2. Chemistry Review.pdf - Untitled Document 1 of 5 https/lms.virtualhighschool.com/content/OSSD-v2/Department/Scien Listen Chemistry Review The Atom An

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Chemistry Review The Atom An atom is made up of a very small nucleus that contains positively charged subatomic particles called protons and subatomic particles without charge called neutrons . Around the nucleus there are negatively charged electrons traveling in defined orbital paths. The atomic number of an element is equal to the number of protons in the nucleus of an atom. We can use this number to determine the number of electrons in orbitals around the atom as it must be the same as the number of protons in a neutral atom. This number is always a whole number. The atomic mass is equal to the number of protons and neutrons in the nucleus. Electrons are so small that their mass is negligible. When you are studying the periodic table you will notice that the atomic mass of each element is not a whole number. This is because in nature each element exists in different forms with varying numbers of neutrons. These forms are called isotopes . For example, a sample of carbon will contain 98.9% carbon-12 and 1.1% carbon-13. The carbon-12 atom has 6 protons and 6 neutrons, whereas, carbon-13 atom has 6 protons and 7 neutrons. The charge on the atoms remains the same as neutrons carry no charge but the mass of carbon-13 will differ due to the weight of the extra neutron. All of the elements of the earth are organized in the periodic table in order of increasing atomic number. An element is a substance that is made up of only one type of atom, all of which have the same atomic number. The main elements of the human body are carbon, oxygen, hydrogen, and nitrogen.
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