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Vocabulary
• Ion – An atom or bonded group of atoms with
a positive or negative charge
• Cation – A positively charged ion
• Anion – A negatively charged ion
• Ionic bond – The electrostatic force that holds
oppositely charged particles together in an
ionic compound
• Ionic compounds – Compounds that contain
ionic bonds
Vocabulary
• Electron affinity – the energy of a neutral,
gaseous atom when an electron is added to
the atom to form a negative ion; the neutral
atom's likelihood of gaining an electron
• Ionization energy – the energy required to
remove an electron from a gaseous atom;
generally increases in moving from left-toright across a period and decreases in moving
down a group.
Atomic Size
Notice the
atomic size
increases as
period
increases and
decreases and
the group
increases.
Ionic Sizes
Ionic Sizes are
different based on
whether electrons
are added or taken
away.
Polyatomic Ions
• An ion made up of two or more atoms bonded
together that acts as a single unit with a net
charge
• Quiz on polyatomic ions on the next slide on
Friday
Common Polyatomic Ions (pg. 221)
Formation of Ionic Compounds
• The charge indicates what ionic compound will
form – oxidation number
• It will always be with one form of cation and one
form of anion.
• Criss-cross
• Subscripts indicate a ratio
• Example: Mg2+ ClMgCl2
Criss-Cross Examples
• Ammonium dichromate
• Sodium chloride
• Calcium oxide
Vocabulary
• Valence electron – The electrons in an atom’s
outermost orbitals; determine the chemical
properties of an element.
• Molecule – Forms when two or more atoms
covalently bond
• Covalent bond – A chemical bond that results
from the sharing of valence electrons
– “co-” means to share
– “-valent” refers to valence electrons
Naming Ionic Compounds
• Cations retain their names
• Anions end in “-ide”
– e.g. oxygen becomes oxide, chlorine becomes chloride
• Metals require a Roman numeral to indicate its
charge.
– e.g. iron (III) oxide. Cation is Fe3+. Anion is O2-. The
compound is Fe2O3
• Polyatomic ions require parentheses if more than
one polyatomic ion is indicated.
– e.g. ammonium sulfide – NH4+ and S2- becomes
(NH4)2S
Practice Naming Ionic Compounds
• NaBr
• Cu(NO3)2
• CaCl2
• Ag2CrO4
• KOH
• NH4ClO4
Naming Covalent Compounds
• Greek prefixes indicate the number of atoms in
each molecule
• If the first element noted is one, “mono” is left
out, e.g. carbon dioxide = CO2
• Mono – one
Hexa – six
• Di – two
Hepta – seven
• Tri – three
Octo – eight
• Tetra – four
Nona – nine
• Penta – five
Deca – ten
Naming Covalent Bonds
• H2O
• CCl4
• SO2
• diarsenic trioxide
• NF3
Lewis Dot Structure
• This is a representation of an element or
molecule showing the valence electrons.
• The element symbol is used, and dots are
placed around it to indicate the valence
electrons.
• Lines are used to show a pair of valence
electrons are shared.
Lewis Dot Structure
• H2 – Hydrogen
• CH4 – Methane
• H2O – Water
• HF – Hydrogen fluoride
• NH3 – Ammonia
You Try
• PH3
• CCl4
• H2S
• SiH4
• HCl
Double and Triple Bonds
• Oxygen shares two pairs • Nitrogen shares three
of electrons, so it has a
pairs of electrons, so it
double bond.
has a triple bond.
• O2
• N2