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