The Structure of the Atom

Inside the Atom  Atoms are made of subatomic particles.  Protons  Neutrons  Electrons  Protons and neutrons are in the nucleus.  Electrons are found surrounding the nucleus.

Protons & neutrons  Contribute to most of the mass of the atom.  Each is 1840 times the mass of electrons.  Neutrons have no charge  Neutrons and protons are attracted through “strong force” attractions.  Protons have a positive charge

 The # of protons in the nucleus of an atom is the atomic number.  Atomic number identifies the atom as a particular element

 EG.  # of protons? 66  Atomic number? 66  element?  Carbon  It will always be carbon! Cannot change.

 If a proton is somehow removed or added, it will no longer be carbon!  The sum of protons and neutrons is the mass number.  Mass # is a whole number, so you will have to round the # found on the periodic table.  EG. Carbon:  Mass = 12  Proton = 6  Neutron = ?  = 6

 The symbols that we use to represent different chemicals are the same in each language, although we do call elements different names.  We use a standard atomic notation to represent elements.  Mass # is written above, atomic # below and the symbol in large letters to the left.

TRY THIS!  On page 189 of your textbook, do activity 5-4.

Bohr-Rutherford models  A way of representing the atomic structure of an element.  Electrons occupy specific energy levels called shells. Electron that are further away from the nucleus have more energy.  You have to fill the shell closest to the nucleus first.  The first shell can only take 2 electrons, the next one can take 8, the 3rd can take 8 also.

How to Draw it?  1. Draw a circle (nucleus) and write the # of protons of that atom next to a “p”. And the number of neutrons next to an “n”.  EG Boron  Proton # = ?  Neutron # = ? 5p 6n

 Step 2: determine the # of electrons in the atom (same as proton #) Draw the energy levels. 5p 6n Electrons: 5

 Step 3: Starting with the closest energy level to the nucleus, put in a max of 2 electrons.  Second level can take a max of 8 electrons  Third level can also take a max of 8.  For boron, we only need two levels. 5p 6n

YOU TRY IT!!  Fill in the Bohr- Rutherford diagrams for the first 20 elements.

Isotopes  One of two or more forms of an element that have the same number of protons but a different number of neutrons.  Since each isotope has a unique mass number, you can specify an isotope of an element by placing its mass number after the name of the element.  EG. Hygrogen-1 and hydrogen-2  Try this: p. 193 #1-8