Name: ___________________________________
Unit 3 Review packet
1. When and how an ionic bond is formed?
An ionic bond is formed when a metal transfers its electrons to a nonmetal. The metal and
nonmetal ions (cation and anion) are held together by opposite charges (electrostatic forces)
in a crystal lattice.
2. What should be the electronegativity difference to form an ionic bond?
The difference should be equal to or more than 1.67.
3. When and how a covalent bond is formed?
A covalent bond is formed between two nonmetal atoms when they share electrons. They
share electrons so that each atom (except H and B) has access to 8 electrons. This is called
the octet rule.
Hydrogen is happy with 2 electrons
Boron is happy with 6 electrons
4. Show transfer of electrons when magnesium reacts with oxygen forming an ionic bond.
Mg transfers two electrons to O, so both atoms are stable.
5. Write 3 differences between physical properties of ionic and covalent compounds.
Ionic- have high melting and boiling points. Covalent- low melting and boiling points.
Ionic- dissolve easily in water. Covalent- sometimes dissolve.
Ionic- conduct electricity when dissolved in water. Covalent- do not conduct electricity in
water.
6. Why are ionic compounds very good electrolytes?
_They dissolve into ions in water (100 % dissociation) , allowing them to conduct electricity.
7. Fill the following table with correct information.
Family Valence electrons Charge Cation /Anion
Alkali metals 1 +1 Cation
Alkaline earth metals 2 +2 Cation
Boron family 3 +3 Cation
Nitrogen family 5 -3 Anion
Oxygen family 6 -2 Anion
Halogens 7 -1 Anion
Noble gases 8 0 No ions formed
8. Write the formulas for the following compounds when the names are given to you.
Remember to first figure out if the compound is ionic or covalent.
Name Formula Name Formula
KBr Germanium tetrachloride GeCl4
Potassium bromide
CaI2 Ag2SO4
Calcium iodide Silver sulfate
Al2(CO3)3 Cu(NO3)2
Aluminum carbonate Copper (II) nitrate
NH4OH Silicon trioxide SiO3
Ammonium hydroxide
Pb(NO3)4 Ba3N2
Lead (IV) nitrate Barium nitride
Co2S3 Sulfur trioxide SO3
Cobalt (III) sulfide
Nitrogen trifluoride NF3 V2(SO4)5
Vanadium (V) sulfate
Dicarbon tetrahydride C2H4 C4H6
Tetracarbon hexahydride
9. Write the names for the following compounds when the formulas are given to you.
Remember to first figure out if the compound is ionic or covalent.
Formula Name Formula Name
Pb2S Lead (I) sulfide SeF6 Selenium hexafluoride
C2O2 Dicarbon dioxide TiO2 Titanium (IV) oxide
Mg(NO3)2 ZnBr2 Zinc bromide
Magnesium nitrate
N2F6 Fe(OH)3 Iron (III) hydroxide
Dinitrogen hexafluoride
Formula Name Formula Name
NH4I Cr3(PO4)2 Chromium (II)
Ammonium iodide phosphate
Au3N Gold (I) nitride XeI4 Xenon tetraiodide
(NH4)2CO3 Ammonium carbonate Rb2O Rubidium oxide
CH4 Carbon tetrahydride Be3N2 Beryllium nitride
10. Draw the Lewis dot diagrams for the following covalent compounds and predict their
shapes and bond angles
Name Lewis dot diagram Shape Bond angle
(IB ONLY)
Nitrogen Linear Not applicable
Molecule (only 2 atoms)
Carbon Tetrahedral 109.5 o
tetraiodide
Phosphorus Trigonal pyramidal 107 o
trihydride
Sulfur Trigonal planar 120 o
trioxide
11. Draw the Lewis dot diagrams for the following covalent compounds and predict their
shapes and bond angles
Name Lewis dot diagram Shape Bond angle
(IB ONLY)
Boron Trigonal planar 120o
trihydride
Dihydrogen Bent 104.5o
monosulfide
Carbon Linear 180o
disulfide
Oxygen Linear Not applicable
molecule (only 2 atoms)
12. Although tetrahedral, trigonal pyramidal, and bent have similar bond angles, they are not
the same. What are their bond angles and why are they different? Why are they similar?
(IB ONLY)
The bond angles are 109.5, 107.5, and 104.5 (respectively). They are similar because
they all have 4 electron domains. They are different because they have increasing
numbers of non-bonded domains/lone pairs (0, 1, and 2) around the central atom.
The lone pairs repel the electrons in the bonds more than bonded pairs do. Thus, as
lone pairs increase, the repulsion increases, and the bond angles get smaller.
13. How many different elements are there in the following compounds?
a) NH4OH _3_ (N, H, O) c) CO _2_(C, O)
b) (NH4)3PO4 ___4___ (N, H, P, O) d) CH3COOH__3__(C, H, O)
14. How many atoms of each element are present in the following formulas?
a. PO
2 5 P=2 O=5
b. CaCO 3 Ca = 1 C= 1 O=3
c. NH (SO )
4 4 2 N=1 H=4 S=2 O= 8
