Atoms, Molecules, Compounds

 All matter is composed of elements, which are made up of atoms that contain protons, neutrons, and electrons. Atoms can combine to form molecules, and these molecules can interact to form cells, tissues, organs, and entire multicellular organisms. Each element has a unique atomic number and mass number, which are determined by the number of protons and neutrons it contains. Isotopes are different forms of the same element that have the same number of protons, but a different number of neutrons. Carbon-14 is a radioisotope that is used to age formerly living objects, such as fossils, through a process called carbon dating.

Atoms, Molecules, Compounds

• Elements are composed of atoms, which are the smallest component of an element that retains all of the chemical properties of that element.
• Atoms are made up of protons, electrons, and neutrons. Protons are positively charged particles that reside in the nucleus of an atom, while electrons are negatively charged particles that travel in the space around the nucleus. Neutrons are neutral particles that reside in the nucleus of an atom. 
• Each element contains a different number of protons and neutrons, giving it its own atomic number and mass number.
• The mass number is defined as the total number of protons and neutrons in an atom. The atomic number is the number of protons in the nucleus, while the mass number is the total number of protons and neutrons in the nucleus.The atomic number is equal to the number of protons, while the mass number is the number of protons plus the number of neutrons. It is possible to determine the number of neutrons by subtracting the atomic number from the mass number.
• Isotopes are different forms of the same element that have the same number of protons, but a different number of neutrons. Some isotopes are unstable and will lose protons, other subatomic particles, or energy to form more stable elements. These are called radioactive isotopes or radioisotopes.
• Compounds are formed when atoms of different elements combine in specific ways to form molecules. In multicellular organisms, molecules can interact to form cells that combine to form tissues, which make up organs. These combinations continue until entire multicellular organisms are formed.
• Carbon-14 is a naturally occurring radioisotope that is created in the atmosphere by cosmic rays. When an organism dies, it is no longer ingesting Carbon-14, so the ratio of Carbon-14 to Carbon-12 will decline. Carbon-14 decays to Nitrogen-14 by a process called beta decay, with a half-life of approximately 5,730 years.
• Carbon dating is the process of determining the age of formerly living objects, such as fossils, by measuring the amount of Carbon-14 remaining in the object and comparing it to the initial concentration in the atmosphere. Isotopes with longer half-lives, such as potassium-40, are used to calculate the ages of older fossils. Carbon dating allows scientists to reconstruct the ecology and biogeography of organisms living within the past 50,000 years.