The Structure of an Atom

Atoms All atoms are made up of protons, neutrons and electrons- these are subatomic particles Protons are positively charged particles found in the nucleus of an atom Neutrons are neutral particles also in the nucleus of an atom Electrons are negatively charged particles that orbit around the nucleus in an electron cloud These subatomic particles can be distinguished by mass, charge and location in an atom

Atomic Number and Mass Number Atomic Number- the number of protons in an element Atomic # identifies an element Atoms of different elements have different atomic numbers Since elements are electrically neutral, the # of protons equals the # of electrons Mass Number- total number of protons and neutrons in an element p+ + n0= mass number

Isotopes In Dalton’s atomic theory, all atoms of a given element are the same They have the same number of protons and electrons Atoms of the same element can have different number of neutrons – these are called isotopes Same atomic number, different mass number

Reading Information on Periodic Table Atomic Number Symbol Name 6 C Carbon 12.011 *Memorize* Atomic # = # of protons # of protons = # of electrons Atomic mass = # of protons + # of neutrons Average Atomic Mass Why is the mass of carbon a decimal?

Practice What is the atomic number of Li? How may electrons are in Li? What is the mass number? How many neutrons are in Li? 3 Li Lithium 6 Look at the periodic table in the back of you book: What is the name of an element that has 47 protons?

With your partner Pg 112 in your book #8 and 9 Hand in