CHAPTER 4 Study Guide

4.1 Studying Atoms

Key Concepts

• Dalton proposed the theory that all matter is made up of individual particles called atoms, which cannot be divided.

• Thomson's experiments provided the first evidence that atoms are made of even smaller particles.

• According to Rutherford's model, all of an atom's positive charge is concentrated in its nucleus.

Vocabulary

nucleus, p. 105

4.2 The Structure of an Atom

Key Concepts

• Protons, electrons. and neutrons are subatomic particles.

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

• Atoms of different elements have different numbers of protons.

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

Vocabulary

proton, p. 108

electron, p. 108

neutron, p. 109

atomic number, p. 110

mass number, p. 110

isotopes, p. 112

4.3 Modern Atomic Theory

Key Concepts

• An electron in an atom can move from one energy level to another when the atom gains or loses energy.

• Scientists use the electron cloud model to describe the possible locations of electrons around the nucleus.

• An electron cloud is a good approximation of how electrons behave in their orbitals.

• The most stable electron configuration is the one in which the electrons are in orbitals with the lowest possible energies.

Vocabulary

energy levels, p. 114

electron cloud, p. 116

orbital, p. 117

electron configuration, p. 118

ground state, p. 118

Thinking Visually

Table of Properties Use information from the chapter to complete the table below.

Table of Contents