Unit 7 science exam study guide

anything that has mass and takes up space

the simplest pure substances, and they cannot be broken down into any other substances

pure substance made of two or more elements that are combined chemically in a specific ratio

two or more substances—elements, compounds, or both—that are in the same place but are not chemically combined

the smallest particle of an element

scientific theory
a well-tested idea that explains and connects a wide range of observations

physical, mental, visual, and other representations of an idea to help people understand what they cannot observe directly

Negatively charged particles that move around outside the nucleus of an atom

The central core of the atom, containing protons and usually neutrons

Small, positively charged particles that are found in the nucleus of an atom

energy level
A region around the nucleus in which electrons of the same energy are likely to be found

Small, uncharged particles that are found in the nucleus of an atom

valence electrons
The electrons that are in the highest energy level of an atom and that are involved in chemical reactions

electron dot diagram
A representation of the valence electrons in an atom, using dots

chemical bond
the force of attraction that holds two atoms together as a result of the rearrangement of electrons between them

A one- or two-letter set of characters that is used to identify an element

atomic number
the number of protons in the nucleus of an atom

A row of elements across the periodic table

Elements in the same column

another name for a group

noble gases
The elements in Group 18

The elements in Group 17

alkali metal
An element belonging to Group 1 of the periodic table

an atom or group of atoms that has an electric charge

polyatomic ions
Ions that are made of more than one atom

ionic bond
the attraction between two oppositely charged ions

ionic compound
A compound that consists of positive and negative ions

chemical formula
a combination of symbols that shows the ratio of elements in a compound

tells you the ratio of elements in the compound

An orderly, three-dimensional pattern of ions or atoms in a solid

covalent bond
The chemical bond formed when two atoms share electrons

a neutral group of atoms joined by covalent bonds

double bond
A chemical bond formed when atoms share two pairs of electrons

triple bond
A chemical bond formed when atoms share three pairs of electrons

molecular compound
a compound that is composed of molecules

polar bond
A covalent bond in which electrons are shared unequally

nonpolar bond
A covalent bond in which electrons are shared equally

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