Complete Chapter 2

Temp.

Heating reactants increases rate of a reaction (too high temp. can destroy molecule)

Structural Formula

Hydrogen Gas --> H -H Oxygen Gas --> O=O

Molecular Formula

Hydrogen Gas--> H2 Oxygen Gas--> O2

Why is H2 neutral?

* No net charge (2 protons/ 2 electrons shared) * Octet Rule Satisfied (2 electrons) * No free electrons (paired)

Octet Rule

Atoms tend to establish completely full outer energy level.

3 Factors that affect Chemical Reactions

Temperature, Concentration of Reactants & Products, Catalysts

Mass

The amount of a substance

Weight

The force gravity exerts on the substance

Composite of all p orbitals

The four L-level orbitals compactly fill the space around the nucleus, like two pyramids set base.

Elements

The most common elements inside organisms are not the elements that are most abundant in the earth's crust

Half-Life

The time it takes for one half of the atoms in a sample to decay

Triple Bonds

Those that link the two nitrogen atoms of nitrogen gas molecules

Bohr Model

To visualize individual electrons as following discrete circular orbits around a central nucleus

Daltons

Used to measure mass of atoms and subatomic particles.

Tunneling Microscope

Used to see atoms

Will weight or an object be the same in earth as it is on the moon?

Weight will be greater on earth because the earths gravitational pull is greater than on the moon.

A Compound

When a molecule contains atoms of more than one element

Atomic Energy Levels

When an electron releases energy, it falls to lower energy levels closer to the nucleus

Atomic Energy Levels

When an electron absorbs energy, it moves to higher energy levels farther from the nucleus

Covalent Bonds

When two atoms share one or more pairs of valence electron.

Will mass of a substance on earth be the same as its mass on the moon?

Yes

An Isotope

element that possess different numbers of neutron

Level L

level L,is occupied by four orbitals: one s orbital (referred to as the 2sorbital) and three p orbitals (each referred to as a 2p orbital).

Products

molecules resulting from the chemical reaction as products

Electrons per orbital

no orbital may contain more than two electrons.

Reactants

original molecules before the reaction starts

Radioactive Isotopes

the same chemical element w/ different masses whose nuclei are unstable & dissipate excess energy by emitting radiation in the form of alpha, beta, and gamma rays

A Molecule

Group of atoms held together by energy in a stable association

Elements found significantly in humans?

H, Na, Mg, K, Ca, C, N, O, P, S, Cl

Carbon

Has 3 isotopes, all containing 6 protons. Over 99% of the carbon found in nature exists as an isotope w/ 6 neutron.

Carbon 12

Has 6 protons & 6 neutrons= 12 mass daltons

Carbon 13

Has 6 protons & 7 neutrons= 13 mass daltons

Carbon 14

Has 6 protons & 8 neutrons= 14 mass daltons

Carbon -14 ex.

Has a half-life of 5600 years. 1 gram of carbon-14 today would contain 0.5 gram of car- bon-14 after 5600 years, 0.25 gram 11,200 years from now, 0.125 gram 16,800 years from now.

NaCl (ionic bond)

* Sodium has 11 electrons: 2 in inner energy level, 8 in next level, & 1 in outer (valence) level. * Valence electron is unpaired (free) & strong tendency to join with another electron. *Loss of electron results in the formation of positively charged sodium ion, Na+. * Chlorine atom has 17 electrons: 2 in inner energy level, 8 in next level, and 7 in outer level *Orbital in outer energy level has an unpaired electron. Adding another electron to outer level fills it & causes negatively charged chloride ion, Cl-. * Because opposite charges attract, the Na+& Cl- remain associated in ionic compound, NaCl, (electrically neutral).

> Trace amounts

0.1% or higher

How much does a neutron weigh?

1 dalton

How much does a proton weigh?

1 dalton

How much does an electron weigh?

1/1840 of a dalton

Electron to proton ratio

1:1

1 gram

6.02 × 1023

How many elements?

92

H2 Hydrogen Gas (covalent bond) "Diatomic"

Has an unpaired electron & unfilled outer energy level, so hydrogen atom is unstable. When 2 hydrogen atoms are close to each other, each atom's electron can orbit both nuclei. In effect, the nuclei are able to share their electrons.

