TEKS 8.5A Atom: The building block of matter; the smallest component of an element that maintains the properties of that element Subatomic Particle Charge Size Location Positive (+) 1 amu Nucleus Neutral 1 amu Nucleus Negative Too small to count Outside Nucleus Electron Cloud Protons are held inside the nucleus by a force called the STRONG force. Proton Neutron Electron The charge of an atom’s nucleus is always positive due to the presence of the prootons. D. Energy Levels: The rings surrounding the nucleus that hold the electrons in a Bohr diagram; also called orbitals, electron shells An atom with a charge is called an ION B. Neutrons: Neutrally charged subatomic particles located in the nucleus; add mass to the atom E. Electrons: Negatively charged subatomic particles; Located in the electron cloud; Mass does not affect the mass of the atom A. Protons: Positively charged subatomic particles; located in the nucleus; add mass to the atom; same as the atomic number; provide identity of the atom Protons are the identity of an atom! A subatomic particle is one of three main parts inside of an atom- protons, neutrons, and electrons C. Nucleus: The center of the atom that holds the mass of the atom; contains protons and neutrons Energy Level Max # of Electrons 1st 2 nd 2 8 3rd 8 / 18 When the numbers of protons and electrons are equal, the charge of the atom is NEUTRAL. ©DesignedbyK.Blackstock The mass of the atom is located in the NUCLEUS Most of the volume of the atom is Empty Space Mass – Protons = Neutrons • • I must know/be able to: -Describe the structure of atoms, including the masses, electrical charges, and locations, of protons and neutrons in the nucleus and electrons in the electron cloud. Atoms are the smallest particles of an element. Each element is made of only one kind of atom. For example, gold is only made of gold atoms and neon is only made of neon atoms. The overall shape of all atoms is spherical (like a basketball), but they vary in size. Each atom has a nucleus located at its center, surrounded by an electron cloud, which is mostly empty space outside of the nucleus. The nucleus is very small compared with the overall size of the atom. • • • Atoms are made of three different kinds of subatomic particles: protons, neutrons, and electrons. All of an atom’s protons and neutrons are tightly packed together in the atom’s nucleus. The nucleus is held together by the strong nuclear force, which is stronger than the electromagnetic force that otherwise would cause like-charged protons to repel one another. Protons have a positive (+) charge, and each has a mass of one “atomic mass unit” (amu). • • • Neutrons have neutral (sometimes stated as a neutral or zero (Ø) charge), and each has a mass of 1 amu. Electrons have a negative (-) charge, and a very tiny mass of 0.005 amu. The mass of electrons are so small that they are ignored when adding up the mass of the entire atom to state the atom’s atomic mass. All of the atom’s electrons are located somewhere in the electron cloud. It is not possible to know exactly where the electrons of an atom are located. It is useful to think of electrons as orbiting the nucleus much as planets orbit the Sun (as shown in the Bohr Model), though electrons do not really have separate defined orbits. # Protons = Atomic Number • • • • Atomic Mass = Protons + Neutrons BOHR MODEL ELECTRON CLOUD MODEL Atoms of a particular element have a set number of protons. For example, every atom of hydrogen has one proton and every atom of gold has 79 protons. The number of protons is called the element’s atomic number. Atoms that are electrically neutral will have the same number of protons and electrons. If an atom has an electrical charge, it is because it has more or less electrons than its’ number of protons. In this case, the atom is called an ion. Not all atoms of the same element will have the same number of electrons and/or neutrons Atoms of an element with different numbers of neutrons are called isotopes of that element. So, atoms of a particular element can have different atomic masses. The total number of protons and neutrons in an atom’s nucleus is called the atomic mass of that atom. ©DesignedbyK.Blackstock