Basic ChemistryBiol 101

Outline

• Describe the basic structure of an atom• Recognize the importance of electrons • Understand isotopes and radioactivity• Describe chemical bonds and why they form• Be aware of the properties of water• Understand pH and buffers

Matter, Molecules Elements & Atoms

Matter

Compounds … Molecules

Elements … Atoms

Chemical Composition of the Human Body

Structure of an Atom - Subatomic Particles

Mass Number

+

+

– –

+

–

2

2

2

Protons

Neutrons

Electrons

Massnumber = 4

+

+

2e–

Electroncloud

NucleusHelium atom

Mass Number

+

–

6

6

6

Protons

Neutrons

Electrons

Massnumber = 12

+ +

6e–

Nucleus

Electroncloud

Carbon atom

Atomic Number and Atomic Weight or Mass Number

Periodic Table of the Elements

Isotopes

Chart of Isotopes

Radioactivity

• Beta – neutron decay to loss of electron• Alpha – loss of two neutrons and two protons• Gamma – loss of energy

Energy from different sources

Source Energy (MJ/kg)

Firewood 16

Coal 9-30

Natural Gas 39

Crude oil 45

Uranium (nuclear fission) 500,000

Radioactive Dating

Radioisotope half life

C-14 5730 years

H-3 12.25 years

U-238 4.5 billion years

Summary of Isotopes

• 92 naturally occurring elements• 270 stable isotopes• 50 natural radioisotopes• 1000’s artificial isotopes• Radioactivity is released by unstable isotopes• Radioactivity

– Always comes from the breakdown of a nucleus– Lot of energy– Uses: Energy, Dating Materials, Research & Medicine

Energy Levels (Electron Shells)

Hydrogen (H)Atomic number = 1

Carbon (C)Atomic number = 6

Nitrogen (N)Atomic number = 7

Oxygen (O)Atomic number = 8

Outermost electron shell holds 8 electrons

First electron shell holds 2 electrons

Electron

Nucleus

Energy Levels (Electron Shells) & Electron Arrangements

Energy Levels (Electron Shells)

Ionic Bond Formation

Sodium Chlorine Sodium Chloride

Molecules Have Emergent Properties

Covalent Bonding

Covalent Bonds

Molecular and

Structural

Formulas

Water Structure and Hydrogen Bonding

Water Structure and Hydrogen Bonding

Hydrogen bond(+)

(+)

H

H(+)

(+)

(–)

(–)

(–)(–)

O

Fig. 2.15(TE Art) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Properties of Water

Cohesion Adhesion

Properties of Water

High Surface Tension

Properties of Water

Moderates Temperature

High Heat Storage

High Heat of Vaporization

Fig. 2.11b

Properties of Water

Ice Formation

WatermoleculesSalt

crystal

Na+

Cl–

Cl–

Na+

Na+

Na+

Cl–

Cl–

Fig. 2.17(TE Art) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Properties of Water

Solvent forms

Hydration Shells

Properties of Water

H2O

H+ + OH-

pH = hydrogen ion concentration

Basic solutionOven cleaner

Acidic solution

Neutral solution

pH scale0

1

2

3

4

5

6

7

8

9

10

11

12

Lemon juice, gastric juice

Grapefruit juice, soft drink

Tomato juice

Human urine

Pure waterHuman blood

Seawater

Milk of magnesia

Household ammonia

Household bleachIn

crea

sing

ly A

CID

IC(H

ighe

r co

ncen

trat

ion

of H

+)

NEUTRAL[H+]=[OH–]

H+ H+

H+ OH– H+

H+ H+

OH– H+ H+

OH–

OH–

H+ H+OH–

OH– OH–

H+ H+H+

OH–

OH–

OH– OH–

OH–OH– H+ Incr

easi

ngly

BA

SIC

(Low

er c

once

ntra

tion

of H

+)

OH–

H+

14

13

Buffers

END Basic Chemistry