Do Now At a temperature of 255 K, the gas in a cylinder has a volume of 3.0 liters. If the volume of the gas is decreased to 1.5 liters, what must the temperature be for the gas pressure to remain constant? A. 137 K C. 378 K B. 128 K D. 556 K

Do Now At a temperature of 255 K, the gas in a cylinder has a volume of 3.0 liters. If the volume of the gas is decreased to 1.5 liters, what must the temperature be for the gas pressure to remain constant? A. 137 K C. 378 K B. 128 K D. 556 K 3.0 L 1.5 L = 255 K T2

Atomic Structure Chapter 4

Objectives List the main points of Dalton’s atomic theory and describe his evidence for the existence of atoms. Explain how Thomson and Rutherford used data from experiments to produce their atomic models.

Dalton’s Atomic Theory All elements are composed of atoms. All atoms of the same element have the same mass, and atoms of different elements have different masses. Compounds contain atoms of more than one element. In a particular compound, atoms of different elements always combine in the same way.

Rutherford’s Model (1911)

Rutherford’s Discovery All of an atom’s positive charge is concentrated in its nucleus.

Nucleus The dense, positively charged mass located in the center of an atom.

Do Now Which of the following is NOT part of John Dalton’s atomic theory? A. All elements are composed of atoms. B. All atoms of the same element have the same mass. C. Atoms contain subatomic particles. D. A compound contains atoms of more than one element.

Do Now Which of the following is NOT part of John Dalton’s atomic theory? A. All elements are composed of atoms. B. All atoms of the same element have the same mass. C. Atoms contain subatomic particles. D. A compound contains atoms of more than one element.

Summarizing a. Dalton b. Indivisible, solid sphere c. Thomson d. Negative charges evenly scattered through a positively charged mass of matter (plum pudding model) e. Deflection of alpha particles passing through gold foil

The Structure of an Atom Section 4.2

Objectives Identify three subatomic particles and compare their properties. Distinguish the atomic number of an element from the mass number of an isotope, and use these numbers to describe the structure of atoms.

Proton A positively charged subatomic particle that is found in the nucleus of an atom.

Electron A negatively charged subatomic particle that is found in the space outside the nucleus of an atom.

Neutron A neutral subatomic particle that is found in the nucleus of an atom.

Note Protons, electrons, and neutrons can be distinguished by mass, charge, and location in an atom.

Do Now Which statement about subatomic particles is true? A. Protons, neutrons, and electrons all have about the same mass. B. Unlike protons or neutrons, electrons have no mass. C. Neutrons have no charge and no mass. D. An electron has far less mass than either a proton or neutron.

Do Now Which statement about subatomic particles is true? A. Protons, neutrons, and electrons all have about the same mass. B. Unlike protons or neutrons, electrons have no mass. C. Neutrons have no charge and no mass. D. An electron has far less mass than either a proton or neutron.

Objective Distinguish the atomic number of an element from the mass number of an isotope, and use these numbers to describe the structure of atoms.

Atomic Number A unique number for each element that equals the number of protons in an atom of that element. Note: Atoms of different elements have different numbers of protons!!!

Atomic Number Sodium 22.990 Na 11

Mass Number The sum of the number of protons and neutrons in the nucleus of an atom.

Mass Number Number of neutrons Mass number Atomic number = -

Do Now Who provided evidence for the existence of a nucleus in an atom? A. John Dalton C. Democritus B. J.J. Thomson D. Ernest Rutherford

Do Now Who provided evidence for the existence of a nucleus in an atom? A. John Dalton C. Democritus B. J.J. Thomson D. Ernest Rutherford

Isotopes Examples: Oxygen – 16 Oxygen – 17 Oxygen – 18 Atoms of a given element that have different numbers of neutrons and different mass numbers. Examples: Oxygen – 16 Oxygen – 17 Oxygen – 18

Note About Isotopes Isotopes of an element have the same atomic number but different mass numbers because they have different numbers of neutrons.

Do Now In an atomic model, the nucleus contains a positive charge that is: Concentrated in the center of an atom. Spread evenly throughout an atom. Concentrated at multiple sites in an atom. D. Located in the space outside the nucleus.

Do Now In an atomic model, the nucleus contains a positive charge that is: Concentrated in the center of an atom. Spread evenly throughout an atom. Concentrated at multiple sites in an atom. D. Located in the space outside the nucleus.

Do Now In Niels Bohr’s model of the atom (electrons are located in energy levels), electrons move: A. like a ball rolling down a hill. B. like planets orbiting the sun. C. like popcorn in a popcorn popper. D. like beach balls on water waves.

Do Now In Niels Bohr’s model of the atom (electrons are located in energy levels), electrons move: like a ball rolling down a hill. B. like planets orbiting the sun. C. like popcorn in a popcorn popper. D. like beach balls on water waves.

Objectives Describe Bohr’s model of the atom and the evidence for energy levels. Explain how the electron cloud model represents the behavior and locations of electrons in atoms. Distinguish the ground state from excited states of an atom based on electron configurations.

Modern Atomic Theory Section 4.3

Energy Levels The possible energies that electrons in an atom can have.

Electron Cloud A visual model of the most likely locations for the electrons in an atom.

Orbital A region of space around the nucleus where an electron is likely to be found.

Electron Configuration The arrangement of electrons in the orbitals of an atom.

Ground State A state in which all the electrons in an atom have the lowest possible energies.

Do Now The glowing of a neon light is caused by electrons emitting energy as they: Move from lower to higher energy levels. B. Collide with other electrons. C. Move from higher to lower energy D. Collide with the nucleus.

Do Now The glowing of a neon light is caused by electrons emitting energy as they: Move from lower to higher energy levels. B. Collide with other electrons. C. Move from higher to lower energy D. Collide with the nucleus.

Objective Distinguish the ground state from excited states of an atom based on electron configurations.

Do Now What is the difference between an atom in the ground state and an atom in an excited state? The atom in the ground state has less energy and is less stable than the atom in an excited state. The atom in an excited state has one fewer electron that the atom in the ground state. The atom in an excited state has more energy and is less stable than the atom in the ground state. The atom in an excited state has one more electron that the atom in the ground state.

Do Now What is the difference between an atom in the ground state and an atom in an excited state? The atom in the ground state has less energy and is less stable than the atom in an excited state. The atom in an excited state has one fewer electron that the atom in the ground state. The atom in an excited state has more energy and is less stable than the atom in the ground state. The atom in an excited state has one more electron that the atom in the ground state.