General Chemistry

• Matter is composed of tiny particles called atoms.
• Atom: smallest part of an element that is still that element.
• Molecule: Two or more atoms joined and acting as a unit.
• Use subscripts when more than one atom is in the molecule.
• Chemical reaction: One substance changes to another by reorganizing the way the atoms are attached to each other.
• Atoms


  Building blocks of elements
• Similar atoms in each element
• Different from atoms of other elements
• Atoms


  • Two or more different atoms bond in simple ratios to form compounds
• Atomic Number: This refers to how many protons an atom of that element has. No two elements, have the same number of protons.
• All atoms of an element have the same number of protons
• Mass Number = counts the number of protons and neutrons in an atom
• An atom is neutral
• The net charge is zero
• Number of protons = Number of electrons
• Atomic number


  Number of electrons
• Isotopes: Atoms with the same number of protons but different numbers of neutrons. Show almost identical chemical properties; chemistry of atom is due to its electrons. In nature, most elements contain mixtures of isotopes.
• While most atoms have the same number of protons and neutrons, some don’t
• Some atoms have more or less neutrons than protons. These are called isotopes.
• An atomic mass number with a decimal is the total of the number of protons plus the average number of neutrons.
• Isotopes - Atoms with the same number of protons, but different numbers of neutrons. Atoms of the same element (same atomic number) with different mass numbers.