Chem Quiz 2

Lewis Structures

-A diagram used to show the arrangement of atoms and valence electrons in a molecule. -Includes both bonding electron pairs and lone pairs (non-bonding electron pairs)

Chemical Bond

-An attraction between two or more atoms -Due to interaction between valence electrons

Octet Rule

-An octet in the outer (valence) shell makes atoms stable -Octet = 8 electrons -Electrons are lost, gained or shared to form an octet

Functional Groups

-Composed of an atom or group of atoms -Provide a way to classify organic compounds -Part of an organic molecule where chemical reactions take place

Naming Binary Covalent Compounds:

-Name each element -End the last element in -ide -Add prefixes to show the number of atoms **The first element doesn't get the mono prefix Prefixes mono:1 di: 2 tri: 3 tetra:4 penta:5 hexa: 6

Writing an Ionic Formula

1. Balance the charges. 2. Write the cation first then the anion. 3. Write the number of ions needed as subscripts. Don't write the charges of the ions in the completed formula.

Polyatomic Ions

A group of atoms bonded together with an overall charge. (NH4+, ammonium)

Electronegativity

A measure of how strongly an atom attracts electrons

Ion

An atom or group of atoms that has a charge. Cation - positively charged ion Anion - negatively charged ion Ionic compound - a cation bonded to an anion (metal bonded to a non-metal)

Shape of a water molecule?

Bent

Covalent Compounds

Compounds that are made of covalent bonds (mixture of non-metals) Example: Water (H2O)

Binary Ionic Compounds

Contain 2 different elements - a cation and an anion

Ternary Compounds

Contain at least 3 elements Al(HCO3)3 Aluminum bicarbonate *If the subscript is 2 or more, write the polyatomic ion in parentheses in the formula.

Ionic compund

Contains a cation bonded to an anion

Which element cannot be the center atom of a Lewis structure?

H

Elements that Are Always Found as Covalent Compounds

H₂, N₂, O₂, F₂, Cl₂, Br₂, I₂, P₄, S₈

pure (nonpolar) covalent bond:

If the atoms that form a covalent bond are identical bonding electrons are shared equally. Ex: Cl2, H2

Ionic Bonds

Ionic Bonds (make Ionic Compounds): One atom gives up one electron to the other atom. A cation and an anion forms. The electrostatic force of attraction brings these two ions together and an ionic bond forms. It's a bond between a metal and a non-metal.

Formulas of Ionic Compounds

Ionic compounds - must be neutral (no overall charge) - have the simplest formula that balances the charges

Variable Cations

Metals except groups 1,2,Al,Zn,Cd,Ag usually form several different ions each with a different charge.

Cations

Metals lose their valence electrons and form cations Often, the cations formed have a Group 1 metals → ion + Group 2 metals → ion 2+ Group 13 metals→ ion 3+

Ions from Non-metals

Non-metals gain valence electrons and form anions The anions formed often have a completed shell Group 17 non-metals ⎯→ ion - Group 16 non-metals ⎯→ ion 2- Group 15 non-metals ⎯→ ion 3-

Naming Ternary Compounds

Same rules as naming binary compounds (cation then anion), but use the name(s) of the polyatomic ion(s) where appropriate.

Electron Dot Structures

Symbols of atoms with dots to represent the valence-shell electrons

Covalent Bonds

Two atoms, sharing electrons and making a bond They make Molecular (covalent) Compounds. It's a bond between two non-metals.

Binary Covalent Compounds

Two bonded non-metals Example: CO, NH3

VSEPR

Valence Shell Electron Pair Repulsion molecules assume a geometry that minimizes repulsions between electron pairs

polar covalent bond:

When the atoms linked by a covalent bond are different, the bonding electrons are shared, but no longer equally.

Names of Variable Cations

Write the charge of the cation in Roman numerals and in parentheses after the name of the metal

Made up of four shared electrons and shown as two lines between atoms in a Lewis structure

double bond

Made up of two unshared electrons and shown as two dots in a Lewis structure:

lone pair

made up of two shared electrons and shown as a line between atoms in a Lewis structure

single bond

In a polar covalent bond, electrons are shifted toward

the more electronegative atom; thus, the more electronegative atom is the one with the partial negative charge

Made up of six shared electrons shown as three lines between atoms in a Lewis structure

triple bond