Chemistry-Hesi A2 Prep

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The study of the composition, properties and behavior of matter, as well as the interactions between molecules and various forms of energy.

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Chemistry

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The basic unit of chemistry

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The atom

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An attaction between atoms allowing the formation of chemical substances containing two or more atoms.

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Chemical bond

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A form of matter with a constant chemical composition and characteristic properties that can't be separated into components by physical separation methods--e.g. without breaking chemical bonds. May be solid, liquid, gas or plasma.

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Chemical substance

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An electrically neutral group of two or more atoms held together by covalent chemical bonds

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Molecule

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Chemical bond with a stable balance of attractive and repulsive forces resulting from the sharing of electron pairs between atoms

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Covalent bond.

The "valence" is the number of bonds that a given atom can form with one or more other atoms. A "monovalent" atom, ion or group can form one covalent bond. A "divalent" entity has a valence of two.

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Which chemical bonds are considered the "strong" bonds?

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Covalent bonds
Ionic bonds

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Which chemical bonds are considered the weaker bonds?

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Van der Waals force (Dipole-Dipole interactions, London Dispersion Force)
Hydrogen bonding

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Relatively weak chemical bond formed through an electrostatic reaction between two oppositely charged ions due to the attraction between an atom that has lost one or more electons (cation--usually metal), and an atom that has gained one or more electrons (anion--usually a non-metal atom) Easily disrupted by water--as when a salt dissolves.

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Ionic bond

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Chemical bond that results from the sharing of electron pairs between atoms. For many molecules, this sharing of electrons allows each atom to attain the equivalent of a full outer shell, resulting in a stable electronic configuration

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Covalent bond

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A chemical bond resulting from the electrostatic interaction of permanent dipoles in molecules

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Dipole-dipole interaction

A permanent dipole occurs when two atoms in a molecule have substantially different electronegativity--One atom attracts more electrons than another, becoming more negative, while the other becomes more positive. A molecule with a permanent dipole is a "polar molecule"

Not a true bond.

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The weakest chemical bond: The sum of attractive or repulsive forces between molecules or parts of the same molecule, other than those due to covalent bonds, hydrogen bonds, or the electrostatic interaction of ions with one another, neutral molecules or charged molecules.

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Van der Waals force
Includes the Keesom force (interaction between two permanent dipoles), the Debye force (interaction between a permanent dipole and a corresponding induced dipole), and the London dispersion force (interaction between two simultaneously induced dipoles)

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Attractive interaction between polar molecules in which hydrogen is bound to a highly electonegative atom, such as nitrogen, oxygen or fluorine.

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Hydrogen bond.

The hydrogen bond is not a true bond, but a particularly strong dipole-dipole reaction.

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Sharing of electrons in which the positively charged nuclei of two or more atoms simultaneously attract the negatively charged electrons that are being shared between them

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Covalent bond

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One or more electrons unequally shared between two nuclei

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Polar covalent bond

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Outer atomic orbital of one atom has a vacancy which allows the transfer of one or more electrons--one nucleus offers a more tightly bound position to an electron than does the other nucleus. One atom then assumes a net positive charge, and the other a net negative charge, and the bond results from electrostatic attraction between atoms

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Ionic bond

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Each atom in a metal donates one or more electrons to a "pool" of electrons residing between many metal atoms. Each electron in the pool is free (by virtue of its wave nature) to be associated with a great many atoms at once. The bond results because the metal atoms become somewhat positively charged due to loss of their electrons, while the electrons remain attracted to many atoms, without being part of any given atom.

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Metallic bond

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An electrically neutral group of two or more atoms held together by covalent chemical bonds

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Molecule

Complexes or atoms connected by non-covalent bonds (e.g. hydrogen bonds or ionic bonds) are generally not considered single molecules

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Transformation of some substances in to one or more different substances resulting from the rearrangement of chemical bonds between atoms.

