Atomic Structure
Subatomic Particles
- Neutron = Large with no charge; location=nucleus
- Proton = Large with positive charge; location=nucleus
- Electron = small with negative charge; location=cloud surrounding the nucleus - A neutral atom has no overall net charge.
Atomic Number: The Proton Number
- found in the nucleus of an atom
- has no overall electric charge
Atomic Number = # of protons - # of electrons
Ions
- Atoms that have gained or lost electrons are called Ions
- Most atoms are capable of either gaining or losing electrons. A few elements, like hydrogen, are able to do both -- by accepting electrons from or giving electrons to, either atoms.
- An ion is an electrically charged atom.
- Negatively-charged ion: anion = when electron are added to a neutral atom
- Positively-charged ion: cation = when electron are subtracted to a neutral atom
Mass Number
- is the number of protons and neutrons or atomic mass number since atomic # = the # of neutrons
- Atomic mass ≠ # of protons + #of neutrons
- Number of neutrons = Mass number - protons
Atomic Mass
- The average mass of an element's isotopes
- since most of the mass of an atoms is concentrated in the protons and neutrons located in the nucleus.
- If a neutron is added to an element's nucleus, a heavier version of the same element (isotope) will be produced.
Isotopes
- are atomic species having the same atomic number (protons) but different atomic masses/mass numbers (neutrons)
