Chemical Bonding

Question 1

Water formula

Answer 1

H2O

Two hydrogen atoms joined to one oxygen atom

Question 2

Methane formula

Answer 2

CH4

An atom of carbon joined to four atoms of hydrogen

Question 3

Which chemical bonds do you have to describe in examinations

Answer 3

H2
O2
H20
CH4

Question 4

Why are noble gases so unreactive

Answer 4

Elements that have eight electrons in their outer orbit are very unreactive.
The eight electrons in the outer orbit are a stable octet

Question 5

Octet rule

Answer 5

When bonding occurs, atoms try to have eight electrons in the outer orbit

Question 6

Octet rule exceptions

Answer 6

Helium does not have eight electrons in its outer orbit but it’s first and only orbit of electrons is full and is always classifies with the inert gases as its properties are so similar
Hydrogen and lithium tend to teach the electron configuration of helium when chemical bonding occurs

Question 7

Covalent bond

Answer 7

A covalent bond is a bond that consists of shared electrons.
Atoms try to get eight electrons in their outer orbit by sharing electrons with other atoms

Question 8

Hydrogen molecule bond

Answer 8

H2.
The orbits of two hydrogen atoms overlap and share their atom with the other. This gives each atom the stable electron configuration of helium (two electrons in the outer orbit). Each atom has its own electron and a shared electron. The sharing of a pair of electrons is known as a single covalent bond. H - H

Question 9

Methane molecule bond

Answer 9

CH4.
A molecule of methane is one atom of carbon joined to four atoms of hydrogen.
C = 2, 4
H = 1
Carbon needs four more electrons in its outer orbit to get noble gas configuration. It shares each of its four outer electrons with a hydrogen atom.

Question 10

Molecule

Answer 10

A molecule is a group of atoms joined together. It is the smallest particle of an element or compound that can exist independently

Question 11

Water molecule bond

Answer 11

H2O
One atom of oxygen joined to two atoms of hydrogen.
O = 2, 6
H = 1
Oxygen has 6 electrons in its outer orbit so it needs 2 more to get noble gas configuration.
It shares two of its six atoms with two hydrogen atoms

Question 12

Oxygen molecule bond

Answer 12

02
Two oxygen atoms joined together
O = 2, 6
Oxygen has six electrons in its outer orbit and needs two more to get noble gas configuration.

Question 13

Single bond

Answer 13

A single bond is formed when one pair of electrons is shared.

Question 14

Double bond

Answer 14

Represented by ( ) = ( ) double dash
A double bond is formed when two pairs of electrons are shared.

Question 15

Ionic bond

Answer 15

An ionic bond is the force of attraction between positive and negative ions in a compound

Question 16

Ions

Answer 16

An ion is a charged ion or group of ions.
Table salt consists of particles called ions and are represented as Na+ and Cl-
Na+ = sodium ion. Lost an electron which are negatively charged so it is positively charged
Cl- = chloride atom. Gained an electron which are positively charged so it is negatively charged.

Question 17

Sodium chloride ionic bond

Answer 17

NaCl
Na = 2, 8, 1 (loses one electron) Na+ = 2, 8
Cl = 2, 8, 7 (gains an electron) Cl- = 2, 8, 8
Sodium loses its one atom in the outer orbit so it has a full outer shell and gives it to chlorine so it has a full outer shell.

Question 18

Magnesium oxide ionic bond

Answer 18

MgO
Mg = 2, 8, 2 (loses two electrons) Mg2+ = 2, 8
O = 2, 6 (gains two electrons) O2- = 2, 8
Magnesium gives its two atoms in its outer orbit to oxygen so oxygen has a full outer shell.
Magnesium ion
Oxide ion

Question 19

Properties of ionic compounds

Answer 19

• Ionic compounds are usually solid at room temperature because of the attraction between the oppositely charged ions. In sodium chloride, the attraction is so strong that it forms a definite shape and crystals.
• They have a high melting and boiling point because it takes a lot of energy to separate the strongly attracted ions, NaCl melting point = 800c. NaCl boiling point = 1500c.
• They dissolve in water because water is attracted to ions and they are pulled away into solution
• They conduct electricity when melted or dissolved because the ions are free to move.

Question 20

Properties of covalent compounds

Answer 20

• Usually a liquid or gas at room temperature because the atoms in the molecules are held together by covalent bonds but no strong forces of attraction between the molecules, e.g. water and methane.
• Low melting and boiling points as not much energy is needed to separate the molecules as there are no strong forces of attraction between the molecules.
• Many don’t dissolve in water because they don’t contain ions which water is attracted to.
• They do not conduct electricity because they do not contain ions

Question 21

To investigate the ability of ionic me covalent substances to conduct electricity

Answer 21

Apparatus : power supply, bulb, leads, crocodile clips, carbon electrodes, wash bottles
Chemicals : water, copper sulfate solution, methylated spirits, sodium chloride solution, table sugar solution, paraffin oil
Method :
1. Set up the apparatus as shown in the diagram
2. Insert the carbon electrodes in the copper sulfate solution.
3. Write down what you observe.
4. Repeat with other solutions, washing the carbon electrodes with the wash bottles between solutions
Conclusion : solutions that contain ions conduct an electric current