Atoms & Atomic Structure - An atom is the smallest piece of an element - are composed of three types of sub-atomic particles: protons, neutrons & electrons Nucleus = central portion of atom - small and dense (little empty space) - gives an atom its mass (atomic weight) - composed of: a) protons: positively (+) charged particles b) neutrons: neutral particles (no charge) Electron Cloud = surrounds the nucleus - composed of electrons :negatively charged particles which orbit the nucleus in energy levels - the number of protons and electrons are always equal in a neutral atom (PEN) = the positive and negative charges are equal and balance each other out. Representing Atoms: Bohr Diagrams and Lewis Structures Information about atoms can be obtained from the periodic table: You may see the information written this way: 1 atomic number = # of protons H 1.01 atomic mass = # of protons + # of neutrons # of neutrons in an atom = atomic mass - # of protons - Atoms can be represented in different ways:
Bohr Diagrams - are used to show how many electrons appear in each energy level or electron shell around an atom. - the # of protons & # of neutrons is written to represent the nucleus - energy levels (circles) are drawn around the nucleus - each shell (energy level)can only hold a certain number of electrons: : the first orbit (nearest the nucleus) = 2 electrons : the second holds 8 : the third is also full when it has 8 electrons. - the number of shells corresponds to the period number of the element Electron Dot Diagrams - The electrons in the outermost shell (valence shell) are called the valence electrons.
- Elements in each chemical family have the same number of valence electrons - # of valence electrons = group # in metals & non-metals (transition metals have 1, 2, or 3) - This can be shown using an Electron Dot Diagram also called a Lewis Diagram - use the symbol of the element to represent the nucleus and inner shell electrons - Valance shell electrons are then shown as dots placed around the symbol in the pattern of a square. Li F Al Lewis dot diagrams for lithium, fluorine, and aluminum.
Atoms and Atomic Structure - An atom is the smallest piece of an - are composed of three types of sub-atomic particles: protons, neutrons & electrons Nucleus = central portion of atom - small and dense (little empty space) - gives an atom its mass (atomic weight) - composed of: a) protons: charged particles b) neutrons: neutral particles Electron Cloud = surrounds the nucleus - composed of electrons : charged particles which orbit the nucleus in - the number of protons and electrons are always equal in a neutral atom = the positive and negative charges balance each other out. Representing Atoms: Bohr Diagrams and Lewis Structures Information about atoms can be obtained from the periodic table: You may see the information written this way: 1 atomic number = H 1.01 atomic mass = + # of neutrons in an atom = atomic mass - # of protons - Atoms can be represented in different ways:
Bohr Diagrams - are used to show how many appear in each energy level or electron shell around an atom. - the # of protons & # of neutrons is written to represent the - energy levels (circles) are then drawn around the nucleus - each shell can only hold a certain number of electrons: - the first orbit (nearest the nucleus) = electrons - the second hold - the third is also full when it has electrons. - the number of shells corresponds to the period number of the element Electron Dot Diagrams - The electrons in the outermost shell (valence shell) are called the
- Elements in each chemical have the number of valence electrons - # of valence electrons = in metals & non-metals (transition metals have 1, 2, or 3) - This can be shown using an Electron Dot Diagram also called a Lewis Diagram - use the symbol of the element to represent the - Valance shell electrons are then shown as placed around the symbol in the pattern of a square. Li F Al Lewis dot diagrams for lithium, fluorine, and aluminum.