AP Chem Unit 1

What is the definition of a mole in chemistry?

The mole is a counting unit equal to 6.022×10²³ units, defined as the number of carbon atoms in exactly 12 grams of pure carbon-12.

How is molar mass defined?

Molar mass is the mass in grams of one mole of a compound, expressed in g/mol.

What is the equation to find the percent composition of an element in a compound?

The mass percent of an element = (mass of the element in 1 mole of compound / mass of 1 mole of compound) × 100%.

What does the term 'empirical formula' mean?

An empirical formula is the simplest ratio of atoms in a compound.

What is the purpose of Mass Spectroscopy?

Mass Spectroscopy identifies the chemical constitution of a substance by separating it into gaseous ions based on mass and charge.

What principle states that electrons occupy the lowest energy orbitals available?

The Aufbau Principle states that electrons occupy the lowest energy orbital that can receive them.

Describe Hund's Rule.

Hund's Rule states that when filling orbitals, each orbital in a subshell should be singly occupied before any orbital is doubly occupied.

What is the difference between atomic and molecular formulas?

An atomic formula gives the exact number and type of atoms in a molecule, while a molecular formula is the simplest ratio of the atoms in a compound.

What is Ionization Energy?

Ionization Energy is the energy required to remove an electron from a gaseous atom or ion.

How do atomic radii change across a period and down a group in the periodic table?

Atomic radius decreases from left to right across a period and increases down a group.

What is electronegativity?

Electronegativity is a measure of an atom's ability in a chemical compound to attract electrons.

What determines the effective nuclear charge (Zeff)?

Zeff is calculated as the number of protons minus the number of core electrons.

What trend is observed in ionization energy as you move down a group in the periodic table?

Ionization energy decreases as you go down a group because the valence electrons are farther away from the nucleus.

What is average atomic mass?

Average atomic mass is the weighted average of the masses of the naturally occurring isotopes of an element.

What is the formula for calculating the empirical formula from percent composition?

Convert percent to grams, then convert grams to moles, and divide by the smallest number of moles.

Explain the concept of electron affinity.

Electron affinity measures the energy change when an electron is added to a neutral gaseous atom to form a negative ion.