The ancient Greeks coined the term atomos, meaning the smallest possible separation of matter. In ancient times, both the Greeks and Indians had philosophised about the existence of the atom. However, it was first hypothesised scientifically by the British chemist John Dalton in the early years of the 19th century,A_________________. Since then, smaller subatomic particles have been discovered and the part they play as the basic building blocks of the universe is clear. We now know that atoms are made up of differing numbers of electrons, neutrons and protons, and these too are made up of even smaller particles. Daltons theory about atoms was not immediately accepted by chemists, although one reason for this was Daltons well-known carelessness in experimental procedures. However, we know that Dalton was correct in almost everything he said in his theory of the atom. He described an atom, even though he had never seen one,B_______________. It could combine with the atoms of other chemical elements to create a compound. Almost a century later the first subatomic particles were discovered. By the 1930s, physicists were working with new ideasC__________________. In turn, these developments helped them to develop quantum mechanics. In chemistry, the atom is the smallest part of an elementD________________. The difference in the number of subatomic particles makes one atom different from another. Subatomic particles also have another purpose. If there is the samenumber of electrons and protons in the atom,E__________________. A difference between the two means the atom has an electrical charge. In other words, it produces electricity. This electricity means the electrons can become attracted to each other. In this way, atoms can bond together to form molecules, and when enough molecules are joined together we have matterF__________________ . 1.when he suggested it was the smallest particle that could exist 2.that we can see 3.as he has no equipment 4.as a particle that cannot change its nature 5.then it will be electronically neutral 6.that can still be recognised 7.which allowed them to investigate the parts of the atom in great detail