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Ionic, Metallic and Covalent Bonding
Writing and Naming Formulas
Chemical bond
force that holds two atoms together
opposites attract
the attraction between the positive nucleus of one atom and the negative electrons of another atom
Chemical bonds are formed by:
or by the attraction between positive and negative ions
Krypton
Iron in oxygen Potassium in water
Valence electrons
found in outermost energy level
electrons available to be lost, gained, or shared in the formation of chemical compounds
Octet Rule
Atoms tend to gain, lose, or share electrons in order to acquire a full set of eight valence electrons; stable noble gas configuration.
Three types of bonds:1. Ionic transfer of electrons between metal and nonmetal (or polyatomic ion)2. Metallic electron sea model; atoms of same metal 3. Covalent – sharing of electrons between nonmetals; may be same or different elements
atom, or a bonded group of atoms, that has a positive or negative charge
Ion
Ionic bond
electrostatic force that holds oppositely charged particles together
Positive ion formation
atom loses one or more valence electrons
cations
Write an electron configuration for sodium.
Write an electron configuration for neon.
What is the only difference in the electron configurations of these two elements?
Metals tend to lose electrons to form positive ions called cations.
Metals lose all valence electrons so that next energy level is full.
MagnesiumAluminumLithiumBariumPotassiumGallium
Write an electron dot notation for each metal:
Predict if each would lose or gain electrons when forming compounds:
MagnesiumAluminumLithiumBariumPotassiumGallium
How many electrons would each lose?
MagnesiumAluminumLithiumBariumPotassiumGallium
What cations would the following elements form? Write symbol and charge.
MagnesiumAluminumLithiumBariumPotassiumGallium
Use group number to predict charge of metal ion for representative elements only.
Group 1 1+
Group 2 2+
Group 13 3+
Transition metals
d block; filling inner energy levels
sometimes inner electrons take part in bonding
most form more than one common ion
Transition metals that form only one common ion:
silver Ag+
zinc Zn2+
Negative ion formation
atom gains one or more valence electrons
anion
Write an electron configuration for chlorine.
Write an electron configuration for argon.
What is the only difference in the electron configurations of these two elements?
Nonmetals tend to gain electrons to form negative ions called anions.
Nonmetals gain enough electrons to obtain full octet (8).
Write an electron dot notation for each nonmetal:
SulfurNitrogenIodinePhosphorusFluorineOxygen
Predict if each would lose or gain electrons when forming compounds:
SulfurNitrogenIodinePhosphorusFluorineOxygen
How many electrons would each gain?
SulfurNitrogenIodinePhosphorusFluorineOxygen
What anions would the following elements form?Write symbol and charge.
SulfurNitrogenIodinePhosphorusFluorineOxygen
Use group number to predict charge on nonmetals.
Group 18 0
Group 17 1-
Group 16 2-
Group 15 3-
Writing formulas for binary ionic compounds:
1. Write symbol and charge for cation and anion.
2. Use subscripts to show the ratio of ions.
Ex: lithium and oxygen
Cation always written first.
Ionic formulas, subscripts show simplest ratio.
Write formulas for the binary ionic compoundsformed between thefollowing elements:
a. potassium and iodine
b. magnesium and chlorine
c. sodium and sulfur
d. aluminum and nitrogen
e. aluminum and sulfur
Naming binary ionic compounds:
cation (metal) name of element; always written first
anion (nonmetal) name of element with an ‘ide’ ending
Name the binary ionic compounds indicated by the following formulas:
a. AgClb. ZnOc. CaBr2
d. SrF2
e. BaOf. CaCl2
Some metals form more than one common ion; most of the transition metals and tin and lead.
Transition metals – d electrons can take part in bonding
How form multiple ions?
Write noble gas notation for tin:
[Kr] 5s24d105p2
Sn2+ or Sn4+
Fe2+ Cl-
iron(II) chloride
Fe3+ Cl-
iron(III) chloride
The charge on the metal is written as a Roman numeral in the name of compound.
FeCl2
FeCl3
Transition metals that form only one common ion:
silver Ag+
zinc Zn2+
Metals that form only one common ion do not need Roman numeral.
NaBr sodium bromide
Write the formula and name for the compounds formedbetween the following ions(use Roman numerals):
a. Cu2+ and Br -
b. Fe2+ and O2-
c. Pb2+ and Cl-
d. Hg2+ and S2-
e. Sn2+ and F-
f. Fe3+ and O2-
Writing names with Romannumerals:
1. Determine total negative charge.
2. Total negative charge equals total positive charge.
3. Charge on one positive ion is Roman numeral.
Ionic compounds containingpolyatomic ions:
Write formulas as you would for binary ionic compounds;use parentheses if adding subscript to polyatomic ion.
Write formulas for the following compounds:
magnesium carbonate
magnesium hydroxide
Write formulas for the following ionic compounds:
a. lithium nitrateb. copper(II) sulfatec. sodium carbonated. calcium nitritee. potassium perchlorate
When naming compounds,do not change name ofpolyatomic ion.
