CHEM 217 Lecture Notes - Lecture 3: Phenyl Group, Organic Chemistry, Alkene

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Unit 3

3. 1

Compound properties generally very different from the properties of the elements

Law of definite proportions applies to compounds not mixtures

3. 2 BO N D S

Result of interactions between charged particles

Ionic bonds

oMetal lose (e-) to nonmetals

oElectrostatic forces make oppositely charged ions attracted to each other

oAs multiple ions pairs form, they can group together and th result is an ionic compound in the

solid phase composed of a lattice

Covalent bonds

oNonmetal & nonmetal

oNo transfer of electrons. Insteadm they share them

oShared electrons interact with both nuclei which loewers potential anergy of one system through

electrostatic interactions

oMolecular compound, composed of individually bound covalent molecules

oUnderstand stability of a covalent bond by considering the most stable/lowest potential energy

configuration of a negative charge interacting with two positive charges

oShowed that electrons hold the bonding atoms toether by attracting positively harged nuclei of

both

3. 3 R E P R E S EN T I NG CO M P O U N D S

Easiest way: chemical formula : indicates elements present in the compounds and the relative numbering

of atoms or ions of each

oUsually list the more metallic (or more positively charged ) elements first followed by less

metallic (or more negatively charged ones)

Types of formulas

oEmpirical formula

Gives relative # of atoms of each element in a compound

oMolecular formula

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Gives actual # of atoms of each element in a compound

Ex. hydrogen peroxide

oEmpirial – HO

oMolecular H2O2

Molecular always a whole-number multiple of the empirical and for some compounds they are the same

A structural formula uses lines to represent covalent bonds and shows how atoms in a molecule are

connected

oAlso may be written to give asense of geometry

oStrucural can also depict types of bonds

Structural formula conveys the most information while empricial conveys the least

Elements can be atomic or molecular// compounds can be molecular, ionic

oAtomic elements – exist in nature with single atom basic units, most elements

oMolecular elements – exist as molecules – two or more atoms of the element bound together

oMolecular compounds are two or more covalently bound nonmetals. Basic units are molecules

composed of constituent atoms

oIonic compounds – made of cations (usualy one type of metal) and anions (1 or more nonmetals)

bound ionically

Basic unit is formula unit, the smallest, electrically neutral collection of ions and do not

exist as discrete entities but as a part of a large lattice

Many common ionic compounds contain ions that are composed of a group of

covalently bound atoms with an overall charge

3. 4 FO R MU L A & NA M ES

Common names – no info conveyed about composition

Systematic names – more info

Ionic compounds – occur through earth’s crust as minerals. Generally stable because of cation/anion

interactions

Writing formulas for ionic compounds

oSince they’re charge-neutral and since many elements ofrm only one type of ion with a

predictable charge, the formulas for many ionic compounds can be deduced from their

constituent elements

oSummary

Always contain positive and negative ions

Sum of the charges must be equal to the sum of the negative ions and of the positive

ions

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A formula reflects the smallest whole number ratio of ions

Procedure for writing ionic compounds

o1. Write the symbol for the metal cation and its charge, followed by the symbol for the non-

metal anion and its charge. Obtain charges from the elements group # in table

o2. Adjust subscript on each cation and anion to balance overall charge

o3. Check that the sum of the charges of the cations equals the sum of the charges of the anions

Naming ionic compounds

oFor metals that form cations with one possible charge, the name is just the metal

oFor metals that form cations with more than 1 possible charge, the name is metal followed by

the charge in roman numerals in brackets, this Fe2+ is Iron (II), etc.

oNames for nonatomic anions consist of base name of the element followed by suffix-ide

oIonic compounds with a polyatomic ion are named the same way but with the name of the

polyatomic ion

oIf the compound contains both a polyatomic cation and polyatomic anion, noth are named

Ex. NH4NO3

Most polyatomic ions are oxyanions – anions containing oxygen and another element

oWhen oxyanions contain different numbers of oxygen atoms, they are named systematically

according to # of O in the ion.

If there are only two ions in the series, the one with more oxygen atoms has ending –

ate and the one with fewer has ending –ite.

Ex. NO3 - Nitrate

Ex. NO2 – Nitrite

If there are more than 2 ions in the series, the prefixes hypo- meaning less than and per-

meaning more than are used.

