Chapter 16, 17 Science Vocab.

Radioactive Element

A radioactive element is one in which the nucleus breaks down and gives off particles and energy.

Allotrope

Allotropes are different molecular structures of the same element.

Atom

An atom is the smallest particle of an element that retains the element's properties.

Electron Cloud

An electron cloud is the area around the nucleus of an atom where electrons are most likely to be found.

Electron Dot Diagram

An electron dot diagram uses the chemical symbol of an element surrounded by dots to represent the number of electrons in the outermost energy level.

Isotope

Atoms of the same element that have different numbers of neutrons are called isotopes.

Electron

Electrons are particles with an electric charge of 1-.

Transuranium Element

Elements that have more than 92 protons, the atomic number of uranium, are called transuranium elements shows a small sample of the transuranium element americium.

Metallic Bonding

In metallic bonding, positively charged metallic ions are surrounded by a sea of electrons

Periodic Table

In the modern periodic table, the elements are arranged by increasing atomic number-not atomic mass-and by periodic changes in physical and chemical properties.

Metalloid

Metalloids are elements that have some properties of metals and some properties of nonmetals.

Ductile

Metals are also ductile, which means they can be drawn into wires.

Metal

Metals are elements that are shiny, malleable, ductile, and good conductors of heat and electricity.

Malleable

Metals are malleable (MA lee uh bul), which means they can be hammered or rolled into sheets.

Neutron

Neutrons are electrically neutral particles in the nucleus; they do not have a charge.

Proton

Protons are particles in the nucleus with an electric charge of 1+.

Quark

Scientists have inferred that protons and neutrons are composed of smaller particles called quarks.

Semiconductor

Semiconductors are elements that conduct an electric current under certain conditions.

Average Atomic Mass

The average atomic mass of an element is the weighted average mass of all naturally occurring isotopes of an element, measured in atomic mass units (amu), according to their natural abundances.

Period

The horizontal rows of elements in the periodic table are called periods and are numbered 1 through 7.

Mass Number

The mass number of an atom is the sum of the number of protons and the number of neutrons in the nucleus of an atom.

Atomic Number

The number of protons in an atom's nucleus is equal to its atomic number.

Nucleus

The small, positively charged center of the atom is called the nucleus.

Group

The vertical columns in the periodic table are called groups (also called families), and they are numbered 1 through 18.

Transition Element

Transition elements are the elements in groups 3 through 12 in the periodic table.