8 electrons in the outermost shell.
Lewis (e- Dot) Structure – represents only the valence electrons; start with the first 2 dots
together in the 12 o’clock position, continue placing electrons in the remaining positions (3, 6 &
9 o’clock), one at a time, until you have two in each; the max is an OCTET.
Rutherford’s Gold Foil Experiment
An atom is mostly “empty” space;
its “nucleus” is very small, but massive,
and it’s positively charged.
Wave Mechanical Model
for explaining spectra of elements with
multi-electron atoms
Orbital – the region around the nucleus of an
atom where an electron can most probably be
found; aka “electron cloud”.