Unit 6, Lesson 7: The Electronic Nature of Chemical Bonding

Why are the “young men” being attracted toward the window? What would happen if they were separated by a greater distance? Who would be more attractive – a -1 or -2 charge lady?

Electrostatic Forces An electrostatic force is a force of attraction or repulsion between two charged particles. Opposite charges attract and like charges repel. The greater distance between particles, the smaller electrostatic force between them. The greater charge on particles, the greater electrostatic force between them.

Electron Shells Each period (row) in the periodic table corresponds to an electron shell. Going down the periodic table, the _____ shells an atom has, and the _____ the atom is. Going left to right, the atomic number increases, so the positive charge in the nucleus _____, and the _____ the electrostatic force between the electrons and protons, so the atoms get _____. Give time to fill in blanks, then discuss.

Electron Shells (continued) A closed shell has the same number of electrons as a noble gas. An open shell does not.

Brain Break!

Valence Electrons Valence electrons are electrons in open shells. Count them by counting left to right in the row of the atom, skipping transition metals. Noble gases have zero valence electrons.

Valence Electrons (continued) For ions, add one valence electron for every _____ charge and subtract one for every _____ charge. If the result is the same number as a noble gas, then there are ____ valence electrons.

The Valence of an Atom The valence of an atom is the number of unpaired electrons it has. Considering that: a) valence electrons have four different orbitals to fill (one s and three p – we ignore transition metals and thus d), and b) they fill empty orbitals before pairing up, find the valence of each atom from Li to Ne.

People and electrons – not so different:

Ionization Energy Ionization energy is the energy required to remove an electron from a neutral atom. Going down the periodic table, valence electrons are _____ the nucleus, so ionization energy _____. Going left to right, valence electrons are _____ the nucleus, so ionization energy _____.

Practice Pg. 170 #53 and 55 5 min