# Understand Atomic Structure and Properties of Elements

In this worksheet, students will learn how the structure of the atom determines both its position in the Periodic Table and its properties.

### QUESTION 1 of 10

An atom is the smallest chemical entity. Its name comes from a Greek word that means 'a whole', 'a unit', 'something that cannot be broken'. Of course, scientists have now actually managed to separate atoms into their components, but they are still the smallest units that make up chemical elements.

An atom is made up of a nucleus and electrons that surround it. The nucleus carries a positive charge and the electrons a negative charge. The nucleus is made up of protons, that carry the positive charge, and neutrons, which carry no charge because they are neutral. You can see how atoms are represented in diagram form below. In reality, they are a bit more complicated! You can draw the electrons as dots or crosses.

Each atom has an atomic number and this is written next to the symbol of the corresponding element in the periodic table. Yes, you guessed right: each element has its own atom, that's what makes each element different.

The atomic number is the number of protons in the nucleus. Usually, the number of protons is the same as the number of neutrons - but not always!. The number of protons is the same as the number of electrons.

Atoms also have a mass number. This is the total number of protons and neutrons. The particles of an atom also have a mass, but because it is tiny we call it relative mass, so protons and neutrons have a relative mass of 1 (no unit!), whereas electrons are so tiny that their mass does not even count.

Some atoms of the same element have the same atomic number, but a different mass number (due to the different number of neutrons). These are called isotopes.

Electrons are arranged around the nucleus in shells (different energy levels) shown in the diagram above. Suppose the atom shown is lithium - we would write it as Li 2,1. This means the lithium atom has 2 electrons on the first shell (inner shell, near the nucleus) and one on the outer shell. The first shell can have a maximum of 2 electrons, the second 8, the third 8 and the fourth 2.

The properties of the different elements depend on the number of protons and electrons they have. They are placed on the periodic table in groups in the order of their atomic number.

Let's move on to the questions now.

What particles can you find in an atom?

Electronians

Protoniums

Protons

Neutrons

What is an atom's atomic number?

The number of protons

The number of neutrons

The number of protons and neutrons

Is the following statement true or false?

The mass number is the number of protons and electrons.

True

False

What is the relative mass of each of the particles within an atom?

 Mass of 1 Mass of 0 Protons Neutrons Electrons

What is the overall charge of an atom?

Neutral

Positive

Negative

Is the following statement true or false?

Elements are placed in the periodic table in bands.

True

False

In what form do electrons surround the nucleus?

Boxes

Shells

Atoms

What are isotopes?

Elements with the same mass number and a different atomic number

Elements with the same number of protons but a different number of neutrons

Elements with a different number of electrons

Look at the diagram showing the atoms of hydrogen and helium.

How would you write the structure of hydrogen?

H 1 e

H 1

H 1, 2

Look at the diagram of the atomic structure of sodium (Na).

How would you write it?

Na 2, 7, 1

Na 2, 8, 1

Na 1, 8, 2

• Question 1

What particles can you find in an atom?

Protons
Neutrons
EDDIE SAYS
Did you get caught out by some of these ridiculous names?! The first two options sound more like alien creatures from some distant galaxy, don't they? The correct answer was options three and four. An atom contains protons and neutrons, as well as electrons, which were not included in the choices here.
• Question 2

What is an atom's atomic number?

The number of protons
EDDIE SAYS
It can be easy to get muddled with all these numbers but it is important to get it sorted and, once you have learned which is which, there are some easy marks to be gained on the exam paper! The atomic number is the number of protons in an atom.
• Question 3

Is the following statement true or false?

The mass number is the number of protons and electrons.

False
EDDIE SAYS
Here's another number one to get your head around. Make sure you know the difference between atomic and mass numbers and you'll be laughing in the exam! The mass number is the number of protons and neutrons added together.
• Question 4

What is the relative mass of each of the particles within an atom?

 Mass of 1 Mass of 0 Protons Neutrons Electrons
EDDIE SAYS
Not many numbers to remember here, but did you choose the right ones? Both protons and neutrons have a relative mass of only 1. An electron's mass is so small that it doesn't even count, so it is zero!
• Question 5

What is the overall charge of an atom?

Neutral
EDDIE SAYS
You need to know the charges on the different particles to be able to work this one out. Protons are positive, electrons are negative and neutrons are neutral. The number of protons and electrons is the same (which would cancel out each other's charge) so the overall charge will be neutral.
• Question 6

Is the following statement true or false?

Elements are placed in the periodic table in bands.

False
EDDIE SAYS
Elements are placed in the periodic table in groups according to the atomic number and the number of electrons on the outer shell.
• Question 7

In what form do electrons surround the nucleus?

Shells
EDDIE SAYS
Electrons surround the nucleus in a series of shells. The inner shell contains a maximum of 2 electrons and the next two shells contain a maximum of 8.
• Question 8

What are isotopes?

Elements with the same number of protons but a different number of neutrons
EDDIE SAYS
This was a bit of a confusing question, so don't worry if you found it tricky. Isotopes are elements with the same atomic number (number of protons) and a different mass number (total number of protons and neutrons). This means that only the number of neutrons is different, as the number of protons of the same element is always the same.
• Question 9

Look at the diagram showing the atoms of hydrogen and helium.

How would you write the structure of hydrogen?

H 1
EDDIE SAYS
There is so much stuff you need to remember in this topic, but it is important to make sure you understand this because you are bound to have questions on it in the exam. Hydrogen has only one electron and that is on the first shell. H is the symbol for hydrogen, so you would write this as H 1.
• Question 10

Look at the diagram of the atomic structure of sodium (Na).

How would you write it?

Na 2, 8, 1
EDDIE SAYS
This looks tricky but actually all you need to do is look at the diagram and do some counting! Sodium has 2 electrons on the first shell, 8 on the second and 1 on the third, so it is written Na 2, 8, 1. Well done for completing this rather challenging activity. The more you practise this sort of question, the easier these number problems will become.
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