The Atom as we know it (via the Atomic Theory) And so… How do we teach others the arrangement of the subatomic particles?

The Atomic Theory all matter is made of atoms explains what atoms look like, and how and why they behave the way they do see past notes for previous atomic theories (Dalton, Thomson, Rutherford)

Atomic Regions and Parts (e-) Electrons (Electron Cloud): each has a (-1) charge little to no mass located outside of the nucleus Nucleus dense, (+) mass in the atom’s center (p+) protons each has a (+1) charge has a mass of 1 a.m.u. (atomic mass unit) (n) neutrons no charge But this image doesn’t do enough to explain exactly where the electrons are or what the electrons are doing. How can we give more clarification about the electrons?

The Bohr Model of the Atom The Electron Cloud: the region of the atom where electrons are located occupies most of the atom’s volume (space) divided into energy levels (see picture below) Nucleus First Energy Level: Can hold 2 e- Second Energy Level: Can hold 8 e- Third Energy Level: Can hold 18 e- Fourth Energy Level: Can hold 32 e-

**New Terms** Valence Electrons Energy Levels The following terms are used to describe characteristics or locations of electrons Valence Electrons e- in the outermost energy level could be in any energy level determine chemical properties  Energy Levels The “rings” indicating how the “distance” and electron is from the nucleus e- can move from one energy level to the next by absorbing or releasing energy ex: excited electrons absorb energy and move to higher energy levels

Wow – there’s a lot of information here! Neils Bohr discovered the energy levels in the electron cloud Electrons could jump energy levels Looked like the solar system So far the Periodic Table gives us the following information about an element: # of Protons from the atomic number # of total e- also from the atomic number (in neutral atom) # of energy levels from the Period (row #) # of valence e- from the Group (column #) And the # of Neutrons can be calculated once we know the mass # # N = mass # - atomic #

Let’s try a Bohr model of Potassium (K-41) ____ N ___ e- ___ e- e- e- ___ e- e- There will be 19 electrons total Atomic number is 19 2 8 P=19 N= 22 8 1 This is the where the valence electrons go Let’s try a Bohr model of Potassium (K-41) 1) Draw the Nucleus and enter: A. # P (= Atomic #) B. #N (= mass # - #P) 2) Determine the Total # e- (= #P) 3) Determine the # of energy levels and draw them (= Period or row#) 4) Enter the # of valence e- in the last energy level (= Group or column#) 5) Fill in the inside energy levels with electrons, starting at the first and working out, ending with the second to last energy level using up the remaining e-. Remember: 1st energy level holds up to 2 e- 2nd energy level holds up to 8 e- 3rd energy level holds up to 18 e- 4th energy level holds up to 32 e- Potassium is in group 1A = 1 valence electron

This has been an example of a Bohr model using a NEUTRAL atom the smallest piece of an element in which there is no charge an atom with the same number of protons and electrons # protons = # electrons How many protons? How many neutrons? 12 C 6 How many electrons? 6 6p 6n How many energy levels? 2 4 2 How many on the last (2nd ) energy level? How many on the first energy level?