Chapter U1.11, Problem 1TAI

Interpretation Introduction

Interpretation: Smallest bits of matter are to be described.

Concept Introduction: Matter is anything that has mass and occupies space. A matter is made of elements and compounds which can be imagined to be made of still smaller particles. These small particles of matter cannot be seen with the naked eye. Millions of small particles make up a small part of the matter.

Answer to Problem 1TAI

1. Long ago philosophers like Democritus proposed that all matter was composed of tiny particles that could not be further divided.
2. These small particles were later known as atoms. Atoms cannot be seen as they are very small.
3. In 1803 a scientist called Dalton gave an atomic theory to describe the structure of an atom.
4. The atomic theory states that all matter is made of atoms.
5. Since at the Dalton’s time many scientists have created different models to describe atoms and sub- atomic particles.
6. An atom has a nucleus made of protons and neutrons, with electrons revolving around the nucleus.

Explanation of Solution

Matter is made of small bits of particles called atoms. In 460 B.C.E Greek philosopher Democritus was the first one to suggest that every matter can be broken down to its smallest bit which cannot be further divided. This concept was not backed by any evidence so it was not given any importance. These small particles were later called atoms.

Later in 1803, British scientist John Dalton suggested that atoms can explain how elements combine in specific ratios to form a compound. He gave an atomic theory according to which all matter is made of atoms. He conducted several experiments to support his idea. His theory helped in making accurate predictions about behavior of matter.

Since Dalton’s time many scientists have created different models to describe atoms and sub- atomic particles. An atom has a nucleus made of protons and neutrons, with electrons revolving around the nucleus.

The nucleus is in the center of the atom and electrons are outside the nucleus. In a neutral atom, protons are positively charged and electrons are negatively charged.

Conclusion

Long ago, philosophers imagined that matter was made of small particles called atoms. Over several years scientists provided evidences to create several models of atom. An atom is basically made of still smaller particles called electrons, protons and neutrons.