ultimate chemistry regents study guide(basic essentials)

Nucleons

Protons and neutrons located in an atom’s nucleus.

Electrons

Small, negatively charged ($-$) particles found in "clouds" (orbitals) around an atom’s nucleus.

Orbitals

The "clouds" around an atom’s nucleus where electrons are found according to the current wave-mechanical model.

Mass number

The sum of an atom’s number of protons and neutrons.

Atomic number

A value equal to the number of protons in the nucleus of an atom.

Number of neutrons

Calculated by subtracting the atomic number from the mass number.

Isotopes

Atoms with equal numbers of protons but different numbers of neutrons.

Cations

Positive ($+$) ions formed when a neutral atom loses electrons; they are smaller than their parent atom.

Anions

Negative ions formed when a neutral atom gains electrons; they are larger than their parent atom.

Ernest Rutherford’s gold foil experiment

An experiment showing that an atom is mostly empty space with a small, dense, positively-charged nucleus.

J.J. Thompson

The scientist who discovered the electron and developed the "plum-pudding" model of the atom.

Dalton’s model

An atomic model described as a solid sphere of matter that was uniform throughout.

Bohr Model

An atomic model that placed electrons in "planet-like" orbits around the nucleus.

STP

Standard Temperature and Pressure, defined as $273 Kelvin$ and $1 atm$.

Bright line spectra

Light produced when electrons emit energy as they jump from higher energy levels back down to lower energy levels.

Binary compounds

Substances made up of only two kinds of atoms, such as $H_2O$, $NH_3$, and $CO_2$.

Diatomic molecules

Elements that form two-atom molecules in their natural form at STP: $Br_2, I_2, N_2, Cl_2, H_2, O_2, F_2$ (BrINClHOF).

Pacific Atlantic Rule

A rule for counting significant figures: start from the Pacific (left) if a decimal is present, or the Atlantic (right) if it is absent.

Homogeneous mixtures

Mixtures that are uniform throughout, with solutions like air or salt water being the best examples.

Heterogeneous mixtures

Mixtures with discernable components that are not uniform throughout, such as soil or vegetable soup.

Solute

The substance being dissolved in a solution.

Solvent

The substance that dissolves the solute in a solution.

Electron configuration

The distribution of electrons in an atom, found at the bottom center of an element’s box on the periodic table.

Polyatomic ions

Groups of atoms with an overall charge, listed in Table E, such as $NO_3^{1-}$ or $SO_4^{2-}$.

Coefficients

Numbers written in front of formulas in chemical equations to give the ratios of reactants and products.

Physical changes

Changes that do not form new substances and merely change the appearance of the original material, like melting ice.

Chemical changes

Changes that result in the formation of new substances, such as burning hydrogen gas.

Endothermic reactions

Reactions that absorb heat, where the energy value is on the left side of the reaction arrow.

Exothermic reactions

Reactions that release energy, where energy is listed as a product in the reaction.

Synthesis reactions

Reactions occurring when two or more reactants combine to form a single product.

Decomposition reactions

Reactions occurring when a single reactant forms two or more products.

Law of Conservation of Mass

The principle stating that the mass of reactants is always equal to the mass of products in a chemical equation.

Gram formula mass

The sum of the atomic masses of all atoms in a substance, measured in $g/mole$.

Avogadro’s number

$6.02 \times 10^{23}$, representing the number of particles in $1 mole$ of a substance.

Sublimation

The phase change where a substance turns from a solid directly into a gas, characteristic of $CO_2$ and $I_2$.

Specific heat capacity formula

$q = mc\text{Δ}t$, used to calculate heat absorbed or released by substances.

Heat of fusion

The heat absorbed/released when $1 gram$ of a substance changes between the solid and liquid phases, which is $334 J/g$ for water.

Heat of vaporization

The heat absorbed/released when $1 gram$ of a substance changes between the liquid and gaseous phases, which is $2260 J/g$ for water.

Combined gas law

The formula $\frac{P_1V_1}{T_1} = \frac{P_2V_2}{T_2}$, where temperature must always be in Kelvins.

