Ch.3 - Atoms and Bonding
Standards covered in this chapter:
7.PS1.1 - Develop and use models to illustrate the structure of atoms, including the subatomic particles with their relative positions and charge.
7.PS1.2 - Compare and contrast elemental molecules and compound molecules.
7.PS1.5 - Use the periodic table as a model to analyze and interpret evidence relating to physical and chemical properties to identify a sample of matter.
Important Vocabulary:
Atom - the basic particle from which all elements are made; the smallest particle of an element that has the properties of that element.
Electron - A tiny, negatively charged particle that moves around the outside of the nucleus of an atom.
Protons - Small, positively charged particles that are found in the nucleus of an atom.
Nucleus - The central core of an atom which contains protons and neutrons.
Neutron - A small particle in the nucleus of the atom, with no electrical charge.
Atomic Number - The number of protons in the nucleus of an atom.
Isotope - An atom with the same number of protons and a different number of neutrons from other atoms of the same element.
Mass Number - The sum of protons and neutrons in the nucleus of an atom.
Valence Electrons - The electrons that are in the highest energy level of an atom and that are involved in chemical bonding.
Chemical Bond - the force of attraction that holds two atoms together.
Summary
At the center of the atom is a tiny, dense nucleus containing protons and neutrons. Surrounding the nucleus is a cloudlike region of moving electrons. When a neutral atom loses or gains a valence electron, it becomes and ion. The number of valence electrons in each atom of an element helps determine the chemical properties of that element. Unequal sharing of electrons causes bonded atoms to have slight electrical charges. A metal crystal is composed of closely packed, positively charged metal ions. The valence electrons drift among the ions. Atomic theory grew as a series of models that developed from experimental evidence.
Atoms are the smallest particles that can still be considered elements.
Electron dot diagrams include the symbol for the element surrounded by dots. The dots represent the valence electrons.
