High School Chemistry

Based on Khan Academy's High School Chemistry Course

Atom

A basic unit of matter made of subatomic particles (protons, neutrons, and electrons)

Nucleus

Protons and neutrons in the middle of an atom

Electron cloud

Where electrons are most likely to be found

Proton

Subatomic particle with a charge of 1+ and a mass of 1 unified atomic mass unit (u)

Electron

Subatomic particle with a charge of 1- and a mass of 0.0005 unified atomic mass unit (u)

Neutron

Subatomic particle with a neutral charge and a mass of 1 unified atomic mass unit (u)

What is an element identified by?

The number of protons in its nucleus

Abbreviation for atomic number

Z

Atomic number

The number of protons

Chemical symbol

Every element's unique one or two letter abbreviation

Isotopes

Atoms of the same element with different numbers of neutrons

Mass number

The sum of the number of neutrons and protons in an atom

Isotope notation

Ion

An atom with an electric charge

Cation

A positively charged ion with more protons than electrons

Anion

A negatively charged ion with more electrons than protons

How is the charge of an ion calculated?

# of protons - # of electrons

Bohr Model

Electrons are represented as dots that sit on a ring around the nucleus

Energy Levels/Shells

The circles in a Bohr Model

How many electrons can each energy level in an atom hold?

1st = 2, 2nd = 8, 3rd = 18, 4th = 32

Valence shell

The outermost shell in an atom

Valence electrons

The outermost electrons of an atom (found in the valence shell)

Core electrons

Electrons that are not in the valence shell

Radiation

Energy that travels through space

Electromagnetic radiation

Energy transferred by oscillations in the electromagnetic field

Photon

A particle of EM radiation

Speed of light in a vacuum (c)

3 × 10⁸ m/s

Wavelength

The distance from one peak of a wave to the next peak

Frequency

The number of wave cycles in a period of time

Relationship between photon energy and frequency

Photon energy increases as frequency increases

Electromagnetic radiation types from lowest frequency to highest frequency

Radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays

How do emission spectra occur?

Energized electrons drop an/multiple energy levels, releasing photons

How do absorption spectra occur?

Cool gas absorbs photons in order for its electrons to jump up energy levels

Lewis dot diagrams

Diagrams that consist of the chemical symbol of an element surrounded by dots for each of the valence electrons that the element has

Orbitals

Areas where electrons are likely to be found

1s orbital

2s orbital

2p_x orbital

2p_y orbital

2p_z orbital

When discussing orbitals, what represents energy levels?

The coefficient

Subshell

2s is a subshell, 2px, 2py, and 2pz make up a subshell

Electron configurations

Where electrons are located around the nucleus of an atom

What do the exponents in electron configurations mean?

How many electrons are in each subshell

Aufbau principle

Electrons fill lower-energy atomic orbitals before filling higher-energy ones (works best for the first 20 elements)

Which electron configuration block is this? (blue)

s-block

Which electron configuration block is this? (pink)

d-block

Which electron configuration block is this? (green)

p-block

Which electron configuration block is this? (yellow)

f-block

How to write electron configuration in shorthand?

Write the electron configuration for the previous noble gas

Octet rule

Most of the elements important in biology need 8 electrons in their outermost shell in order to be stable

Groups

The vertical columns on the periodic table

Periods

The horizontal rows on the periodic table

Alkali metals

Group 1 on the periodic table

Alkaline earth metals

Group 2 on the periodic table

Halogens

Group 7 on the periodic table (very reactive nonmetals)

Noble gases

Group 8 on the periodic table (very unreactive)

Going across a period, atomic radius tends to… (and why)

Decrease because of increased nuclear charge (more proton pull)

Going down a group, atomic radius tends to… (and why)

increase due to increased shielding and the addition of new shells

Ionization

The process of removing an electron from a neutral atom or compound

Ionization energy

The energy required to remove an electron

Going across a period, ionization energy tends to… (and why)

Increase (more proton pull)

Going down a group, ionization energy tends to… (and why)

Decrease (more orbital rings so more shielding)

How can the charge of an atom be predicted?

How many electrons an atom needs to gain or lose in order to achieve a full octet

Ionic bonds

The attraction between oppositely charged ions

What structure is an ionic solid?

Crystal lattice structure

Advantage of a lattice structure for ionic solids

Maximizes the attractive forces between opposite charges and minimizes the repulsive forces between like charges

How are cations named?

Element name + "ion" (ex: sodium ion)

Polyvalent

Able to form cations of different charges

How is the magnitude of charges for polyvalent ions represented?

Roman numerals

How are anions named?

Root of the element's name + ide

Monatomic ions

A single atom with a net charge

Polyatomic ions

A group of atoms with a net charge

Hydroxide chemical formula and charge

OH^-, with a charge of -1

Acetate chemical formula and charge

C₂H₃O₂^-, with a charge of -1

Nitrite chemical formula and charge

NO₂^-, with a charge of -1

Nitrate chemical formula and charge

NO₃^-, with a charge of -1

Carbonate chemical formula and charge

CO₃^-2, with a charge of -2

Sulfite chemical formula and charge

SO₃^2-, with a charge of -2

Sulfate chemical formula and charge

SO₄^-2, with a charge of -2

Phosphate chemical formula and charge

PO₄^3-, with a charge of -3

Ammonium chemical formula and charge

NH₄⁺, with a charge of +1

Cyanide chemical formula and charge

CN^-, with a charge of -1

Bicarbonate chemical formula and charge

HCO₃^-, with a charge of -1

Hypochlorite chemical formula and charge

ClO^-, with a charge of -1

Chlorite chemical formula and charge

ClO₂^-, with a charge of -1

Chlorate chemical formula and charge

ClO₃^-, with a charge of -1

Perchlorate chemical formula and charge

ClO₄^-, with a charge of -1

Permanganate chemical formula and charge

MnO₄^-, with a charge of -1

Chromate chemical formula and charge

CrO₄^2-, with a charge of -2

Dichromate chemical formula and charge

Cr₂O₇^2-, with a charge of -2

Hydrogen Peroxide chemical formula and charge

H₂O₂, with a charge of 0 (each oxygen atom has a charge of -1 and each hydrogen atom has a charge of +1)

The atoms within a polyatomic ion molecule are held together by…

Covalent bonds

When naming acids, if the name of the anion ends in the -ide suffix

Write as hydro---ic acid

When naming acids, if the name of the anion ends in the -ate suffix

Write as ---ic acid

When naming acids, if the name of the anion ends in the -ite suffix

Write as ---ous acid

Covalent bonds

Shared electron pairs between atoms

Molecule

A group of two or more atoms covalently bonded together

Diatomic elements

Elements that do not exist alone in nature as individual atoms, and are found as a covalently-bonded pairs

Compound

A chemical substance composed of two or more different elements