C3a What are Atoms Like?

What is an atom?

What is the structure of an atom?

Atoms are made up from a central ___________ that is orbited by __________

The nucleus is made up of ________________ and ____________________.

So, atoms are made up from 3 sub-atomic particles; ______________,

_______________ and _____________________.

What are protons, neutrons and electrons?

sub-atomic particle charge mass

protons

neutrons

electrons

IMPORTANT FACT

An atom always has an ____________ number of ________________ (+) and

________________ (-). This means that they have no overall charge – we

say that they are ______________________.

How can we work out the number of protons, neutrons and electrons in an

atom?

Each different type of atom is a different ______________ and has a

different number of ____________, ____________ and ______________.

23

sodium

Everything on Earth is made up from about _________ different elements

and they are listed on the periodic table:

Consider Sodium

Each element can be found in its own square. Find sodium and copy the

information into this box:

Na

Tasks

1. Using a periodic table, find the symbol and the atomic number for:

a) Helium

b) Potassium

What can we tell from this information?

c) Iron

d) Copper

e) Bromine

2. Complete the following table:

Name Symbol Atomic Number Mass Number

Lithium Li 3 7

Carbon

Calcium

Aluminium

Iron

3. Now calculate the number of protons, neutrons and electrons in one

atom of each element from the table above.

Remember: Atomic number = number of protons (there must be an equal number of

electrons)

Mass number = number of protons + neutrons

Name Number of

protons

Number of

neutrons

Number of

Electrons

Lithium 3 7-3 = 4 3

Carbon

Calcium

Aluminium

Iron

How are elements arranged in the Periodic Table?

Find the following elements, in order, Hydrogen

Helium

Lithium

Beryllium

Boron

Carbon

Nitrogen

Oxygen

Fluorine

Neon

Sodium

What do you notice about the atomic numbers and atomic masses of these

elements? Give as much detail about any trends (patterns) that you spot.

Answer in bullet points.

6 6

Isotopes

Isotopes are different varieties of the same element.

Isotopes have:

the same __________________ but different _______________

or the same number of ___________ but different numbers of _______

Carbon is an element that has 2 isotopes called carbon-12 and carbon-14

Carbon-12 Carbon-14

Number of:

protons =

neutrons =

electrons =

Important:

The neutrons do not affect the __________________________ of an element so

different _____________________ of an element perform EXACTLY THE SAME

chemical reactions they are just heavier.

Task

Hydrogen has 3 isotopes. They have mass numbers of 1, 2 and 3. Calculate the

number of protons, neutrons and electrons for all 3 different isotopes of

hydrogen.

CC12 14

Scientists use isotopes to carbon-date dinosaur bones and other fossils.

Compounds

An element is a substance which:

1.

2.

A compound is a substance that contains at _____ or more _________

chemically bonded together.

You must be able to identify the elements in a compound from its formula,

using a periodic table

e.g. CuSO4 contains: _____ atom of the element copper, Cu

_____ atom of the element sulphur, S

_____ atoms of the element oxygen, O

Task

Identify which elements make up the following compounds and how many

atoms of each element there are. The first one is done as an example (it

continues on the next page.

a) MgO

Mg Magnesium – 1 atom

O Oxygen – 1 atom

f) C6H12O6

b) K2O g) Al2O3

c) CO2 h) Fe(OH)2

d) NaOH i) KCr2O7.6H2O

e) P2O5 j) CuSO4.5H2O

Electronic Structure

The electronic structure shows us how electrons are arranged in an atom.

Electrons occupy the space around the _______________.

Electrons ___________ the nucleus in _____________ (sometimes called energy

levels).

Electrons must fill the ________ shell, which is closest to the nucleus before

they can start to fill the _______ shell.

The 1st shell can hold a maximum of _____ electrons

The 2nd shell can hold a maximum of _____ electrons

The 3rd shell holds a maximum of _____ electrons before starting the 4th

shell.

e.g. sodium has 11 electrons so the electronic arrangement for sodium is:

Calcium has 20 electrons so the electronic arrangement for calcium is:

For your exam:

You must be able to deduce the electronic structure of the first 20

elements in the periodic table e.g. calcium is 2.8.8.2.

Element Atomic

Number

Electronic Structure Group

Number

H 1 no

number

He 2

Li 3

Be 4

B 5

C 6

N 7

O 8

F 9

Ne 10

Na 11

Mg 12

Al 13

Si 14

P 15

S 16

Cl 17

Ar 18

K 19

Ca 20

What do pattern do you notice in the number of electrons in the outer shell and the group number of each element?