Chemistry Semester 1 Final

Accuracy

how close a measurement is to the true value of the quantity that was measured

Precision

a measure of how close a series of measurements are to one another

Percent Error

Accuracy ~ Tells us how close lab data is to an actual/known value

Range

the difference between the highest and lowest scores in a distribution

Significant Figures

All the digits that can be known precisely in a measurement, plus a last estimated digit

Limit of Precision

Range of possible values where the true value of the measurement lies

-where to round to

-smallest increment/10

Leading 0's

never significant

Sandiwched 0's

Always Significant

Trailing 0's

only significant if there is a decimal

SigFigs with a decimal

All zeros to the right of a non-zero digit are significant

SigFigs without a decimal

All zeros to the right of the non-zero digit are never significant

Sigfigs Addition/Subtraction

round to the least significant decimal place

SigFigs Multiplication/Divison

round to the value with the least # of sigfigs

Sigfigs with scientific notation

1. Move decimal so there is only one digit to the left of it

2. Digit term should include the correct # of SFs

3. Exponent is the # of places that the decimal jumps

Pure substances can be ________ separated.

Chemically

Mixtures can be ________ separated.

Physically

Pure substances are classified into

elements and compounds

Compounds

2 or more elements chemically combined

Elements

A molecule composed of one kind of atom; cannot be broken into simpler units by chemical reactions.

Mixtures are eiether

Heterogenous or homogenous

Heterogenous

non-uniform mixture

Homogenous

uniform composition

Definition of density

How much mass (matter) is packed into a certain amount of space (volume)

Density =

mass/volume

atomic number

number of protons

number of protons in an atom equals the:

number of electrons

Mass number =

protons + neutrons

Isotope

Atoms of the same element that have different numbers of neutrons

Average atomic mass

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

Atom with an added/subtracted proton

New element

Atom with an added or subtracted neutron

Isotope

Ion

A charged atom

Definition of an ion

An atom or group of atoms that has a positive or negative charge.

Anion

A negatively charged ion

Cation

A positively charged ion

Valenece electrons

number of electrons in outermost energy shell

Octet rule

States that atoms lose, gain or share electrons in order to acquire a full set of eight valence electrons

Energy levels

the possible energies that electrons in an atom can have

S orbital

2 electrons

P orbital

6 electrons

D orbital

10 electrons

F orbital

14 electrons

Abbreviation of electron configuration

[noble gas] + remaining

why do orbitals occur

electrons move in waves and have spin, orientations need to combine the spin pairs

Aufbau Principle

An electron occupies the lowest-energy orbital that can receive it

Hund's Rule

electrons occupy orbitals of the same energy in a way that makes the number of electrons with the same spin direction as large as possible

Pauli Exclusion Principle

An atomic orbital may describe at most two electrons, each with opposite spin direction

Coloumbic Attraction

The force of attraction between positive and negative charges

An increase in # of protons causes what to increase?

Force of attaction

A decrease in the distance between what causes the FoA to increase?

Outer most e- and p+

AN increase in what does not divide the FoA?

electrons

Force of Attraction periodic table

Atomic Radius

Distance between the center of the nucleus and valence electron

Atomic radius periodic trend

Ionization energy

The amount of energy required to remove an electron from an atom

Ionization energy trend

Electronegativity

A measure of the ability of an atom in a chemical compound to attract electrons

electronegativity trend

Lewis dot diagrams

diagrams that show the bonding between atoms of a molecule and the lone pairs of electrons that may exist in the molecule.

Ionic compounds form when

oppositely charged ions attract

Formulas for ionic compounds

Write the cation element symbol followed by the anion element symbol.

The number of cations and anions must be correct for their charges to sum to zero.

Properties of ionic compounds

1. Conduct electricity

2. High melting points

3. Solids at room temperature

How are covalent compounds formed

by sharing electrons

Covalent formulas

Prefixes to subscripts tell how many atoms. Ex: N3P2=Trinitrogen diphosphide

properties of covalent compounds

1. DO not conduct electricity

2. Low melting points

3. Solids, liquids, or gases at room temperature

Monatomic Ions

ions formed from a single atom

Polyatomic ions

ions that are made of more than one atom

Naming ionic compounds

The name of the metal comes first, followed by the name of the nonmetal, changing the nonmetal's ending to "ide".

Cations

metals

Anions

nonmetals

When do you use Roman numerals?

transition metals

When do you use parentheses for polyatomic ions?

When a polyatomic ion is used more than once

How do you name covalent molecules?

1. Name first nonmetal

2. Name 2nd nonmetal (ide)

When do you use prefixes?

During covalent compounds

When does polarity occur?

when two atoms have a relative difference in electronegativities and share electrons unequally in a covalent bond

What does polarity create?

A dipole with slight + and - ends within a bond/molecule

What direction does a dipole arrow always point?

Toward the more electronegative atom

Change in Electronegativity <0.5

Non polar covalent

Change in Electronegativity 0.5-2

Polar covalent

Change in electronegativity >2

Ionic

What are inter molecular forces?

forces of attraction between molecules

If the IMFs are high, what is the phase of a substance

Solid

If the IMFs are medium, what is the phase of a substance

Liquid

If the IMFs are low, what is the phase of a substance

Gas

London Dispersion Forces

- occurs in all atoms/molecules

- electrons move to one side

- temporary/instantaneous divide

How to tell what has greater LDFS?

Number of electrons

Dipole Dipole

polar molecules

How to tell strength of dipole dipole?

Electronegativity

Hydrogen Bonding

Occurs in polar molecules with FON bonds

How to tell strength of HBs?

Number of FON bonds

Phase energy

The amount of energy needed to change the phase of a substance

Formula for phase energy

q=mH

Heat of fusion

Amount of energy required to change a substance from the solid phase to the liquid phase.

Heat of vaporization

The amount of energy required for the liquid at its boiling point to become a gas

Thermal energy

The amount of energy stored in moving particles

Formula for thermal energy

q=mcat

Specific heat energy

the amount of heat energy required to increase the temperature of one gram of a substance by one degree Celsius

Temperature

A measure of the average energy of motion of the particles of a substance.

Which direction does energy flow in?

hot to cold

Smaller specific heat means:

More mass needed for energy transfer