Unit 1: Matter, Chemical Trends &Bonding; Wave Mechanical (Quantum) Model of the Atom chem ap

Quantitative Measurements

Quantitative Measurements

Measurements in an experiment made using various tools to measure volume, mass, temperature, etc.

Continuous Data

Quantitative data with associated uncertainty, reflected in significant digits.

Discrete Data

Quantitative data involving counting, exact values with potential experimental error.

Significant Digits

Digits in a measurement that carry forward in calculations, determined by the precision of the measuring tool.

rules of significant digits

1. All nonzero numbers are significant
2. Sandwiched zeros (zeros between 2 nonzero numbers) are significant
3. Zeros after the decimal point are significant
4. Zeros used to locate the decimal point are not significant

addition and subtraction rule

the result carries the same number of decimal places as the quantity with the fewest decimal places

multiplication and division rule

the result carries the same number of significant figures as the factor with the fewest significant figures

Accuracy

Closeness of measurements to an accepted true value.

Precision

Reproducibility or closeness of measurements to each other.

Sensitivity

Ability of an analysis to detect positive cases correctly (true positive rate).

Specificity

Ability of an analysis to detect negative cases correctly (true negative rate).

Accuracy Rate

Percentage of correct results in an analysis.

Precision Rate

Percentage of reproducible results in an analysis.

Pure Substances

Homogeneous substances composed of a single type of atom or molecule.

element

A pure substance made of only one kind of atom

Compund

A substance made up of atoms of two or more different elements joined by chemical bonds

Mixtures

Substances with heterogeneous composition, composed of more than one type of pure substance.

Element

A pure substance consisting of only one type of atom.

Compound

A pure substance composed of two or more elements in a fixed ratio.

Atom

The basic unit of matter, indivisible and retaining the properties of an element.

Isotopes

Atoms of the same element with different numbers of neutrons in the nucleus.

Atomic Mass

The sum of protons and neutrons in an atom's nucleus, expressed in atomic mass units.

average atomic mass

the weighted average of the atomic masses of the naturally occurring isotopes of an element

Alpha Particles

Helium nuclei with a mass number of 4 and atomic number of 2, emitted during alpha decay.

Beta Particles

High-energy electrons emitted during beta decay, causing the atomic number to rise by 1.

Positrons

Particles with the same mass as an electron but a positive charge, emitted during certain types of radioactive decay.

Protons

Nuclei of hydrogen atoms with a positive charge and a mass number of 1.

Neutrons

Neutral subatomic particles with a mass number of 1, found in the nucleus of atoms.

Gamma Rays

High-energy electromagnetic radiation emitted during nuclear reactions.

nuclear reactions

A reaction that involves splitting the nucleus of an atom or fusing two nuclei; these reactions produce much more energy then chemical reactions. balance atomic number and atomic mass

Alpha Decay

A type of radioactive decay where an alpha particle is emitted, reducing the mass number by 4 and atomic number by 2.
-most radioisotope atoms with an atomic number over 82 undergo alpha decay

Beta-Decay

A type of radioactive decay where a neutron changes into a proton, increasing the atomic number by 1.
-happens if too many neutrons in nucleus

positron decay

a nuclear reaction in which a positron is emitted
-happens when too few neutrons compared to number of protons

Fusion

A nuclear reaction where two nuclei combine to form a heavier nucleus, releasing a large amount of energy.

Transmutation

The process of creating a new isotope by inducing a small particle to react with a starting isotope.

Gamma Emission

The release of gamma radiation from a nucleus without any change in atomic or mass numbers.

fission reactions

bombarding nucleus with small high energy particle to break nucleus into two isotopes

first identified radioactive element

polonium (Po)

Radioisotopes

Isotopes that exhibit radioactive decay and are used in various applications.

Half-Life

The time taken for half of the radioactive nuclei in a sample to decay.

unstable isotope

An isotope in which the nucleus is likely to break apart, nucleus is too big, weak electromagnetic force.
-elements over bismuth ((83)

Geiger Counter

A device used to detect and measure ionizing radiation.

Gamma Emitter

Emits gamma radiation, used in medical imaging

Alpha Source

Emits alpha particles, used for direct irradiation in cancer treatment

Beta Source

Emits beta particles, used in medical applications

Decay of Radioisotopes

Process of unstable isotopes spontaneously emitting radiation

John Dalton atomic theory (1803)

the "billiard ball" model of the atom
different atoms were represented by different spheres that could be joined to make molecules in specific ratios; atoms are indivisible
chemical reactions were rearrangments

jj thomson (1904)

discovered that atoms consist of smaller particles (pos + neg)
cathode ray experiment: particles ejected from neutral material between two plates, and were attracted to the negative plate
-plum pudding model

Ernest Rutherford (1911)

found the nucleus; gold foil experiment, used (positive) alpha particles and a narrow beam of particles directed at a sheet of gold foil, most particles went through undected by few bounced back randomly with high energy.
-atom is mostly empty space

Bohr(1913)

planetary model of the atom
-Extended rutherfords model
-discovered electrons exist in specific orbits around nucleus
-birth of quantum mechanical model

Schrodinger

-electons exist in region of space around nucleus according to specific mathematical wave functions.
-electron cloud model wave functions represents probability of locating electrons

Heisenberg uncertainty principle

it is impossible to know exactly both the velocity and the location of a particle at the same time

electron configuration

orbitals

regions around the nucleus in which given electron or electron pair is likely to be found
(s, p, d, f** g,h,i,etc)

Aufbau Principle

An electron occupies the lowest-energy orbital until full, then fills next sublevel

pauli exclusions principle

each orbital can hold max 2 electrons with opposite spins

Hund's Rule

electron in the same sub level (ex. 2s) will be added 1st with one spin direction in each orbital, and then filling the orbitals with electron of opposite sign

quantum numbers

Set of numbers used to completely describe an electron

principal quantum number (n)

symbolized by n, indicates the main energy level occupied by the electron

secondary quantum number (l)

the quantum number that describes the shape and energy of an atomic orbital, with whole-number values from 0 to n-1 for each value of n

magnetic quantum number (m sub l)

magnetic Orientation of electron in 3d orbital (from +l to -l)
-magnetic quantum number represents numbers of orbitals

spin quantum number (m sub s)

either +1/2(clockwise) or -1/2(counter-clockwise), indicating the spin orientation of an electron

atomic radius trend

increases down a group, decreases across a period
-more protons: more attraction from electrons, decreases radius
-more electrons: repulsions, increases radius

ionization energy trend

decreases down a group,increases across a period
-amount of energy required to remove outermost electron
-as atomic radius decreases, ionization energy increases
-as atomic radius increases, effective nuclear charge lessens, ionization energy decreases

electron affinity trend

decreases down a group increases across a period,
-measure of energy that is either released or absorbed during addition of an electron
-more negative energy indicates increased electron affinity
-main group non-metals except noble gases have high electron affinity

electronegativity trend

decreases down a group, increases across a period
-measure of atom's ability to attract electrons in a chemical compound
-elements with greater effective nuclear charge will display higher electronegativity

nuclear effective charge

a representation of average electrical field experienced by a single electron. average environment created by nucleus and other electrons in molecule