Three types of bonds:1. Ionic transfer of electrons between metal and nonmetal (or polyatomic ion)2. Metallic electron sea model; atoms of same metal 3. Covalent – sharing of electrons between nonmetals; may be same or different elements
Why do atoms bond?
to obtain a full outer energy level; complete octet
to become more stable; lower potential energy
Electronegativity (EN)
indicates relative ability of an atom to attract electrons in a chemical bond
Metals
low EN; tend to give up electrons
Nonmetals
high EN; tend to gain electrons
What happens when two nonmetals, with similar EN, react?
Covalent bond
chemical bond that results from the sharing of valence electrons
generally formed between two nonmetals (same or different element)
electrons are attracted by the nuclei of two different atoms
Molecule
formed when two or more atoms bond covalently
Naming binary molecular compounds
1. First element; use entire element name.
2. Second element ends in –ide.
3. Prefixes are used to indicate the number of atoms of each element – the subscripts.
N2O4 dinitrogen tetroxide
If first element has one atom, mono omitted.
CO carbon monoxide
Name the followingmolecular compounds:
a. PF3
b. XeF4
c. As2O5
d. CCl4
Write formulas for thefollowing compounds:
a. carbon dioxideb. dinitrogen pentoxidec. silicon tetrafluoride
Ionic compounds
composed of large numbers of cations and anions; crystal lattice
formula unit – smallest whole number ratio of ions
Molecular compounds
composed of discrete (individual) molecules of covalently bonded atoms
molecular formulas do not need to be lowest ratio of atoms
C2H4
a substance that produces hydrogen ions (H+) when dissolved in water
Acid
molecular compound that reacts with water to form ions
1. binary acid – two elements; hydrogen and a nonmetal
name begins with prefix‘hydro’ and ends with ‘ic’
HCl hydrochloric acid
2. oxyacid – hydrogen, oxygen, and a nonmetal; many formed from polyatomic ions
if name of polyatomic ion ends with ‘ate’ , name of acid ends with ‘ic’
H2SO4 sulfuric acid
Binary acid
hydro _____ ic acid
Oxyacid
______ ic acid
Name the following acids:
H2CO3
HBr
Writing formulas for acids:
start with H+
determine charge on nonmetal ion or polyatomic ion
add subscripts if needed to make neutral compound
Write formulas for the following acids:
hydrofluoric acid
phosphoric acid
Electronegativity (EN)
indicates the relative ability of an atom to attract electrons in a chemical bond
Type of bond formed between two atoms depends on the difference in electronegativities (EN) of the atoms.
Difference in electronegativity (EN)
locate elements on periodic table
subtract values for EN
EN always positive
Ex: hydrogen and chlorine
EN = 3.16 – 2.20 = 0.96
Polar covalent bond
unequal sharing of electrons
one atom pulling electrons towards itself
Covalent bonds may be:
atom with higher EN value has a partial negative charge ()
atom with lower EN value has a partial positive charge ()
Ex: hydrogen and chlorine
EN = 3.16 – 2.20 = 0.96
Nonpolar covalent bond
electrons shared equally
no partial charges
Covalent bonds may be:
Most bonds are not completely ionic or covalent.
EN Bond Character
> 1.7 Ionic
0.4 – 1.7 polar covalent
< 0.4nonpolar covalent
Classify the following bonds as nonpolar- covalent, polar-covalent, or ionic. If bond is polar-covalent, assign partial charges.
C and H
H and Br
Cs and S
Properties of Compounds
depend on the strength of the attractive forces between particles
ions arranged in a regular repeating pattern called crystal lattice
Properties of ionic compounds
ions held together by strongionic bonds
Properties of ionic compounds
high melting and boiling points; much energy needed to separate ions
hard, rigid, brittle solids
Properties of ionic compounds
do not conduct electricity in solid state
aqueous solutions and liquid states are electrolytes - conduct electricity since ions are free to move
Properties of molecularcompounds
covalent bonds between atoms are strong, but attraction forces between molecules are weak
relatively weak forces of attraction between molecules
Intermolecular forces
also known as van der Waals forces
Properties of molecular compounds
relatively low melting and boiling points; many gases or liquids at room temperature
Properties of molecular compounds
do not conduct electricity when dissolved in water; except for acids
Metallic bond
outer energy levels of metal atoms overlap
valence electrons are shared by several atoms; delocalized (free to move)
electron sea model
attraction of a metallic cation for delocalized electrons
Metallic bond
Properties of metals
Properties of metals
moderately high melting points and high boiling points; most solids are room temperature
the more delocalized electrons a metal has, the greater its strength and hardness; groups 1 & 2 soft
Metals are malleable (hammered into thin sheets) and ductile (drawn into wires.)
good conductors of heat and electricity; electrons mobile
delocalized electrons interact with light, giving metals luster (shiny)
Three types of bonds:
1.Ionic – transfer of e-
metal and nonmetal
2. Metallic electron sea model; atoms of same metal
3. Covalent – sharing of e-
nonmetals
+ -
+
• Nonpolar Covalent - no charges
• Polar Covalent - partial charges