Niels Bohr

A 1913 Danish physicist proposed that atoms have an orbiting cloud of electrons.

Cholirine (anion ex.)

A chlorine atom (Cl) that has gained one electron becomes a chloride ion (Cl-), with a charge of -1.

Electronegativity

A measure of the tendency of an atom to attract a bonding pair of electrons.

Isotopes of an Element

Have same arrangement of electrons, so behave the same way chemically

Elementa

All atoms have the same number of protons, but may not have the same number of neutrons.

Sodium (Cat ex.)

An atom of sodium (Na) that has lost one electron becomes a sodium ion (Na+), with a charge of +1.

Anion

An atom that has fewer protons than elec- trons carries a net negative charge

Cation

An atom that has more protons than electrons has a net positive charge

An Element

Any substance that cannot be broken down to any other substance by ordinary chemical means.

Matter

Any substance that has mass and occupies space.

Orbital of that Electron

Area around a nu- cleus where an electron is most likely to be found.

Outer Energy Level

Can contain no more than eight electrons

Ions

Carry an electrical charge

Water

Consists of an oxygen atom bound to two hydrogen atoms by two single covalent bonds

Rate of Decay

Constant for all isotopes

Atomic Number

Dictates number of electron orbiting nucleus (5 protons=5 electrons)

S orbitals

Electron or- bitals near the nucleus are spherical

P orbitals

Electron orbitals shaped like dumb-bells

Valence Electrons

Electrons in the outer energy levels of the different elements

Movement of electron

Electrons keep their energy of position.

Inert, or nonreactive

Elements possessing all eight electrons in their outer energy level (two for helium).

Highly Reactive Elements

Elements with seven electrons in their outer energy level

Volume in an Atom

Empty space, bc the electrons are far from the nucleus relative to its size

Energy Levels

Energy levels, which are drawn as rings to indicate an electron's energy

Atomic Mass

Equal to sum of masses of its protons and neutrons

Highly Reactive Elements Include

Fluorine (F), chlorine (Cl), and bromine (Br).

Salt Crystals (hold NaCl together)

Force exists between any one ion & all neighboring ions of opposite charge, and the ions come together in a mixture

Chemical Reaction

Formation and breaking of chemical bond

Ionic Bond

Forms when atoms with opposite electrical charges (ions) attract.

Reduction

Gain an electron

Inert, or nonreactive elements Include

Include helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn).

Catalyst

Increases rate of reaction. Doesn't alter reaction's equilibrium between reactants & products, but it shortens time needed to reach equilibrium. Proteins called enzymes catalyze almost every chemical reaction.

Chemical Bonds

Ionic Bonds Covalent Bonds

Level K

Level K, lowest energy level or electron shell ( nearest the nucleus). Occupied by a single s orbital, referred to as 1s

What happens with elements with only one electron in their outer shell?

Lithium (Li), sodium (Na), and potassium (K), are also very reactive; they tend to lose the single electron in their outer level.

Oxidation

Loose an electron

Nucleus of an Atom

Made up of Protons and Neutrons.

Carbon

Mixture of isotopes

Ions

Number of electrons does not equal the number of protons

Atomic Nulmber

Number of protons

LOOK AT NaCl Diagram

Online

Single Bond

Only one electron pair is shared

Energy

Orbitals may be the same distance from the nucleus and, thus, contain electrons of the same energy

Orbitals

Orbitals, which have a variety of three-dimensional shapes and indicate an electron's most likely location.

H2O in Electronegativity

Oxygen and the hydrogen atoms attract the electrons they share in the covalent bonds of a water molecule

Concentration ***

Reactions proceed more quickly when more reactants are available. An accumulation of products typically speeds reactions in the reverse direction.

Dimitri Mendeleev 1900s

Russian chemist discovered Octet Rule by arranging elements by mass in periodic table.

Water

Satisfies the octet rule, has no unpaired electrons, carries no net electrical charge

Double bonds

Satisfy the octet rule by allowing two atoms to share 2 pairs of electrons

Protons & neutrons held toegther ONLY over

Short subatomic distances

Atoms

Small particles that make up Matter.

Strength of Covalent Bond

depends on the number of shared electron