4.1.1.1 Atoms, elements and compounds

Question 1

What are all substances made of?

Answer 1

• All substances are made of atoms.
• An atom is the smallest part of an element that can exist.

Question 2

How are atoms of each element represented?
- give examples

Answer 2

• Atoms of each element are represented by a chemical symbol, eg O represents an atom of oxygen, Na represents an atom of sodium.

Question 3

How many different elements are there and how are they shown?

Answer 3

• There are about 100 different elements
• Elements are shown in the periodic table

Question 4

How are compounds formed?

Answer 4

• Compounds are formed from elements by chemical reactions.

Question 5

What do chemical reactions involve?

Answer 5

• Chemical reactions always involve the formation of one or more new substances, and often involve a detectable energy change.

Question 6

What do compounds contain?

Answer 6

• Compounds contain two or more elements chemically combined in fixed proportions and can be represented by formulae using the symbols of the atoms from which they were formed

Question 7

How can compounds be separated?

Answer 7

• Compounds can only be separated into elements by chemical reactions.

Question 8

How can chemical reactions be represented?

Answer 8

• Chemical reactions can be represented by word equations or equations using symbols and formulae

Question 9

Can you use the names and symbols in the periodic table: for?

Answer 9

• The first 20 elements in the periodic table, the elements in Groups 1 and 7, and other elements in this specification

Question 10

Can you name compounds of elements given?

Answer 10

• Of elements from the given formulae or symbol equations

Question 11

Can you write word equations for the reactions in the specification?
- magnesium and oxygen react, write the word equation.

Answer 11

• Magnesium+ Oxygen = Magnesium Oxide

Question 12

Can you write formulae and balanced chemical equations for the reactions in the specification?
- write the balanced symbol equation for magnesium and oxygen

Answer 12

2Mg + O2 = 2MgO

Question 13

Can you write balanced half equations and ionic equations where appropriate?
- what is it?

Answer 13

• A half equation shows how electronics are transferred when a substance is reduced or oxidised, e.g. at an electrode during electrolysis