Science Unit 4

Valence Electrons

electrons with the highest electric charge

Electron Dot Diagrams (definition & how to draw)

a diagram that shows you how many valence electrons are in an element, to draw, you write the element’s name and then put dots around it to represent to valence electrons

Chemical Bond

force of attraction that holds atoms together

Groups vs Periods on the periodic table

groups are up and down and periods are side to side

General properties & behaviors of core Groups

Metals (esp. Alkali Metals), Nonmetals (esp. Hydrogen, Halogens, & Noble Gases), & Metalloids-

Ion

Definition

an atom or group of atoms that have an electric charge

How ions form

when an atom gains or loses electons

Positive vs Negative Ion

positive ions form when an atom loses electrons, negative ions form when atoms gain electrons

Polyatomic Ions

two or more atoms in an ion

Common Ion Examples from pages 132 & 135 of textbook

MAKE SURE TO KNOW!

Ionic Bond

two oppositely charged atoms chemically bonded together

Ionic Compound

oppositely charged ions

Chemical Formula (including subscript)

a group of symbols that shows the ration of elements in a compound, including subscript

General properties of ionic compounds

hard solids with high melting and high boiling points

Covalent Bond: Definition

a chemical bond formed when two or more atoms share electrons

How They Form

when two nonmetal atoms share valence electron(s)

Single vs Double vs Triple Bond

a single bond is when two atoms share one pair of electrons, a double bond is when two atoms share two pairs of electrons, and a triple bond is when two atoms share three pairs of electrons

Molecular Compound

a chemical substance formed when nonmetal share valence electrons to create neutral molecules

General properties of molecular compounds

good insulators, lower melting and boiling points

Nonpolar vs Polar covalent bonds

Definition

A nonpolar bond is when two atoms of the element share electrons equally, and a polar bond is when two atoms of an element do not share electrons equally

How They Form

based on how atoms share electrons during a covalent bond

Differences in properties

Polar molecules (ex. H 20) require more energy to  

break their bonds than nonpolar molecules (ex. O2), leading to higher melting/boiling points. 

van der Waals forces

The attractions between the slight negative & positive charges in a molecule

Metal Crystal

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

Metallic Bond

An attraction between a positive metal ion and the electrons surrounding it.

General properties of metals

Hard, dense, & shiny. Almost all metals are solid at room temperature. Most metals have strong thermal and electrical conductivity

Explain why metals have these properties, connecting it back to their ions & structure

High Luster

The luster of a metal is due to its valence electrons. When light strikes the electrons, they absorb the light and then re-emit the light.

Thermal Conductivity

Metals conduct heat easily because valence electrons within the metal are free to move. Electrons in the warmer part of the metal can transfer energy to electrons in the cooler parts of the metal.

Electric Conductivity

Metals conduct electric current easily because valence electrons within the metal are free to move.

Alloy

Definition- a mixture made of two or more elements, at least one of which is a metal

Common Uses

Steel, Bronze, Brass