End Of Unit Questions

Question 1

Which electrons in an atom are involved in bonding?

Answer 1

Electrons in the highest occupied energy level

Question 2

What happens to the electrons in atoms when ionic bonds are formed?

Answer 2

They are transferred or metal atoms lose electrons and non metal atoms gain electrons

Question 3

What happens to the electrons in atoms when covalent bonds are formed?

Answer 3

They are shared, for each pair of covalent bonds one pair of electrons is shared

Question 4

Why do the elements in group 1 form ions with a single positive charge?

Answer 4

They lose their one outer electron

Question 5

Why do the elements in group 7 form ions with a single negative charge?

Answer 5

They gain one electron to their outer shell

Question 6

Which of the following substances are made of molecules?

KCl, H2O, C2H6, MgO, CO2, NaNO3

Answer 6

H2O, C2H6, CO2

Question 7

Why can the structure of a metallic element like copper be represented by lots of small spheres the same size packed together?

Answer 7

The atoms in copper are all the same size and are spherical

Question 8

Write the correct formula for each of the following: lithium chloride, sodium oxide, calcium fluoride, magnesium hydroxide, sodium sulfate, calcium nitrate.

Answer 8

• LiCl
• Na2O
• CaF2
• Mg(OH)2
• NaSO4
• Ca(NO3)2

Question 9

Why do ionic compounds have giant structures?

Answer 9

The attractive forces between oppositely charged ions act in all directions, so the ions pack closely together in a regular arrangement (lattice) ions are very small so crystal contains many ions

Question 10

Draw diagrams using symbols and lines to show the covalent bonds in F2, O2, HBr, H2O, NH3

Answer 10

•F-F
•O=O
•H-Br
•H-O-H
•H
  |
 N-H 
  |
 H

Question 11

Explain why silicon has a giant structure

Answer 11

Silicon atoms in group 4 form 4 covalent bonds, each silicon atom can join to 4 others, the bonds are strong, this continues so that a giant structure is formed

Question 12

Explain how the atoms in a piece of sodium metal are held together

Answer 12

The outer electrons delocalise leaving a lattice of positive ions, the delocalised electrons attract the positive ions, the electrostatic forces are strong and these hold the ions in position

Question 13

What is a compound?

Answer 13

A substance made of two or more elements that have reacted together or that are chemically bonded together