Chapter 3 Test Review Study Guide

Inference: As a result of Rutherford’s gold foil experiment, scientists inferred that an atom’s positive charge must be concentrated in the nucleus of the atom.

Creation: Mendeleev created the first periodic table by arranging elements in order of increasing atomic mass.
Patterns: Mendeleev discovered that periodic patterns appeared when he arranged the elements in order of increasing atomic mass.
Modern Organization: The modern periodic table is organized according to atomic number.

Atomic Number: The atomic number of an element is the number of protons in its nucleus.
- The atomic number is the property of an element that indicates the number of protons in its atoms.
Electrons: Electrons orbit the nucleus of an atom and are negatively charged particles.
Neutral Atoms: In an atom, the number of protons and electrons are equal, making atoms neutral.
Mass of Electrons: The mass of an electron is so small that it doesn’t really change the mass of an atom.
Isotopes: Atoms with the same number of protons and different numbers of neutrons are called isotopes.

Element Location: You can predict an element’s characteristic properties based on its location on the periodic table.
Metals: Most elements on the periodic table are classified as metals.
- Metals are malleable, ductile, and can carry an electric current.
- The most reactive metals are found in group one (alkali metals).
- Transition metals tend to be less reactive than the families to the left and right of them.
- Most metals are in the solid state or phase at room temperature.
Nonmetals: Nonmetals can be found on the right side of the periodic table.
- At room temperature, more than half of the nonmetal elements are gases.
- Elements known as nonmetals are located to the right of the metalloids on the periodic table.
Metalloids: Metalloids have properties of both metals and nonmetals.
- At room temperature, all the metalloids are solids, while many of the nonmetals are gases.

Beta Radiation: Beta radiation consists of particles that are identical to electrons.
Radioactivity: The spontaneous emission of radiation by an unstable atomic nucleus was named radioactivity by Marie Curie.
Radioactive Decay: The atomic nuclei of unstable isotopes release fast-moving particles and energy in a process called radioactive decay.
Half-Life: The half-life of a radioactive isotope is the length of time needed for half of the atoms of a sample to decay.
- Because radioactive isotopes decay at a predictable rate, the half-life can be used to tell how old a material is by the process of radioactive dating.
Radioactive Isotopes: Radioactive isotopes called tracers can be used to detect some medical problems.

Alpha Particle: A piece of paper will provide protection from alpha radiation. An alpha particle is released when radium decays into radon.
Beta Particle: A beta particle is released when changing a neutron into a proton when lead decays into bismuth.
Gamma Radiation: Gamma radiation is always released during any type of radioactive decay.
- When uranium-238 decays into lead-206, the difference between the mass of uranium and lead is 32 amu, while the difference between their atomic numbers is 10.

Conductivity: Elements that easily transmit electricity and heat display the property known as conductivity.
Reactivity of Metals: The chemical reactivity of metals tends to decrease from left to right across the periodic table.
Unique Position of Hydrogen: Hydrogen is so unique that it could easily be placed in either group 1 or group 17.

Columns & Groups: A column of elements on the periodic table is called a group or a family because they have similar characteristic properties.
- The elements in the same column (or group or family) on the periodic table have similar characteristic properties.
Horizontal Rows: The horizontal rows on the periodic table are known as series or periods.
- Electrons in the same row on the periodic table have periodic properties that change in a pattern.

Alkaline Earth Metals: The two most common alkaline earth metals are calcium and magnesium.
Halogen Family: Fluorine, chlorine, bromine, and iodine are all part of the Halogen family.
Noble Gases: Elements that do not react to form compounds under normal conditions are the Noble Gases.
Specific Element Properties: The element in group 18, period 4 is krypton and it would be a gas at room temperature and would not react with other elements.