Transcript 4.1 Notes - power point

4.1 Atomic Theory & Bonding
ATOM: smallest particle of an element, has a neutral
charge.
PEN = proton(s) + electron(s) + neutron(s)
ELEMENT: made up of 1 type of atom (eg.oxygen O)
IONS: atoms with charges (eg. oxygen is O2-)
MOLECULES: groups of covalently bonded atoms
(eg. oxygen molecules are O2)
COMPOUNDS: are made up of at least 2 atoms
bonded together.
 Hydrogen and oxygen are atoms/elements
 H2O is a compound
Structure of an Atom:
Name
Charg
Symbol
e
Location
Atomic
Mass
Proton
p
1+
nucleus
1 AMU
Neutron
n
0
nucleus
1 AMU
Electron
e
1–
area surrounding
the nucleus
1/1836 (0)
Numbers to Remember :
Protons = Atomic Number
Neutrons = Mass number – Atomic number (Mass
# - proton #).
Neutrons + Protons = Mass #
Electrons in an atom = atomic number (also
proton #)
Electrons in an ion = atomic number – ion charge
Families of the Periodic Table:
 Columns of elements are called groups, or families
 All elements in a family have…
 similar properties
 bond with other elements in similar ways
 have the same number of valence electrons
 Family names (on the periodic table!):
 Group 1 = alkali metals (1+, highly reactive)
 Group 2 = alkaline earth metals (2+, reactive)
 Group 17 = the halogens (1-, very reactive)
 Group 18 = noble gases (0, unreactive)
 Periods are horizontal rows on the periodic table.
INCREASING REACTIVITY
Where are the
following?
• Atomic
Number
• Period
• Group/Family
• Metals
• Non-metals
• Transition
metals
• Metalloids
• Alkali metals
• Alkaline earth
metals
• Halogens
• Noble gases
Periodic Table & Ion Formation:
 Ions: Atoms that gain and lose electrons to become
stable (full valence shells).
 1. Cations: metals that lose electrons & form
positive ions (Na+)
 Multivalent: Some metals can have more than
one charge (Fe2+ or Fe3+).
 2. Anions: Non-metals gain electrons & form
negative ions (O-2)
Bohr Diagrams:
 Bohr diagrams show how many electrons
appear in each electron shell around an
atom. (2, 8, 8, 18, 18)
 Valence electrons: electrons in the outermost
shell ONLY.
 If the valence shell is full = stable
 If the valence shell is not full = reactive
Bohr Diagrams
What element is this?
•It has 2 + 8 + 8 = 18
electrons, and therefore
18 protons
18 p
22 n
•It has 8 electrons in the
outer (valence) shell
Argon!
Ionic Bonds:
 Formed between Metals (cations) & non-metals (anions).
 Valence electrons are transferred from metal to nonmetal.
 Eg. Li2O
+
Lithium
Oxygen
Electrons are transferred from
the cations to the anion
Covalent Bonds:
Li+
O2Li+
Lithium oxide,
Li2O
 Formed between two or more non-metals
 Valence electrons are shared between atoms
 Eg. HF
+
Hydrogen
Hydrogen fluoride
Fluorine
Electrons are shared
Lewis Diagrams:
 Only valence electrons are shown
 Dots representing valence electrons are placed
around the element symbols (on 4 sides,
imagine a box around the symbol)
 Electron dots are placed singularly,
then they are paired.
Ex: Nitrogen
atom
Lewis Diagrams for Ions:
Ex. Nitrogen ion
 Remove or add electron dots to
make full valence shells.
 Square brackets and the charge
are placed around each ion
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Be
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Cl
Each beryllium has two
electrons to transfer
away, and each chlorine
wants one more electron
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Cl
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Be
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Cl
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Cl
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Since Be2+ wants to
donate 2 electrons and
each Cl– wants to
accept only one, two Cl–
ions are necessary
–
2+
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Be
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Cl
The ionic compound
Beryllium chloride is
formed
–
Lewis Diagrams For Covalent Bonds:
 valence electrons are drawn to show sharing of
electrons.
 Remember: All atoms “like” to have a full valence
shell
 The shared pairs (“bonding pairs”) of electrons
are usually drawn as a straight line
 “lone pairs” are the electrons not shared