Chemistry Unit 1 Review

Atomic Number

The protons and electrons surrounding the nucleus of the element.

Average Atomic Mass (amu)

The average mass for a mole of atoms is measured in grams. Also referred to as Molar Mass

The horizontal row of the periodic table

periods

The vertical columns of the periodic table

groups

The mass number of an atom is the sum of it’s (blank)

Neutrons and Protons

Atoms of an element wtih different numbers of neutrons are called (blank)

Isotopes

Mass spectrometry technique

How the mass of various isotopes of an element can be determined.

The (blank) is the weighted average of all five isotope of selenium.

Average atomic mass

The (blank) serves as a bridge that connects all the different quantities.

Mole

Avogadro’s number describes the number of atoms that are in a single mole of any given element

Moles = 6.022 × 10²³

The relationship between Moles and Grams

Moles = (grams/molar mass)

The relationship between Moles and Gases

Moles = PV/RT (Pv=nrt)

22.4 L will always equal how many moles of gas?

22.4 L/mol

Molarity is the unit used for concentration, what is it’s relationship to moles?

Molarity (M) = moles of solute/liters of solution

How to find the Percent Composition

1. Seperate each element and count the number of atoms present

2. multiply the number of atoms by the atomic mass of each element

3. add the individual elements to get the molar of that compound.

4. Divide each mass by the total molar mass and multiply by 100% to get your percent composition

How to determine the empirical formula for a compound

1. When given % assume that it is a 100 gram sample, so you can turn it into grams

2. Once in grams, convert moles

3. divide each mole by the lowest value

How to determine the molecular formula for a compound

1. Determine the molar mass to the mass of the empirical formula

2. Ex: if the molar mass is twice the mass of the empirical formula, multiply by 2

The positively charged nucleus attracts the (blank)

negatively charged electrons surrounding it

The energy of electrons is quantized, which means (blank)

electrons can only exist only at specific energy levels, separated by specific intervals and you can’t have an in-between area

Coulomb’s Law

• electrons are more attracted to nuclei with more protons

• smaller force when they are farther apart

• Electrons closer to the nucleus are more attracted to it

• To remove an electron, electrostatic attraction must be overcome by adding energy. (ionization or binding energy.)

The Bohr Model predicts how the electrons orbit the nucleus at a fixed radii

• Each Energy level correspond with the rows on the periodic table

• The energy levels are n=1 to n=7

What happens when atoms absorb energy in the form of electromagnetic radiation?

Electrons jump to higher energy levels.

• When electrons drop from higher to lower energy levels, they give off energy in the form of electromagnetic radiation.

Different types of electromagnetic radiation

• Radio Waves

• Microwaves

• Visible Light

• UV light

• X Rays

Binding or ionization energy values for all electrons in an atom can be determined by (blank.)

Photo-electron spectroscopy

When a sample is hit with electromagnetic radiation, excess energy is converted to (blank.)

Kinetic energy

What types of electromagnetic radiations does it take to eject electrons from atoms?

• Visible

• Ultraviolet

• x-ray

What is the difference between Infrared radiation and microwave radiation?

• Infrared studies the vibrations of chemical bonds

• Microwave studies the shape and rotation

If the amount of ionization energy for all electrons ejected from a nucleus is charted you get (blank)

PES graph

The X and Y axis for the PES graph

• The Y axis describes the relative number of electrons that are ejected from an energy level

• The X axis shows the binding energy of those electrons and it decreases from left to right.

What do the peaks correspond to in PES graphs?

They correspond to the ejection of electrons in the same energy level.

Electrons in the same energy level can still have different binding energies, these represent (blank.)

subshells within each energy level, it describes the shape of the space the electron occupies

Each Subshell is divided into (blank.)

Orbitals and each orbital can hold two electrons

• Ex: p-subshell can hold 6 electrons in 3 different p-orbitals

Electron Configuration is a list of (blank)

shells, subshells and orbitals the electrons in an atom occupy

Aufbau Principle which states (blank)

Electrons are placed in shells, subshells and orbitals in order of increasing energy

The Pauli Exclusion Principle and Hund’s Rule

• Pauli exclusion Principle states that the two electrons that share an orbital cannot have the same spin

• Hund’s Rule says that when an electron is added to a subshell, it will always occupy an empty orbital if one is available

The electrons in the outermost s and p subshells are called

Valence electrons

Atoms that have gained or lost electrons are called

ions

Anions and Cations

• Anions are any ion with a negative charge

• Cations are positive ions

Periodic Trends

1. Electrons are attracted the protons in the nucleus of an atom

2. Valence electrons don’t experience the full charge of the nucleus. This is due to inner core electrons shield that repel them so they only experience effective nuclear charge

3. Completed shells are more stable

Valence Electron Periodic Trends

• Valence electrons to the right are more strongly attracted to the nucelus

• Atoms toward the top tend to be more strongly attracted to the nucleus

• Valence electrons on the top right corner are more strongly attracted to the nucleus

Atomic Radius Trends

• Moving left or down, the attractive force drops because of shielding or high energy levels being populated

• It decreases to the right and increases downward essentially

• Cations are smaller and Anions are larger than the corresponding atom

Ionization Energy

• increases to the right and decreases downward

• increased with the number of electrons removed

• Large spike means that electrons are removed from full subshells

Electronegativity

• Similar to ionization, it increases to the right and decreases downward

Electron Affinity

It is the change in energy when a gas-phase atom gains an electron but it also increases to the right and decreases downward on the periodic table