Distillation

A method to separate mixtures with different boiling points.

Filtration

A method to separate mixtures of solids and liquids.

Periodic Law

The law stating that the properties of elements are periodic functions of their atomic numbers.

Noble gases

Group 18 elements that are inert and stable because their valence-level electrons are completely filled.

Electronegativity

A measure of an element’s attraction for electrons, which increases as you move up and to the right on the Periodic Table.

Covalent bonds

Bonds formed when two atoms share a pair of electrons.

Ionic bonds

Bonds formed when one atom transfers an electron to another, typically with an electronegativity difference greater than $1.7$.

Molarity

A measurement of solution concentration equal to the number of moles of solute divided by the liters of solution.

Catalysts

Substances that speed up reactions by lowering their activation energies and can be reused many times over.

Entropy ($S$)

A property that is high in unorganized systems, such as a gas.

Oxidation

The loss of electrons by an atom or ion, resulting in an increase in the oxidation number.

Periodic law

properties of elements are functions of their atomic number

Periods

horizontal row

Groups

Vertical row

Luster

shine, reflects light

Conductivity

transfers heat and electricity

Malleability

ability to be shaped into sheets

Ductility

ability to be shaped into wire

What are the properties of metals?

Solid at room temp

Malleable

Ductile

Have luster

Good conductor

Lose electrons

Form positive ions with smaller radii

Low ionization energy and electronegativity

Transition Metals

Groups 3-11

D orbitals are full

Hard Solids High melting points

Form ions that have color 

Less active than groups 1-2

What are metalloids?

Found on the stair case

Have both metal and non metal properties

Nonmetals

not malleable or ductile

brittle in solid phase

lack-luster/ dull

Poor conductors

High ionization energy and electronegativity

gain electrons

Form negative ions with larger ions

Noble gases

Group 18

unreactive

Stable out electron configuration 

Allotrope**

elements that exist in different form; different structures and properties 

Atomic radius

the distance from the nucleus to the other energy levels

Metallic character

how much an element behaves like a metal

First ionization energy

the amount of energy needed remove the outermost, most loosely held electron from an atom

Electronegativity

a measure of an atom's ability to attract shared electrons to itself

Nuclear Shielding

the outermost electrons in an atom are isolated from the nucleus by the inner electrons

***The atomic radius..

Decreases across the period because of increases in nuclear charge

Increases down a group because of nuclear shielding

***The first ionization energy…

Increases across a period because of increases nuclear charge

Decreases down a group because of increased nuclear shielding

***Electronegativity is…

Increases across a period because of increased nuclear charge

Decreases down a group because of increased nuclear shielding

(same an IONIZATION energy)

Lewis Dot Diagrams

A diagram using the chemical symbol and valence elctrons of each element

All elements in the same group…

have the same number of valence electrons and have similar chemical properties

What did the foil gold foil experiment discover?

1.Most of an atom is empty space

2.Mass is concentrated in a dense nucleus

3.Electrons revolve in orbits around the nucleus

What is the atomic number?

The number of protons

How do you find the atomic mass?

protons + neutrons

What are electrons equal to?

the number of protons IF the atom is neutral/has no charge

What is the formula to find the charge?

protons + electrons = charge

What is an excited state?

an excited state occurs when an atom absorbs engery and one or more electrons move to a higher energy level

What is a continuous spectrum? 

Shows an unbroken sequence of frequencies

Line emission spectrum

has only certain frequencies of light as it is produced by excited atoms and ions as they fall back into a lower spectrum

Photons

A stream of tiny “energy packets”

Excited state

higher energy level reached by adding energy to an atom

Ground state

normal energy level electrons exist in

Emission

Electrons release energy in the form of visible light when they fall back to the ground state

How many electrons can a p orbital hold MAX?

6 electrons

How many electrons can a s orbital hold MAX?

2 electrons

How many electrons can a d orbital hold MAX?

10 electrons

How many electrons can a f orbital hold MAX?

14 electrons