the atom i- theories about the atom: a- t he term a aa atom comes from the greek w ord meaning “...
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II- II- HowHow AtomsAtoms DifferDiffer
A-A- All atoms of an elementelement have the same numbernumber of protonsprotons. The number of
protons determinesdetermines what the elementelement is.
1- 1- AtomicAtomic NumberNumber is the numbernumber of protonsprotons of an
atom.
2- 2- MassMass NumberNumber:: is the total numbernumber of ProtonsProtons and NeutronsNeutrons in an atomatom.
a-a- To find the numbernumber of neutronsneutrons in an atomatom all you do is
subtractsubtract the atomicatomic numbernumber from the massmass numbernumber.
Mass Number
B-B-IsotopesIsotopes:: Atoms of the samesame element with the samesame
atomic number but a differentdifferent number of neutronsneutrons.
III-III-ClassifyingClassifying ElementsElements::
A-A-TheThe PeriodicPeriodic TableTable:: Was created by MendeleevMendeleev, he put the elementselements with the same characteristicscharacteristics into columnscolumns.
1-1-The elements lineline up in increasingincreasing atomicatomic numbers.
B- B- ArrangementArrangement ofof TableTable::
1-1-Each rowrow is called a periodperiod and each columncolumn is called a groupgroup.
2-2-If you know somethingsomething about an elementelement in a
groupgroup you know somethingsomething about
them allall.
3-3-Each box has an element’s symbolsymbol, name, atomicatomic numbernumber, massmass number, and the number of electronselectrons in each energy energy levellevel.
13
26.98
AlAluminum
2
8
3
Atomic Number
Number of electrons in each energy level
Average atomic mass
Symbol
Name