AQA-8462-HODDER-SAMPLE

1 Atomic structure and the periodic table
Isotopes have a different mass, but their chemical properties are the
same because they contain the same number of electrons.
Test yourself
5 List the three particles found inside atoms.
6 Identify the particle found inside the nucleus of atoms that has no charge.
7 Atoms contain positive and negative particles. Explain why atoms are
neutral.
8 How many protons, neutrons and electrons are there in an atom of 31 P?
9 What is it about the atom 39 K that makes it an atom of potassium?
10 Describe the similarities and differences between atoms of the isotopes
35 Cl and 37 Cl.
Show you can...
Copy and complete the table for each of the elements listed.
Element
7 Li
Atomic
number
Mass
number
Number of
protons
Number of
electrons
Number of
neutrons
27 Al
24 Mg
39 K
107 Ag
● Electron arrangement
The electrons in an atom are in energy levels, also known as shells.
Electrons occupy the lowest available energy levels. The lowest energy level
(the first shell) is the one closest to the nucleus and can hold up to two
electrons. Up to eight electrons occupy the second energy level (the second
shell) with the next eight electrons occupying the third energy level (third
shell). The next two electrons occupy the fourth energy level (fourth shell).
The arrangement of electrons in some atoms are shown in the table. The
electronic structure can be drawn on a diagram or written using numbers.
For example, the electron structure of aluminium is 2,8,3 which means
that it has two electrons in the first energy level, eight electrons in the
second energy level and three electrons in the third energy level.
Atom He F Al K
Atomic number 2 9 13 19
Number of
2 9 13 19
electrons
Electron structure 2 2,7 2,8,3 2,8,8,1
(written)
Electron structure
(drawn)
6