Compounds are made of different kinds of atoms that are chemically joined, as if they've been pounded together. What is the difference between Elements and Compounds? Mixtures Vs. However, the protons and neutrons in the nucleus are attracted to each other by a different force, called nuclear force, which is usually stronger than the electromagnetic force repelling the positively charged protons from each other. The reason for this is their instability due to which they undergo radioactive decay over a period of time giving rise to new elements during the process like Uranium, Thorium, Bismuth etc. The smallest unbreakable unit of a compound is called a molecule . We use a symbol to represent an element, whereas … Elements cannot be broken down into simpler substances by chemical reactions. Elements contain only one type of atom. Compounds are almost endless. There can be different ratios of compounds (more of one element than the other).. There are about 117 elements that have been observed. Metals are shiny and good conductors of electricity and heat. One of the simplest is called methane, in which there are always four times as many hydrogen particles as carbon particles. Compounds can form only in chemical reactions, and they can break down only in other chemical reactions. Matter is defined as anything that has mass and volume. A chemical substance has a definite composition and the same composition throughout. A pure substance can be classified as either: (i) an element (ii) a compound .