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Chemical reaction

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The capacity of a system to perform work (movement of a force across a distance) Cannot be created or destroyed, but may be changed to different forms

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Energy

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Energy of motion (e.g. carried by a moving mass, such as a thrown baseball)

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Kinetic energy

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Energy possessed by an object due to its position in a force-field--e.g. a gravitational, electric or magnetic field

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Potential energy

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The measure of the number of specific ways a system may be arranged--often taken as a measure of disorder, or progress toward a thermodynamic equilibrium

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Entropy

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Anything made of particles having rest mass and volume

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Matter.

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Consists of a dense core (the atomic nucleus) surrounded by a space called the electron cloud.

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Atom

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The nucleus is made of positively charged ____________ and _____________, which have no charge

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Protons, neutrons

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Electrons carry a ____________ charge

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Negative

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The smallest entity that retains the chemical properties of an element (e.g. electronegativity, ionization potential, preferred oxidation states, coordination number, and preferred bond-types)

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Atom

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A pure substance composed of a single type of atom, characterized by a particular number of protons in the nuclei of its atoms.

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Element
(The number of protons in the nuclei is the atomic number)

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Atoms of an element will always have the same number of protons in the nucleus, however, when they have variants in the numbers of neutrons, they are called ____________

Examples of these include Carbon-12, Carbon-13 and Carbon-14.

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Isotopes.

The numbers assigned to the isotope indicate the total number of protons and neutrons in the nucleus--Since carbon's atomic number is 6, Carbon 12, 13 and 14 have 6, 7, and 8 neutrons, respectively.

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The process by which an unstable atom loses energy by emitting particles of ionizing radiation (particles that individually carry enough kinetic energy to liberate an electron from an atom or molecule, ionizing it)

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Radioactivity

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____ naturally occuring elements have been identified, as well as ____ that have been synthesized in a laboratory. Of the naturally occuring elements, ___ are primordial, while the other ___ only occur in decay chains of the primordial elements. Of the ____ confirmed chemical elements, ____ have been recognized and named by IUPAC

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98, 20, 84, 14, 118, 114.

Elements 113, 115, 117 and 118 have reportedly been synthesized in labs, but these reports have not yet been confirmed, and they are known only by their numbers.

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A pure chemical substance consisting of two or more elements combined together. Has a particular ratio of atoms of particular chemical elements that determine its composition and a particular organization that determines its chemical properties.

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A compound

(For example, water is a compound containing hydrogen and oxygen in the ratio of 2:1, with the oxygen atom between the two hydrogen atoms, and an angle of 104.5 degrees between them.)

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A kind of matter with a definite composition and set of properties

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Substance
(e.g. diamond, sucrose, water, sodium chloride, sodium bicarbonate)

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The smallest individual portion of a pure chemical substance that retains its unique set of chemical properties (its potential to undergo certain chemical reactions with other substances)

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Molecule

Not all substances or chemical compounds are comprised of discrete molecules--e.g. the solid substances making up the crust, mantle and core of the earth are chemical compounds without molecules.

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What are the inert (noble) gases?

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Argon, helium, neon, krypton, xenon and radon

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Unit of measurement denoting an amount of substance (chemical amount) --specifically the amount of a substance the contains as many elementary entities (atoms, molecules or ions) as there are atoms in 12 grams of carbon-12, where the carbon-12 atoms are unbound, at rest and in their ground state

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Mole

The concentration of a solution is often expressed by its molarity--defined as the number of moles of the dissolved substance per liter of solution.

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A charged species, an atom or a molecule that has lost or gained one or more electrons

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An ion

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An atom that has lost an electron, and has more protons than electrons

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Postively charged ion, or cation

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An atom that has gained an electron, and has more electrons than protons

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A negatively charged ion or anion

Front 41

Applying Arrhenius theory, ___________ substances produce hydronium ions when dissolved in water.

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Acid

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Applying Arrhenius theory, _________ substances produce hydroxide ions when dissolved in water.

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Base

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Acid strength is most commonly measured by_____, the measurement of ____________ ion concentration in a solution, as expressed on a negative logarithmic scale.

