CEM 141 CHAPTER 1 LEARNING OBJECTIVES QUESTIONS WITH A GUARANTEED A+

Stable systems form when? - The attractive forces and the repulsive forces are equal. Claim, evidence and reasoning for the existence of negatively charged particles in an atom. - Claim: Electron's are negatively charged particles of an atom. Evidence: JJ's cathode ray. Electron's were ejected from the cathode, regardless of what the cathode was made of. Reasoning: Electrons must be negatively charged because they accelerate towards the anode. Claim, evidence and reasoning for the existence of a small, positively charged nucleus in the atom. - Claim: A small, massive, positively charged nucleus exists in the atom. Evidence: Rutherford's gold foil experiment. The majority of the alpha particles went through the gold foil. Some being deflected. Reasoning: Most of the atom is empty space except the small, positive nucleus in the middle deflecting some of the alpha particles. Dalton's Atom - Thomson's plum pudding atom - Composed purely of negatively charged electrons in a positively charged blob. Rutherford's atom - The existence of a positive nucleus. Niel Bohr's atom - Electrons were in shells that orbited the nucleus. The depth of the PE well can tell you.. - How much energy would be needed to overcome the interaction.Similarities between gravitational and electrostatic force - -Field force -Both attractive -Require two or more objects -Force decreases as distance increases. Why are neutrons harder to detect? - Neutral in charge- not manipulated with electric and magnetic fields. LDF's are _____________ atoms. Covalent bonds are ___________ atoms. - Between, within Definition of everyday theory - linking facts to one another but still had doubt and speculation. Definition of scientific theory - A set of rules explaining observed phenomenon, rooted in "experienced" facts. The position of the PE well (X axis) can tell you..... - How far away the atom centers are when they are most stable. What is happening at the potential well in an energy diagram? - At the potential well, the forces are most stable. The two atoms have so much energy so they cannot stay in the well. To have them stay in the well, we need to transfer energy by collision. Electrostatic force characteristics - -Attractive and repulsive force -Increase as the charge of the objects increase. -Stronger than gravitational force. -Electrostatic attraction between charged particles. Construct an atomic level explanation for why two isolated atoms would attract each other as they approach, and they would repel if they get too close to each other. - In an isolated system, the total energy is constant. The two atoms attract each other because of LDF's. In a moment, there is anuneven distribution of electrons. This induces an an instantaneous dipole where there is a partial negative and positive attracting each other. During this stage, kinetic energy increases where potential energy is decreasing. As the atoms get very close, they are essentially overlapping. The electrostatic repulsion between the electrons are forcing them apart. This is when potential energy will increase and kinetic energy will decrease. Explain the changes in potential energy, the kinetic energy and the total energy as two isolated helium atoms approach each other. - In an isolated system, the total energy is constant. As the two He atoms approach each other, kinetic energy will increase because of the electrostatic attraction. As kinetic energy increases, potential energy decreases because the total system is constant