Electrons (e - ’s) and Orbitals Be sure to keep up on your reading from your text and studying your notes (scientific method, sigfigs, sci. notation, electron configs, models, etc.). A quiz may be right around the corner… Or not… Or yes… Hint hint.

 Several models were created to explain the properties observed by the atom. ◦ The charges of the electrons ◦ The charges of the protons ◦ The size, locations, and arrangement  Originally, scientists believed (chronologically) 1.Solid-Sphere Model (Plum Pudding Model) 2.Planetary Model (Rutherford’s Model) 3.Quantum Model (WHAT WE KNOW TODAY)

 Rutherford’s model proposed electrons orbit the atom ◦ This proved J. J. Thompson’s “Plum Pudding Model” was incorrect ◦ States electrons orbited the atom like moons to a planet  Bohr’s model confines e - ’s to energy levels ◦ States e - ’s can only be certain distances from the nucleus ◦ This distance depends on the energy the e - has ◦ The further away, the higher energy level

 The present-day model of the atom, in which electrons are located in orbitals, is also known as the quantum model ◦ States electrons within an energy level are located in orbitals, regions of high probability for finding a particular electrons. ◦ Does not, however, explain how the electrons move about the nucleus to create these regions

 According to the current model of the atom, electrons are found in orbitals ◦ -regions around the nucleus that correspond to specific energy levels ◦ Orbitals are sometimes called electron clouds because they do not have sharp boundaries ◦ Tells where it is likely to find an electron

 Pauli Exclusion Principle ◦ The principle that states that two particles of a certain class cannot be in the exact same energy state  Electron Configuration ◦ the arrangement of electrons in an atom  Aufbau Principle (German for “building up”) ◦ States that electrons fill orbitals that have the lowest energy first!!

 “Building up” refers to the filling of all lower energy “sites” before increasing up in energy  Moving outward away from the (+) nucleus requires more energy for the (-) electrons to maintain the further distance  We have 4 orbitals (spots) that e - ’s can go into: ◦ s-orbital (holds ________)d-orbital (holds ________) ◦ p-orbital (holds ________)f-orbital (holds ________)

 Write out the electron configuration for an element with an atomic number of 20 Atomic # = # of protons = # of electrons 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 We can abbreviate this using the LAST noble gas i.e. [Ar] 4s 2

 Write the electron configuration for an atom of an element whose atomic number is 8.  Write the electron configuration for an atoms of an element whose atomic number is 34.  Write out the electron configuration for Copper.

 Draw these out.  Electrons MUST fill the lower energy levels before moving to the next. Each level is increasing energy.

 If an electron is in a state of lowest possible energy it is in the Ground State  If an electron gains energy, it moves to an Excited State  An electron in an excited state will release a specific amount of energy as it “falls” back down to the ground state. ◦ This energy is emitted as certain wavelengths of light

 Atomic Mass ◦ The mass of an atoms expressed in atomic mass units (AMU)  The Mole!! ◦ A mole is just a counting unit (a quantity) for really small things (like atoms) ◦ It is x of anything ◦ This value is known as Avogadro’s Number

 Molar Mass ◦ The mass in grams of one mole of the element ◦ Has the units of g/mol  1 mole has 6.022x10 23 atoms (particles)  Avogadro’s Number allows us to CONVERT between moles and grams

 Calculate the molar mass of NH 3  Calculate the molar mass of H 2 SO 4  Calculate the molar mass of NaCl

 Convert 12.5 grams of LiOH to moles LiOH  Convert 0.58 moles of H 2 O to atoms of water  Convert 1.28 moles of cobalt(II)oxide to mass

 Counting Atoms and Electron Configuration Worksheet  Work on:  e- config for Mn, Fe, and Co  Convert: ◦ 1.85 mol Al  g ◦ 8.9 g O  mols