History of science

and the periodic table

Year 10 Chemistry

Revision Program – History of science and the periodic table

History of science and the periodic table

Objectives Resources on eLearn Text References

� Recognise that the development of the

periodic table was dependent on

experimental evidence at the time

Elements.pptx

Atomic structure part 1.pptx

Ch 2, p. 36

Ch 3, p. 72

� Explain that scientific understanding,

including models and theories, are

contestable and are refined over time

through a process of review by the

scientific community

In ancient times, scientists believed that all matter was made of four elements – Earth, Air, Fire and

Water.

This is very far from our belief now!

In modern times, we know that all matter is made of almost one

hundred naturally occurring elements, which are organised (in order

of their atomic number and according to their chemical properties)

on the periodic table. The first one was made by Dmitri Mendeleev.

Research into new elements (made in nuclear reactors) is ongoing.

There are now 114 elements on the table (the latest being two are

Livermorium and Flerovium – what hideous names!).

History of science

and the periodic table

Our beliefs about matter have changed in other ways, too. In ancient Greece, the preeminent thinker

Aristotle believed the four-element theory, and thought that matter was continuous, and could be

forever divided. However, another philosopher, Democritus, was the first to suggest that all matter was

made of atoms: tiny, indivisible particles that were constantly moving.

In the 1800s, Dalton formulated his Atomic Theory, which added a few important ideas:

• Atoms of one element are identical to each other;

• Atoms of one element are different from the atoms of all other elements;

• Atoms cannot be subdivided or destroyed (but, in chemical reactions, they can combine or

separate).

It is important to note, though, that the atom is not, in fact, the smallest possible particle! Atoms are

made up of electrons (outside the nucleus) and protons and neutrons (inside the nucleus). Protons are

made up of smaller particles still – quarks, for example.

Now, scientists know that atoms can be divided by nuclear reactions (as opposed to chemical reactions).

These happen in nuclear reactors, such as the one operated by

the Australian Nuclear Science and Technology Organisation

(ANSTO) at Lucas Heights in Sydney. These reactors are very

important in making radioisotopes, which are used in research

and medicine (as radiopharmaceuticals). Isotopes and

radioisotopes are discussed in Revision Topic 2.

History of science

and the periodic table

A summary in comic form:

History of science

and the periodic table

Review questions

1. On the periodic table, atoms are listed in order of their ___________ ____________.

2. Atoms can be divided by ___________ ____________.

3. The following comic shows a light-hearted look at the search for evidence for sub-atomic particles

(particles that are smaller than the atom).

Name a particle that is smaller than a proton.

____________________________________________