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Matter is a substance made up of various types of particles that occupies physical space and has mass. According to the principles of modern physics, the various types of particles each have a specific mass and size.
The most familiar examples of material particles are the electron, the proton and the neutron. Combinations of these particles form atoms.
Atoms, Molecules, Elements and Compounds
Fundamentally, matter is composed of elementary particles called atoms.
A combination of atoms forms a molecule. Large groups of atoms and molecules form the bulk matter of day-to-day life in the physical world. There are more than 100 different kinds of atoms listed in the periodic table, with each kind constituting a unique chemical element.
Atoms and/or molecules in two or more elements can join together to form a compound. This compound, which is the basis of matter, may not resemble any of the original ingredients.
For example, sodium and chlorine, two highly poisonous elements that are unstable at room temperatures, combine to form one of the most common and harmless compounds known to man called common salt (sodium chloride, or NaCl). Unlike its constituent elements, salt is highly stable, harmless to humans and even edible.
Similarly, hydrogen and oxygen, which are both gaseous elements can combine to form water, which is a liquid compound, not a gas, at room temperature.
The process by which such combinations and transformations of elements into compounds take place is called a chemical reaction.
Protons, Electrons and Neutrons In Matter
All matter consists of atoms, which, in turn, consist of protons, neutrons and electrons. Both protons and neutrons are located in the nucleus, which is at the center of an atom. Protons are positively charged particles, while neutrons are neutrally charged. Electrons are negatively charged, and they exist in orbitals surrounding the nucleus.
In any atom, like charges repel one another, and opposite charges attract one another. This is why two protons repel each other and so do two electrons, but a proton and an electron attract each other.
In an element, the numbers of electrons and protons are equal. Moreover, since they have opposite charges, they cancel each other out and keep the atom neutral.
The total number of protons present in the atom of a substance is known as the atomic number. Atomic mass refers to a weighted average of the number of neutrons and protons in the atom. The number and mass for each type of atom is listed in the periodic table.
When a chemical reaction takes place to combine two or more electrons into one or more compounds, the electrons of the atoms of each element interact with each other. However, the reaction does not affect the atoms’ nuclei.