Review Stuff for Structure of an atom
Structure of an atom
 Smallest unit of matter that can exist while still retaining the properties
 Consists of two different parts
o Nucleus
 Located in the center of the atom
 Contains all of the mass of an atom
 Contains Protons and Neutrons
 Protons
o They are positively charged (+) p+
o Number of protons never change (it is like DNA)
o # of protons = the atomic # of an element
o # of protons = the #of electrons
 An atom should have an overall neutral charge.
Therefore the positive particles must be equal to
the negative particles
o Protons contribute to the atomic mass
 Neutrons
o Neutrons have no charge, they are neutral (n0)
o To find neutrons, mass # - protons = neutrons
o Neutrons can change based on the existing isotope of
that elements
o Neutrons contribute to the mass # of the element
 Protons + neutrons= mass #
o Outer Shell/ Electron Cloud
 Electron orbitals represent energy levels. The outermost shell has the
highest energy level
 Electrons are located in the electron shells
o Electrons have a negative charge (-) (e-)
o They move around rapidly in their electron clouds
o Electrons do not have mass they just take up space
o #of electrons = #protons
 Periodic Table
o Groups- The columns on the periodic table are called GROUPS
 There are 8 groups on the periodic table
 The Group# is equal to the # of valence electrons in an atom (v.e-)
 Valence Electrons are the electrons used for bonding
 The max number of valence electrons that an atom can have is
8. This is because there are only 8 groups on the periodic table
 Valence electrons are located in the outer most shell (furthest
from the nucleus)
 Group 8 are the Nobel gasses
 Groups 1& 2 are the metals
 Group 7 are the halogens
o Periods- The rows on the periodic table are called PERIODS
 There are 7 periods on the periodic table
 The period# is equal to the amount of electron shells in an atom
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