AP Chem Unit 1

Mole

amount of substance containing the same number of discrete entities (atoms, molecules, ions) as the number of atoms in a sample of pure Carbon-12

Molecular Weight

the sum of the atomic weights of the atoms in the chemical formula of the substance, covalent

Basic Atomic Structure

dense positive center with electrons around the outside, most of atom is empty space, protons/neutrons have essentially same mass (relative mass=1, electron relative mass =0)

Mass Number

total number of protons and neutrons in the nucleus of an atom

Isotope

atom of the same element with different masses

Mass Spectrophotometer

instrument used to measure the precise masses and relative amounts of atomic and molecular ions; five steps: vaporization, ionization, acceleration, deflection, detection

Pure Substance

matter that has a fixed composition and distinct properties, can be either an element or a compound

Law of Definite Proportion

law that states that the elemental composition of a substance is always the same

Formula Weight

sum of the atomic weights for the ions (atoms) in a chemical formula, ionic

Percent Composition

percent of the total mass of the compound that is due to that component

Empirical Formula

the simplest ratio of one element to another in a compound

Molecular Formula

the actual formula of the substance

Element

a substance which can not be decomposed to simpler substances

Compound

a substance which can be decomposed to simpler substances because it is made up of more than one element, have definite composition

Mixture

exhibit properties of the substances that make them, can vary in composition (heterogeneous) or can have same composition (homogeneous) throughout the sample

Elemental Analysis

to determine the quantity of a particular element within a molecule or material, qualitative (WHAT elements) or quantitative (HOW MUCH of elements)

Bohr's Model

electrons exist only in certain discrete energy levels (quantum numbers), energy is involved in the transition of an electron from one level to another, WRONG: only works for hydrogen, classical physics says the electron should fall into the nucleus, circular motion is not wave-like in nature

Quantum Mechanical Model

Schrodinger/Heisenberg, mathematical treatment that incorporates both the wave and particle nature of matter, the more precisely the momentum of a particle is known the less precisely its position is known

Quantum Numbers

by solving Shrodinger's equation 4 of these describe the probable location of the electrons around the nucleus of an atom

S Orbital

one, spherical, radius increases with value of n

P Orbital

three, have two lobes with a node between them

D Orbital

five, four of the five have four lobes and the other resembles a p orbital with a donut around the center

F Orbital

seven, very complicated shapes

Energy Levels (Shells)

different distances from the nucleus, each has a combination of different shapes possible, as number of electrons increases so does repulsion between them, start to overlap in energy

Electron Configuration

the way electrons are distributed in an atom, most stable organization is the lowest possible energy called ground state

Aufbau Principle

build electron configurations as we go from atom to atom, fill orbitals in order of increasing energy

Hund's Rule

every orbital in a sublevel is singly occupied before any orbital is doubly occupied, all of the electrons in a singly occupied orbital have the same spin

Pauli Exclusion Principle

no two electrons in the same atom can have the same set of four quantum numbers (opposite spins if in same orbital), no two electrons can have the exact same energy

Main Group Elements

s and p blocks on the periodic table

Chromium Exception

[Ar] 4s1 3d5

Electromagnetic Radiation

covers wide spectrum of wavelengths and frequencies, carried by photons, travels at the same speed through a vacuum

Wave-Particle Duality

where EM radiation and matter can each be explained as particles or waves depending on the experiment

Coulomb's Law

the strength of the interaction between two electrical charges depends on the magnitudes of the charges and on the distance between them

Effective Nuclear Charge

electrons are both attracted to the nucleus and repelled by other electrons (forces an electron experiences depend on both), periodic property: increases across a period, increases slightly down a group. Electrons further from nucleus are partly "shielded" by core electrons, electrostatic repulsion from core electrons reduces electrostatic attraction between outer electrons and proton in nucleus, outer electrons are pushed away, result is protons in nucleus cannot hold on to outer electrons as tightly as core electrons

Ionization Energy

minimum energy required to remove an electron from the ground state of a gaseous atom or ion, the higher this is the more difficult it is to remove an electron, depends on effective nuclear charge/average distance of the electron to the nucleus

Photoelectron Spectroscopy

an experimental technique that measures the relative energies of electrons in atoms or molecules

Photoelectric Effect

emission or ejection of electrons from the surface of, generally, a metal in response to incident light

Photoionization

works by ejecting electrons from the materials using high energy electromagnetic radiation (UV or X-ray) and then measuring the kinetic energy of the electrons

Dmitri Mendeleev

created periodic table based on atomic mass

Henry Moseley

developed concept of atomic number and created new periodic table based on that

Periodicity

repetitive pattern of a property for elements based on atomic number, allows us to predict properties of atoms without direct observation/masurement

Periodic Properties

atomic radii, ionic radii, ionization energy, electron affinity, electronegativity

Coulombic Attraction

electrostatic attraction between two charged particles

Atomic Radius

one half of the distance between covalently bonded nuclei, decreases from left to right across a period and increases from top to bottom of a group because of effective nuclear charge/more energy levels

Ionic radius

determined by interatomic distances in ionic compounds, ionic size depends on nuclear charge, number of electrons, and orbitals in which electrons reside

Cations

smaller than parent atoms, outermost electron is removed and repulsions between electrons are reduced

Anions

larger than parent atoms, electrons are added and repulsions between electrons are increased

First Ionization Energy

energy required to remove the outermost electron from the gas form of a neutral atom in its ground state, increases across a period and decreases down a group

Ionization Energy Exceptions

trend is not followed when added valence electron in next element enters a new sublevel, is the first electron pair in one orbital of the sublevel

Electron Affinity

energy change accompanying the addition of an electron to a gaseous atom, neutral atom's likelihood of gaining an electron, increases across a period, slight decrease down a group, more negative affinity means greater attraction

Electronegativity

ability of an atom in a molecule to attract electrons to itself, increases across a period and decreases down a group

Valence Electrons

electrons found in the highest energy level, outer shell electrons, determine if it is likely that a chemical bond will form between two elements

Ions

atoms that have gained or lost electrons, atoms form these to achieve electron configuration closest to noble gas

Mass Spectrum

gives information on the naturally occurring isotopes of that element, gives number of isotopes present, atomic mass of each isotope, and relative amount of each isotope

Law of Constant Composition

ratios of the masses of the constituent elements in any pure sample of that compound is always the same