EX. ClO- is hypochlorite (less oxygenthan chlorite) and ClO4- is perchlorate (more

oxygen than chlorate)

Hydrated ionic compounds

oSome ionic compounds called hydrates have a specific # of water molecules associated with each

formula unit

oThe H2O molecules are waters of hydration – they can usually be removed by heating the

compound

oHydrates are named just as other ionic compounds but they are given additional name “prefix

hydrate” where the prefix indicates the # of water molecules associated with each formula unit

Written as:

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Document Summary

Compound properties generally very different from the properties of the elements. Law of definite proportions applies to compounds not mixtures. Ionic bonds: metal lose (e-) to nonmetals o o. Electrostatic forces make oppositely charged ions attracted to each other. As multiple ions pairs form, they can group together and th result is an ionic compound in the solid phase composed of a lattice. Covalent bonds: nonmetal & nonmetal, no transfer of electrons. Showed that electrons hold the bonding atoms toether by attracting positively harged nuclei of both. 3 r e p r e s e n t i n g c o m p o u n d s. Gives relative # of atoms of each element in a compound: molecular formula. Gives actual # of atoms of each element in a compound. Molecular always a whole-number multiple of the empirical and for some compounds they are the same.

Related Questions

Chemistry 162 Lab Activity

Introduction Water has an amazing ability to adhere (stick) toitself and to other substances. Hydrogen bonds form when hydrogenatoms covalently bonded to nitrogen (N), oxygen (O), or fluorine(F) in the form of covalent compounds such as ammonia (NH3), water(H2O) and hydrogen fluoride gas (HF). In these molecules, thehydrogen atoms do not pull as strongly on the shared electrons asthe N, O, or F atoms. Therefore, the molecules are polar; thehydrogen atoms become positively charged and are able to formhydrogen bonds to negative ions or negatively charged parts ofother molecules (such as the N, O, and F atoms that becomenegatively charged in these compounds). Hydrogen bonds are not truebonds like covalent bonds or ionic bonds. Hydrogen bonds areattractions of electrostatic force caused by the difference incharge between slightly positive hydrogen ions and other, slightlynegative ions. These attractions are much weaker than true ionic orcovalent bonds, but they are strong enough to result in someinteresting properties.

In the case of water, hydrogen bonds form between neighboringhydrogen and oxygen atoms of adjacent water molecules. Theattraction between individual water molecules creates a bond knownas a hydrogen bond (Fig. 1).
Fig. 1: Hydrogen bonds shown as the dotted lines between watermolecules.
Cohesion Molecules of pure substances are attracted to themselves.This sticking together of like substances is called cohesion.Depending on how attracted molecules of the same substance are toone another, the substance will be more or less cohesive. Hydrogenbonds cause water to be exceptionally attracted to each other.Therefore, water is very cohesive.
Adhesion Adhesion is similar to cohesion, but it involves unlike(i.e. different) substances sticking together. Water is veryadhesive; it sticks well to a variety of different substances.Water sticks to other things for the same reason it sticks toitself â because it is polar so it is attracted to substances thathave charges. In this lab activity, you will be asked to use thematerials and procedures provided to explore the properties ofwater that involve both cohesion and adhesion. Be sure to writedown your observations and results as you progress. sults as youprogress.

Fig. 1

Hydrogen bonds shown as the dotted

lines between water molecules.

Part 1:

Exploring Water

Procedure

How many drops of water can you fit on the surface of a pennywithout the water spilling over?

Predict how many drops of water will fit on a penny. Record yourprediction.

Use the plastic pipette to drop water on the surface of a penny.Drop car

efully and slowly to fit as

many drops as possible on the penny. Count each drop until thewater spills over the side of the

penny and record your results.

Compare your results to those of your classmates. Record therange and calculate the average

number

of drops that fit on a penny.

Add more drops to the penny, without letting the water spillover. Carefully observe and draw the

water on the penny.

Record

a hypothesis for the behavior of water that you observed, usingthe language of cohesion

and adhesion

in relation to the water and the penny.

Record your results and

thinking in your notebook.

Can you

disturb

the water on the penny without spilling it?

dd drops of water to the penny, until the water is almost readyto spill over.

Predict what will

happen when you insert a toothpick into the surface of the waterpiled on the

penny. Record your prediction.

Insert the

toothpick

and carefully observe the surface of the water.

Try inserting the

toothpick

in various ways. Observe the surface of the water.

Pay special attention to

the water surface where the skewer enters the water.

Record your observations and draw what you see.

Repeat

these

procedures using a paper clip and the metal clip part of abinder clip. Try to indent the

pile of water as much as p

ossible without spilling it.

Record your observations and dra

w what you see, paying careful

attention to the surface of the

water.

Record

a hypothesis for the behavior of water that you observed usingthe language of cohesion

and adhesion in relation to the

toothpick

, the paperclip, the binder clip, and the water.

Record your results and

thinking in your notebook.would you please answer the questionfor me . Thanks

CHEM 217 Lecture Notes - Lecture 3: Phenyl Group, Organic Chemistry, Alkene

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