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pH, hydrogen ions (hydronium ions)

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Substances with a _______ pH, have a high hydronium ion concentration and are more _________

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Low, acidic

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A set of states of a chemical system that have similar bulk structural properties, over a range of conditions such as temperature or pressure.

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Phase.

Common phases include liquid, solid and gas. Less common phases include plasmas, Bose-Einstein condensates, and fermionic condensates, and the paramagnetic and ferromagnetic phases of magnetic materials.

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The transformation of a chemical substance as a result of its interaction with another substance or with energy

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Chemical reaction

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Common chemical reactions include:

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Oxidation
Reduction
Dissociation
Acid-Base Neutralization
Molecular Rearrangement

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An exergonic reaction in which a molecule loses electrons and releases energy.

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Oxidation
(Oxidation is loss (of electrons))-OIL

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An endergonic reaction in which a molecule gains electrons and energy

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Reduction
(Reduction is gain (of electrons))- RIG

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A general process in which ionic compounds (complexes or salts) separate or split into smaller particles, ions or radicals--usually in a reversible manner.

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Dissociation

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An acid and a base react to form a salt, and frequently water as well.

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Acid-Base Neutralization

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Neutralization reactions are frequently _________________

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Exothermic--releasing energy from a system, usually in the form of heat, but also as light (a spark, flash or flame), electricity (a battery) or sound (e.g. as in an explosion)

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The reaction between baking soda and vinegar is an example of an _____________ neutralization reaction.

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Endothermic--the system absorbs energy from its surroundings in the form of heat.

Front 54

Neutral pH is:

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7

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Redox reactions

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All chemical reactions in which atoms have their oxidation state changed either by gaining electrons (reduction) or losing electrons (oxidation)

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The state, in a chemical reaction, in which both reactants and products are present at concentrations that have no further tendency to change with time--usually occuring when the forward reaction proceeds at the same rate as the reverse reaction.

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Equilibrium

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An attribute of a substance as a consequence of its atomic, molecular, or aggregate structure.

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Energy

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Reactions where there is a net release of energy, and the products have less total free energy than the reactants did.

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Exergonic (exothermic reactions)

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A reaction is ____________ if the final state is higher on the energy scale than the initial state.

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Endergonic (e.g. an endothermic reaction, where the reaction absorbs heat from the surroundings)

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Sharing of one electron pair between nuclei

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Single covalent

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Sharing of two electron pairs

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Double covalent.

Frequently occurs between carbon atoms--carbon and oxygen, carbon and nitrogen.

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Covalent bond in which electrons are equally attracted to both nuclei--may be single or double.

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Non polar covalent

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Covalent bond in which electrons are slightly more attracted to one nucleus than the other, resulting in slightly positive and negative regions in one molecule

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Polar covalent

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Sum of atomic weights of component atoms

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Molecular weight (of a compound)

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Molecules with identical molecular formulae, but different arrangements

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Isomer

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5 Biologically important properties of water

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Solvency
Adhesion
Cohesion
Chemical Reactivity
Thermal Stability

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The ability to dissolve other chemicals

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Solvency

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Adhesion

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The tendency of one substance to cling to another

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Cohesion

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The tendency of molecules of the same substance to cling to each other

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The ability to participate in chemical reactions

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Chemical reactivity

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Thermal stability

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Result of high specific heat (the amount of heat necessary to raise the temperature of 1g of that molecule by 1 degree)

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Decomposition

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An exergonic reaction, such as digestion and cell respiration, in which larger molecules are broken down into smaller ones.

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Catabolism

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An exergonic reaction and the sum of all decomposition reactions in the body

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A molecule that donates electrons to another

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Reducing agent

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The number of protons in an atom

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The atomic number

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The number of electrons is equal to the number of __________

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Protons

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Atomic weight is determined by

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The number of protons plus the number of neutrons

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Relative atomic mass

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The same as the atomic weight, although typically rounded to the nearest whole number