Chapter 4
Section 1
1.
Atom- is the smallest particle of an element.
2.
Electrons- the negatively charged particles.
3.
Nucleus- the central core of the atom.
4.
Protons- Rutherford called the positively charged particles in an atom’s nucleus.
5.
Energy level- the specific amount of energy it has.
6.
Neutron- was hard to detect because it has no electric charge.
7.
Atomic number- the number of protons in the nucleus of an atom.
8.
Isotopes- atoms of the same element that have different numbers of neutrons.
9.
Mass number- which is the sum of the protons and neutrons in the nucleus of an atom.
Section 2
1.
Atomic mass- is the average mass of all the isotopes of an element.
2.
Periodic table- is an arrangement of the elements showing the repeating pattern of their properties.
3.
Periods- a horizontal row of elements in the periodic table.
4.
Groups- a vertical column of the periodic table.
5.
Chemical symbol- is a representation of an element usually consisting of one or two letters.
Section 3
1.
Metals- elements that are good conductors of electric current and heat.
2.
Malleable- is one that can be hammered or rolled into flat sheets or other shapes.
3.
Ductile- is one that can be pulled out, or drawn, into a long wire.
4.
Thermal conductivity- is the ability of an object to transfer heat.

5.
Electrical Conductivity- is the ability of an object to transfer electric current.
6.
Reactivity- the ease and speed with which a substance reacts with other substances.
7.
Corrosion- the gradual wearing away of a metal due to a chemical reaction.
8.
Alkali metals- The metals in Group 1, from lithium to francium.
9.
Alkaline earth metals- an element in Group 2 of the periodic table.
10.
Transition metals- One of the elements in Group 3 through 12 of the periodic table.
11.
Particle Accelerators- move atomic nuclei faster and faster until they have reached very high speeds.
Section 4
1.
Nonmetal- is an element that lacks most of a metal.
2.
Diatomic molecule- is a molecule that consists of two atoms.
3.
Halogens- an element found in the Group 17 of the periodic table.
4.
Inert gases- the elements in Group 18.
5.
Semimetals- have some properties of metals but also have properties of metals but also have properties that are typical of nonmetals.
6.
Semiconductors- substances that can conduct electric current under some conditions but not under other conditions.
Section 5
1.
Radioactive decay- the atomic nuclei of unstable isotopes release fast-moving particles and energy.
2.
Radioactivity- the ability of a substance to spontaneously emit radiation; a property of unstable isotopes.
3.
Alpha particle- consists of two protons and two neutrons and is positively charged.

4.
Beta particle- is a fast-moving electron given off by a nucleus during radioactive decay.
5.
Gamma radiation- consists of high-energy waves, similar to X-rays
6.
Tracers- are radioactive isotopes that can be followed through the steps of a chemical reaction or an industrial process.