Module 2 Notes

What makes an investigation credible and reliable?

if it is based on empirical evidence, peer-reviewed globally to reduce bias, and continuously reviewed using the scientific method.

Dalton’s Atomic Theory - Statement 1

All matter is composed of small, indivisible particles called atoms.

Dalton’s Atomic Theory - Statement 2

All atoms of a given element are identical in mass and properties.

Dalton’s Atomic Theory - Statement 3

Atoms cannot be subdivided, created or destroyed in chemical reactions.

Dalton’s Atomic Theory - Statement 4

Compounds are formed by a combination of two or more atoms in definite arrangements in the ratio of small whole numbers.

Dalton’s Atomic Theory - Statement 5

In chemical reactions, atoms are combined, separated, or rearranged.

What did Crookes Experiment involve?

experiments with cathode ray tubes, noting that a shadow appeared on the positive electrode, leading to the conclusion that particles were traveling from negative to positive.

How did Thomson’s work expand upon Crookes?

more detailed understanding of cathode rays and calculated the charge ratio for negatively charged particles, naming them electrons and developing the plum pudding model.

What was Rutherford's experiment?

fired alpha particles at gold foil, expecting them to pass through, but instead observed deflections indicating that the atom is mostly empty space and contains a dense nucleus with protons.

What did Chadwick discover in Chemistry?

identified the neutron, a subatomic particle with approximately the same mass as a proton but no charge, substantiating Rutherford’s hypothesis.

What is the current model of the atom?

consists of a dense nucleus containing protons and neutrons, with electrons in 3-dimensional orbitals surrounding it.

How can particles become ions?

when they gain or lose electrons; losing electrons makes them more positive, while gaining electrons makes them negative.

What are groups on the periodic table?

vertical columns on the periodic table, also known as families, with elements in the same group displaying similar properties.

Where are metals located on the periodic table?

found in groups 1-12 on the left side of the periodic table.

What are the physical properties of metals?

shiny, malleable, ductile, and good conductors of heat and electricity.

What are the physical properties of nonmetals?

dull, brittle, and poor conductors of heat and electricity, located on the right side of the periodic table.

What do we know about an atom if we know the atomic number?

indicates the identity of the atom and the number of protons.

What does the atomic mass tell us?

indicates the total number of protons and neutrons in an atom's nucleus.

How many protons, neutrons, and electrons are in Carbon-12?

has 6 protons, 6 electrons, and 6 neutrons.

What is required for an atom to be electrically neutral?

when the number of protons equals the number of electrons.

What is the quantum model of the atom?

introduces orbitals as complex, 3-dimensional shapes representing locations where electrons are likely to be found.

Where are negatively charged subatomic particles found?

are always found outside the nucleus of an atom.

What is the electron configuration of Argon?

1s2 2s2 2p6 3s2 3p6.

How are photons defined?

is a quantum of energy, representing a specific packet of energy.

How are energy, wavelength, and frequency related?

are directly related; as one increases, so does the other, while wavelength is inversely related to both.

What happens when an atom is placed in a flame?

Valence electrons gain energy, causing them to jump to higher energy levels, leading to the emission of light when they return to lower levels.

What is meant by ground state electrons?

are in their lowest energy levels and natural state.

What is an excited state electron?

is one that has absorbed energy and moved to a higher energy level.

What happens during an electron transition from n=3 to n=4?

absorbs a photon of energy to transition

What is Hund’s Rule?

every orbital in a subshell is singly occupied with one electron before any orbital is doubly occupied.

Is the configuration 1s2 2s3 2p6 reasonable?

the 2s sublevel can only hold a maximum of 2 electrons.

What does the principal quantum number represent?

indicates the energy level of electrons and ranges from 1 to 7.

What happens to an ion compared to its atom upon losing electrons?

the corresponding ion is smaller than the original atom.

Where do the most reactive metals occur on the periodic table?

located in the bottom left corner of the periodic table.

What is the trend for electronegativity across a period?

increases from left to right across a period due to increasing effective nuclear charge.

What is the trend for electron affinity across a period?

values become more negative as you go from left to right across a period.

How do electron radii of Ca and Ca2+ compare?

Ca2+ is smaller than Ca because it loses its outermost two electrons.

How do electronegativity and atomic radius relate?

Electronegativity increases as atomic radius decreases across a period.

What happens to ionic radius when gaining electrons?

makes the ion larger than its respective atom.

Which elements typically have the highest electronegativity?

Halogens, particularly fluorine

What happens to ionic radius when gaining electrons?

increases the ion's size compared to the atom.

What are isotopes?

are atoms of the same element that have the same number of protons but different numbers of neutrons.

What is a chemical bond?

is a lasting attraction between atoms that enables the formation of chemical compounds.

What is the difference between ionic and covalent bonds?

Ionic bonds involve the transfer of electrons from one atom to another, while covalent bonds involve the sharing of electrons between atoms.

What is an alkali metal?

are highly reactive metals found in group 1 of the periodic table, with one electron in their outermost shell.

What is a transition metal?

are elements found in groups 3-12 of the periodic table, known for their ability to form variable oxidation states and colored compounds.

What is a covalent compound?

is formed when two or more nonmetals share electrons to achieve stability.

What are noble gases?

are elements in group 18 of the periodic table that are inert and rarely react with other elements due to having full valence shells.

What does the octet rule state?

states that atoms tend to gain, lose, or share electrons to have eight electrons in their valence shell, achieving stability.

What is a supersaturated solution?

is a solution that contains more solute than it can normally hold at a given temperature.

What are the types of mixtures?

homogeneous (uniform composition) and heterogeneous (non-uniform composition).