The terms element, atom, electron, proton and neutron are likely familiar.
An element is any substance that cannot be decomposed into substances with different properties.
Although there are more than 100 elements, living things are made up mostly of just 6 of them:
carbon, hydrogen, oxygen, nitrogen, sulfur, and phosphorus. In addition, magnesium, iodine, iron,
calcium, and a few other elements are also found in living organisms but in much smaller amounts.An atom. is the smallest unit of matter that is unique to a particular element.
Atoms are composed of three particles: protons, neutrons, and electrons. The nucleus of an atom contains neutrons and protons.
Protons are found at the center or nucleus of an atom. They have a positive charge. The number of protons in an atom is called the atomic number. Each element has a unique atomic number. All atoms of an element have the same number of protons.
Neutrons are also a part of the nucleus. They are neutral (have no charge). Isotopes are forms of an element whose nuclei have the same atomic number - the number of protons in the nucleus - but different mass numbers because they contain different numbers of neutrons. The atomic mass is composed of protons plus neutrons.
Electrons have a negative charge. Their quantity is equal to that of the protons. They move around the nucleus in orbitals.
Atomic numbers and mass numbers give us an idea of whether and how substances will react.
REVIEW: Electrons carry (a) ________ charge.
REVIEW: Which is the smallest portion of a substance that retains the properties of an element?
REVIEW: The positive subatomic particle is the
REVIEW: The atomic number refers to the
REVIEW: The atomic weight (or mass) of an atom is determined by the weight of
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