Science ch 4

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41 terms

ion

an atom or a group of atoms that has an electric charge

When a neutral atom loses a valence electron, it loses a negative charge. It becomes a positive ion. When a neutral atom gains an electron it gains a negative charge. It becomes a negative ion.

How do ions form?

poly

many

polyatomic ions

ions that are made up of more than 1 atom

ionic bond

the attraction between two oppositely charged ions

ionic compound

a compound that consists of positive and negative ions

KI

Write the symbols for the ions that form when potassium and iodine react to form the ionic compound potassium iodide

Because potassium is 1+ and iodine is 1- making it electrically neutral

Why is potassium iodide electrically neutral?

chemical formula

a group of symbols that shows the ratio of elements in a compound

subscripts

numbers written below the line that tell how many atoms of a given type are in a compound.

superscripts

Used in footnotes or reference purposes.

To write a formula for an ionic compound, write the symbol of the positive ion and then the symbol of the negative ion. Add the subscripts that are needed to balance the charges. For an ionic compound, the name of the positive ion comes first, followed by the name of the negative ion.

How are the formulas and names of ionic compounds written?

That there are 2 sodium atoms for every sulfur atom.

Explain what the formula Na2S means.

crystal

ions formed in an orderly, three-dimensional arrangement

covalent bond

a bond formed when atoms share one or more pairs of electrons

molecule

two or more atoms held together by covalent bonds

The attractions between the shared electrons and the protons in the nucleus of each atom hold the atoms together in a covalent bond

How are atoms held together in a covalent bond?

double bond

a bond in which two atoms share two pairs of electrons

molecular compound

a compound that is composed of molecules

triple bond

a bond formed by sharing three pairs of electrons

valence electrons

electrons on the outermost energy level of an atom

electron dot diagram

a model of an atom in which each dot represents a valence electron

chemical bond

the force that holds two atoms together

octet rule

States that atoms lose, gain or share electrons in order to acquire a full set of eight valence electrons

electronegativity

a measure of the ability of an atom in a chemical compound to attract electrons

metallic bond

a bond formed by the attraction between positively charged metal ions and the electrons around them

alloy

a mixture of two or more metals

Ionic bonds typically form between charged atoms of metals and nonmetals. Covalent bonds usually form between uncharged atoms of nonmetals.

What is the difference between ionic bonds and covalent bonds?

solvent

substance in which a solute is dissolved to form a solution

solute

the substance that is dissolved

dissociate

to separate; to break association with

electrolysis

The process of decomposing a chemical compound by the passage of an electric current.

electronegativity trend

decreases from top to bottom in a group; increases from left to right in a period

malleability

the ability of a substance to be hammered or beaten into thin sheets

ductility

the ability of a substance to be drawn, pulled, or extruded through a small opening to produce a wire

luster

the way a mineral reflects light

conductivity

the ability of a material to allow either heat or electricity to flow through it

reactivity

the ability of a substance to combine chemically with another substance

insulator

a material that does not allow heat or electrons to move through it easily

semiconductor

an element that can conduct electricity under some conditions

A metal crystal is composed of closely packed, positively charged metal ions. The valence electrons drift among the ions

What is the structure of a metal crystal?

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