KEAN BIO 1000 - Chemistry Of Life

Unformatted text preview:

CONCEPTUAL LIFE SCIENCE CHEMISTRY OF LIFE Chemistry is the study ofmatter Life science involves the study ofliving things. Since living things are made of matter, knowledge of simple chemistry will help you to understand the principles underlying the structure and activities ofliving things. ATOMS The atom is the smallestquantityofan elementthatstillpossessestheproperties ofthe element. The nucleus ofthe atoms contains the protons and the neutrons. The electrons are found in shells that surround the nucleus. Table Ill-} contains infonnation about the fundamental particles ofthe atom. Table III-I. Fundamental particles ofthe atom. Symbol Particle Charge Mass e Proton +1 1AMU· 0 .Neutron 0 1AMU • Electron ·1 6.6 x 10-4AMU ·AMU II Atonllc Mass Unit Examples ofatomic structure Hydrogen Hydrogen is the first and simplest element. In the nucleus it has one proton. In the electron shell is one electron. For hydrogen the atomic number is 1 and the mass is ]. 3-] { .3-2 Hydrogen Chemical StructureSymbol Figure 3-1. Formula and structure ofhydrogen. The atomic number is represented by the lower number and the atomic mass is represented by the upper number. Helium .Helium is the second element. In the nucleus it has two protons and two neutrons. There are two electrons in the electron shell. For helium. the atomic number is 2 and the mass is 4. Helium Chemical StructureSymbol Figure 3-2. Fonnula and structure ofheJium. Lithium Lithium is the third element. Its nucleus has three protons and four neutrons. There are two electrons in the first shell and one electron in the second shell.. 1bis is becausetherustshellonlyholdstwoelectrons. Thecapacityofthesecondshelliseight. electrons.3-3 Lithium Chemical StructureSymbol -7 3 LI Figure 3-3. Formula and structure oflithium. Lithium has two electron shells because the first shell only holds two electrons. Carbon Carbon is element number 6. It has six protons and six neutrons. There are six electrons, two in the :first shell and four in the second sheli. Its atomic number is 6 and its mass is 12. . Carbon Chemical Structur.eSymbol. Figure 3-4. Formula and structure ofcarbon. Oxygen Oxygen is element number 8. It has eight protons and eight neutrons in its nucleus. It has eight electrons, two in the first she)) and six in the secondshell•.Its . atomic number is 8 and its mass is 16.• • • •• 3-4 Oxygen Chemical structureSYlnbol Figure 3-5. Fonnula and structure of oxygen. Note that the electrons in the outer shell are distributed lDlevenly. There are two pairs ofelectrons and two single electrons. This distribution is important in the way that oxygen bonds to other atoms. Dot structures The outer electrons are all that matter in chemical bonding. It is customary to represent them using dots. •C·• 0 :. Figure 3-6. Dot structures. The electrons in the outer she)) are represented using dots. These dot structures assist in understanding chemical bonding. Elements Elements are chemical substances composed of only one type ofatom. There are over100elements. TheelementsareorganizedintothePeriodicTableoftheElements.• • • • • • 3-5 Tabe -. e ements mprotoplasm. Element Hydroaen OxYRen Carbon Nitrogen Phosphorus Sulfur IIIJ2P"allnnclpl I Symbol Percentage H 63 0 25.5 C 9.5 N 1.4 P <1 S <1 Molecules Molecules are electrically neutral aggregates ofatoms bonded together. "Electrically neutral" means that the numberofprotons equals the number ofelectrons. Compounds Compounds are substancescomposedofa singlekindofmolecule. They can be broken down into simpler substances. For example, water (H20) can be decomposed into hydrogen and oxygen. Sodium chloride (NaCI) can be decomposed into sodium and . chlorine atoms. CHEMICAL BONDS We are concerned with two kinds ofbonds: ionic bonds and covalent bonds. . -Atoms behave in a way that gives them a complete outer shell. These -bonding methods achieve that goal. Ionic bonds ionic bonding: Before Na .~~-__•. ·CI: Ionic bondi,. After • • - Na + :CI: Figure 3-7. Formation ofan ionic bonet.• • • • . . 3-6 Ionicbondsareformed by completetransferofoneormoreelectrons from one atom to another. An example is the formation ofsodium chloride (table salt). Covalent bonds COVillent bonding: Before CO'VIIlent bond"1ftIP Af.... HH:O : Figure3-8. Fonnationofa covalentbonds. Covalentbondsareformedbysharingofelectronsbetweenatoms. Abondis fonnedwhenapair ofelectronsisshared. EachatomgetstoshaleenoughelectroBsto give it a complete outer shell. Some Biologically Important Compounds Water Cal"boD Dioxide o=C=o O~'geu (8 diatomic molecule) 0=0 Sodium Chloride NaCI Figure 3-8. Some biologically important compounds. Water and salts are examples ofinorganic compounds. .3-7 THE pH SCALE Ionization Molecules ofionic compounds contain ions. Ions are fonned by complete transfer of electrons from one atom to another. You will recall that in the formation of sodium chloride (NaCI), one electron was transferred from sodium to chlorine. The result was fonnation ofasodium ion(Na') andachlorideion (CI"). When salt is dissolved in water, the ions separatejrom each other. The result is that the positive; sodium ions and the negative chloride ions move around among the water . molecules as separate charged particles. Water can ionize. Despite being a covalent compolDld, water can dissociate to a slight extent to form ions. The result is that the water molecule (H20) fonns hydrogen ions . (H) and hydroxide ions (OH"). . NeutralizatioD Acidsform hydrogen ions. Whtm an acid compound ionizes, it will form hydrogen ions. For example, hydrochloric acid (HCl): HCl? w+cr Basesform hydroxide ions. When a basic compound ionizes, it will form hydroxide ions. For example, sodium hydroxide (NaOH): NaOH ~Na+ +OH" Neutralization is a reaction between an acid and a base. When an acid and a base react, the hydrogen and hydroxide ions combine to produce water. The other ions combine to produceasalt. Asaltisformedbythepositiveionofthebaseandthenegativeionofthe acid. For example: NaOH + Hel ~ HOH + NaCl Neutralization has some important applications. You use vinegar (a weak acid) or boric acid to partly neutralize oven cleaner (a strong base). lt~an be used iflye (NaOH) is spilled on the skin while cleaning a drain. Farmers will add limestone to the soil ifit is too acidic. Many over-the-counter products contain sodiwn bicarbonate (a weak base) to neutralize "excess stomach acid". Sodium bicarbonate is produoed in


View Full Document

KEAN BIO 1000 - Chemistry Of Life

Download Chemistry Of Life
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view Chemistry Of Life and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Chemistry Of Life 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?