Atomic Concepts Review Sheet
Protons Mass= 1amu Charge +1
Neutrons Mass=1amu Charge 0
Electrons Mass=0 Charge –1
Nucleons (in nucleus) are protons and neutrons
Electrons revolve around nucleus
Ernest Rutherford’s Gold Foil experiment demonstrated atom mostly empty space, and
that the nucleus was small, dense, and positively charged
Atomic number equals the number of protons
Mass number equals protons plus neutrons
Mass number – atomic number (protons) = neutrons
Isotopes have same atomic number (same element) but different number of neutrons
(different atomic mass numbers)
14
An isotope can be represented in three ways ex. C-14 or Carbon-14 or 6C
Atomic mass is a weighted average of all naturally occurring isotopes
To calculate multiply the mass by the percentage as a decimal and add up
The number of electrons is equal to the number of protons in an atom
Electrons occupy energy levels in an atom. The further an electron is from the nucleus
the more energy it has
Energy level 1 or n=1 the closest to the nucleus, can hold a maximum of 2 electrons
Energy levels 2,3, and 4 will hold 8, 18, and 32 maximum
As an electron gains energy it can move to a higher energy level and the atom is in the
excited state.
To see if an atom is in an excited state see if it is possible for an electron to move down
Ex. 2-7-1 is in the excited state.
The electron in the excited state will spontaneously return to the ground state giving of
energy in the form of light.
This can be measured using a spectrometer and be used to identify the element
Valence electrons are the electrons in the outermost shell
The electron cloud theory says that an orbital is an area of most probable location of an
electron
Ions are charged particles. + ions have lost electrons – ions have gained electrons
To calculate electrons take atomic number and either add or substract electrons
Pure substances are elements or compounds
All elements are found on the periodic table
Elements can not be broken down chemically compounds can
Binary compounds contain 2 elements Ternary contain 3
Mixtures contain two or more elements or compounds combined physically
They can be separated physically.
Homogenous mixtures (like solutions) are uniform
Heterogenous mixtures are not uniform.