Chapter 2 Notes The mass of an atom is concentrated in its minute, positively charged nucleus. Chapter 2.1: The nuclear atom

Important Terms for this Section Quantum Theory Elements Atoms Compounds Molecules Sub-atomic particles Electrons Nucleons: Neutrons Protons Mass number Atomic number Isotope Ion Cation Anion Mass spectrometer mass spectrum

Quantum theory Please shorthand note the following: A theory based on the principle that matter and energy have the properties of both particles and waves, created to explain the radiation of energy from a blackbody, the photoelectric effect, and the Bohr theory, and now used to account for a wide range of physical phenomena, including the existence of discrete packets of energy and matter, the uncertainty principle, and the exclusion principle. Ex: theory re: matter and E have particle and wave props. Created explain  rad of E from blackbody photoele. Effect, Bohr thry uncert princ exclusion princ.

elements Substance that cannot be broken down into simpler substances by a chemical reaction Example: different elements have different chemical properties, but the same kind of element may have different physical properties but have similar chemical properties (such as gold dust vs. gold foil)

Dalton: Solid Sphere model of the atom All matter is composed of tiny indivisible particles called atoms Atoms cannot be created or destroyed Atoms of the same element are alike in every way Atoms of different elements are different Atoms can combine together in small numbers to form molecules Result = Solid Sphere Model This helps us understand how elements react to form compounds (balanced reactions and bonding)

J.J. Thompson: Plum pudding model Discovered there are negative charges in the atom = electrons Negative charges embedded in a positive core

Summarized Experiment Voltage Cathode (-) anode (+) http://electronics.howstuffworks.com/tv3.htm Click here Empty glass tube (vacuum) connected to a metal cathode and anode. High voltage is applied to the tube. This caused the atoms in the cathode to get excited. Electrons stream off the cathode, producing a cathode ray. The cathode ray traveled toward the anode

Summarized Experiment Voltage - Cathode (-) anode (+) Click here When a negative charge was brought toward the cathode ray, it caused the cathode ray to move away from the negative charge.

Summarized Experiment Voltage + Cathode (-) anode (+) Click here When a positive charge was brought toward the cathode ray, it caused the cathode ray to move toward the positive charge.

Ernest Rutherford: Nuclear Model Gold foil experiment Results = Positively charged nucleus in center of atom Electrons moving around nucleus at a distance

Atoms gain E = e- move way from nucleus (higher E level) Atoms lose E = e- move toward nucleus (lower E level) & release light Electrostatic force of attraction between p+ and e- prevents e- from leaving atom Neutrons are needed to stabilize larger atoms Energy Added Energy Released e- The resulting hydrogen atoms are excited; that is, they contain excess energy, which they release by emitting light of various wavelengths to produced emission spectrum of the hydrogen atom. e- Absorbs energy Releases energy

Atomic and mass numbers This should be strictly review... I shouldn’t need to have a long and detailed slide for this, right? NOTE: sometimes mass number, A, is also referred to as the nucleon number

Isotopes Isotopes: change in number of neutrons PROTONS DO NOT CHANGE!!! Ex: Carbon-12 and Carbon-14 Chemical properties of isotopes are the same Physical properties can change among isotopes of an atom - boiling and melting points are higher for isotopes of heavier mass as they move more slowly (think King Bowser on Mario Kart) Some isotopes can have radioactive properties: Ex: Hydrogen, Deuterium, Tritium Draw the atomic symbols for each one. List the number of protons and neutrons for each one.

ions Ions: Change in the number of electrons results in a charged particle Cations: positively charged ions (loses electrons) Anions: negatively charges ions (gains electrons) PROTONS DO NOT CHANGE!!!

Mass spectrometer Used to measure the mass of individual atoms Hydrogen mass = 1.67 x 10-24 g & Carbon mass = 1.99 x 10-23 g And all other masses are in the ranges of 10-24 – 10-22 - what does this mean to you?...... Nothing probably! So, using Carbon-12 as a standard - Carbon is given the relative mass of 12

Mass spectra These are the images/graphs that come off the analysis of the MS Mass to charge ratio m/z compared to the relative intensity Calculating relative atomic mass: - total mass of atoms = (%*m/z) + (%*m/z) + etc. - total mass/number of atoms = relative average mass 0.0309 0.0479