Writing and balancing chemical equations

Question 1

How do you find the charge of elements in an ionic compound?

Answer 1

Most ionic compounds contain a metal and non-metal. Metals lose outer shell electron and become positively charged. Non-metals gains electrons and become negatively charged. E.g Li has 1 outer electron so loses it and become positively charged by one. Nitrogen has 5 outer electrons so gains 3 and becomes negatively charged by 3.

Question 2

How do you write the formula of an ionic compound?

Answer 2

Use the cross method. If the compound is aluminium oxide, the charge is Al3+ and the charge of oxide is O2- so cross the numbers and the formula becomes Al2O3.

Question 3

What are the properties of the alkali metals?

Answer 3

• They are soft and can be cut by a knife
• They have a low density, lithium, sodium and potassium float on water
• They have lower melting and boiling points than other metals, which decrease going down the ground, as the atoms become larger, attraction to the nucleus becomes weaker and reactivity increases
• They all have 1 outer electron

Question 4

What are the alkali metals?

Answer 4

Lithium - Li
Sodium - Na
Potassium - K
Rubidium - Rb
Caesium - Cs
Francium - Fr

Question 5

How do alkali metals react with oxygen?

Answer 5

All alkali metals react with oxygen in the air to form metal oxides.
The speed with which alkali metals react with oxygen increase going own the group.

Question 6

How are alkali metals stored?

Answer 6

In oil to prevent them from reacting with oxygen and tarnishing.

Question 7

Why are they called alkali metals?

Answer 7

Alkali metals react with water to produce heat, hydrogen gas, and the corresponding metal hydroxide. The heat produced by this reaction may ignite the hydrogen or the metal itself, resulting in a fire or an explosion.

Question 8

What is an isotope?

Answer 8

Atoms with different numbers of neutrons are called isotopes.

Question 9

What are the properties of isotopes?

Answer 9

Isotopes mainly have similar or the same chemical properties as chemical properties are based on electrons but mass will be different and may or may not be radioactive.

Question 10

What are the properties of the Halogens?

Answer 10

• They have low melting points and boiling points. Their melting points and boiling points increase going down the group
• They are poor conductors of heat and electricity

Question 11

What are the Halogens?

Answer 11

Fluorine - F
Chlorine - Cl
Bromine - Br
Iodine - I
Astatine - At

Question 12

In Group 7 (the Halogens) what is the unique trend going down the group?

Answer 12

The reactivity decreases going down.

Question 13

What do the halogens form in their ionic compounds with metals?

Answer 13

They all form ions with a single negative charge.

Question 14

What do the halogens form with other non-metals?

Answer 14

They form covalent compounds by sharing electrons with other non-metals.

Question 15

What happens in a reaction with a more reactive and less reactive halogen in a solution of one of its salts?

Answer 15

The more reactive halogen DISPLACES the less reactive halogen.

Question 16

What is electrostatic force?

Answer 16

Electrostatic attraction is what you get between oppositely charged ions in a giant ionic lattice, e.g. NaCl, where the Na+ and Cl- ions are attracted to one another. Electrostatic attraction is not an intermolecular force, as it is not between molecules.

Question 17

What is intermolecular force?

Answer 17

Intermolecular forces occur between simple covalent molecules, e.g. H2O, and CH4. Intermolecular forces are very weak in comparison to a covalent / ionic bond, and therefore can be broken easily. That is why the melting / boiling temperatures of simple covalent molecules is low.

Question 18

Why do the halogens decrease in reactivity going down the group?

Answer 18

Non-metal atoms gain electrons when they react with metals. … The electrons in the outer shell move further away from the nucleus as we go down the group and the attraction force between the electrons and the nucleus become weaker and weaker.

Question 19

What are the properties of the transition metals?

Answer 19

• They are good conductors of electricity and thermal energy
• They are hard and strong
• They have high densities
• They have high melting points (except mercury, liquid at room temp
• They are harder, stronger and denser than the alkali metals but less reactive

Question 20

What do transition metals form in compounds that are often coloured?

Answer 20

A transition element can form ions with different charges e.g iron can be Fe2+ or Fe3+