Unit 3 Honors Chemistry Review

Atom

The smallest unit of an element that retains its chemical properties.

Proton

• positive charged

• in nucleus

• 1 amu

Neutron

• neutral particle

• in nucleus

• 1 amu

Electron

• negatively charged

• in orbitals

• very small mass

Nucleus

The dense, positively charged center of an atom containing protons and neutrons.

Atomic Number

The number of protons in an atom.

Mass Number

The total number of protons and neutrons in an isotope.

Isotope

An atom of the same element with a different number of neutrons.

Ion

An atom that has gained or lost electrons and has a net charge.

Cation

A positively charged ion formed by losing electrons.

Anion

 A negatively charged ion formed by gaining electrons.

Neutral Atom

An atom with equal numbers of protons and electrons.

Gold Foil Experiment

 Rutherford's experiment showing that atoms are mostly empty space with a small, dense, positively charged nucleus.

Isotope Notation

 A way of representing an isotope using its element symbol, mass number, and atomic number.

Average Atomic Mass

 The weighted average of the masses of an element's naturally occurring isotopes.

Percent Abundance

 The percentage of an element's atoms that are a particular isotope.

Weighted Average

An average that accounts for how frequently each value occurs.

Aufbau Principle

 Electrons fill the lowest-energy orbitals first.

Pauli Exclusion Principle

 Each orbital can hold a maximum of two electrons with opposite spins.

Hund’s Rule

Electrons occupy equal-energy orbitals singly with parallel spins before pairing.

Electron Configuration

A notation showing how electrons are distributed among an atom's energy levels and sublevels.

Abbreviated Electron Configuration

An electron configuration that uses the previous noble gas in brackets to represent inner electrons.

Orbital Diagram

A diagram using boxes or lines for orbitals and arrows for electrons.

Orbital

A region around the nucleus where an electron is likely to be found.

Principle Energy Level

 A main electron energy level, represented by the number .

Sublevel

 A subdivision of an energy level labeled s, p, d, or f.

Ground State

 The lowest-energy arrangement of an atom's electrons.

Excited State

 A state in which one or more electrons occupy higher-energy positions than in the ground state.

Electron Spin

 A quantum property of electrons represented by up and down arrows in orbital diagrams.

Noble Gas Configuration

 An abbreviated electron configuration using a noble gas to represent inner electrons.

s Sublevel

 Contains 1 orbital and holds a maximum of 2 electrons; its orbital is spherical.

p Sublevel

 Contains 3 orbitals and holds a maximum of 6 electrons; its orbitals are dumbbell-shaped.

d Sublevel

 Contains 5 orbitals and holds a maximum of 10 electrons; its orbitals are mostly cloverleaf-shaped.

f Sublevel

 Contains 7 orbitals and holds a maximum of 14 electrons.

Orbital Capacity

 The maximum of 2 electrons that can occupy a single orbital.

Electron Filling Order

The order in which sublevels fill from lower to higher energy: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, and so on.

Wavelength (lambda)

 The distance between matching points on consecutive waves; measured in meters.

Frequency (v or f)

 The number of wave cycles passing a point each second; measured in hertz (Hz).

Electromagnetic Radiation

Energy that travels through space as oscillating electric and magnetic fields.

Photon

A discrete packet of electromagnetic energy.

Speed of Light c

The speed of light in a vacuum, approximately  m/s.

Inverse Relationship

A relationship in which one quantity increases as the other decreases; wavelength and frequency are inversely related for light in a vacuum.

Visible Spectrum

 The portion of electromagnetic radiation that human eyes can see.

Red Light

Visible light with the longest wavelength and lowest frequency.

Violet Light

 Visible light with the shortest wavelength and highest frequency.

Electron Transition

 A change in an electron's energy level.

Emission

The release of energy as an electron moves from a higher to a lower energy level.

Absorption

 The gaining of energy by an atom, allowing an electron to move to a higher energy level.

Excited Electron

An electron occupying a higher-energy state than its ground-state position.

Electromagnetic Spectrum

 The full range of electromagnetic radiation, from radio waves to gamma rays.

Neutron Formula

 Number of neutrons = mass number − atomic number.

Avg Atomic Mass

Average atomic mass = sum of (isotope mass × fractional abundance).

Wave Equation

c= lambda/v where c  is the speed of light, lambd.  is wavelength, and v is frequency.

Wavelength Formula

c= lambd./v

Frequency Formula

-v= c/lambd.

Nanometer (nm)

 A unit of length equal to  meters.

Hertz (Hz)

The unit of frequency; one hertz equals one cycle per second.

Most Abundant Isotope

 The isotope present in the greatest proportion; its mass is generally closest to the average atomic mass.

Visible Light Order

 Red, orange, yellow, green, blue, indigo, violet, from longest to shortest wavelength.