essential chemistry for biology chapter 2 elements and the periodic table atoms and subatomic...

Essential Chemistry for Biology CHAPTER 2 Essential Chemistry for Biology CHAPTER 2

• Elements and the Periodic Table

• Atoms and Subatomic Particles

• Atomic Number, Mass, and Isotopes of Elements

• Chemical Bonding and Molecules

• Chemical Reactions

• Properties of Water

• pH and Acid/Base Balance

He - Helium

Fe - Iron (from ferrum)

C - Carbon

Au - Gold (from aurum)

Al - Aluminum

Cu - copper (from cuprum)

Periodic Table of the Elements

Elements are fundamental categories of matter that cannot be broken down into

other types of matter.

Figure 2.3

The Elements Found in Living Things

Life is made mostly of “CHON”

Every Element (Category) is Composed of Atoms

The element gold (Au)

Atoms Are the Apples in the Bins Called Elements• Atoms (apples) are the individual items belonging to a specific element (variety) in the Periodic Table.

• Atoms belonging to an element are very similar but not identical (they have slightly different masses)

Three atoms (apples) from the variety

(element) Golden Delicious

24.2 g 29.6 g 25.9 g

Periodic Table of Apple Varieties

Atoms Are Composed of Three Types of Particles

Atoms of an Element Always Have a Unique Number of Protons

Boron Carbon Nitrogen Oxygen Fluorine Neon

The number of electrons = number of protons in an electrically balanced atom

Figure 2.7

Different Orbits or Shells Have Different Capacities For Electrons

A Closer Look at the Numbers For Each Element

Numbers That Define Elemental Size and Behavior

• Size and numbers of parts

• Chemical behavior

Elements are organized by:

Heavier elements are to the right

and downwards in rows

Elements with similar behavior are in the same

column

12.011

Electron Arrangement and the Chemical Properties of Atoms

Atoms of elements with the same number of outer shell electrons have similar chemical behavior.

Both nitrogen at bismuth form 3 bonds with neighboring atoms

Isotopes are alternate atomic forms for an element.

24.2 g 29.6 g 25.9 g

Three “isotopes” of Golden Delicious

Mass number is the average mass of the different isotopes found in nature.

Radioactive Isotopes can be used to form images

Positron Emission Tomography (PET) scan looks for where radioactive fluorine-sugar is being used in the brain (blue areas)

Chemical Bonding and Molecules

Three types of chemical bonds

• Ionic bonds

• Covalent bonds

• Hydrogen bonds

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NaCl(sodium chloride)

H2O

Ionic Bonds Are Formed Between Two or More Electrically Unbalanced Atoms (Ions)

Covalent Bonds Are Sharing Arrangements Between Two Atoms

When A Molecule Becomes Polar

Hydrogen Bonds: Bonds Between Polar Molecules

Chemical Reactions

Water’s Life-Supporting Properties

• Cohesion

• Adhesion

• Capillary action

• Surface tension

• Moderates temperature change

• Less dense as a solid

• Universal solvent



Figure 2.16

Water Can Dissolve A Large Number Of Substances

• Water surrounds ions and polar molecules, pulling them apart from each other and dissolving them. Substances that dissolve in water are called hydrophilic.

Table salt

(NaCl) in water

• Water cannot dissolve non-polar (hydrophobic) molecules like oil, fat, and grease.

• Since the majority of substances on earth are hydrophilic, water is called the universal solvent.

H2O H+ + OH-

water hydrogen ion hydroxide ion

Water Breaks Can Break Apart to Form Ions

• When liquid water is pure, it has an equal number of hydrogen and hydroxide ions (H+ = OH-). Pure water is neutral.

• Some substances, when added to water give off H+ and create acidic conditions (H+ > OH-). These substances are acids.

• Other substances when added to water give off OH- and create alkaline or basic conditions (H+ < OH-). These substances are called bases or alkali.

• Organisms cannot survive in acidic or basic conditions because their chemicals are broken apart

The pH Scale Is Used to Measure Acidity or Basicity

Buffers

• Substances called buffers can inhibit pH change when part of a water solution

• Buffers soak up added H+ or OH- like chemical sponges

• Humans have bicarbonate buffer in their blood to prevent pH change when eating and drinking.

essential chemistry for biology chapter 2 elements and the periodic table atoms and subatomic...

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elements atoms apples

mass number

periodic table atoms

heavier elements

similar chemical behavior

different isotopes

biology chapter

cuprumperiodic table