Untitled Quiz

Atoms consist of protons, neutrons, and electrons.
Atomic mass (AR) is calculated as the sum of protons and neutrons.
Alpha decay involves the emission of an alpha particle, changing the mass and atomic number of the atom.
- Example: 238U → 4He + 234Th 92 2 90

Factual: This section focuses on how electron energy levels influence atomic reactivity and different ways to represent electron arrangements.
Conceptual: The organization of electrons in shells determines the oxidation states of atoms.
Debatable: The ability to control oxidation-reduction reactions of metals is a measure of human advancement.

Physicists have developed several models of atoms, making significant progress.
Thomson's plum pudding model depicted atoms as a positive sphere with negatively charged electrons embedded.
Rutherford's model showed a dense, positively charged central nucleus with electrons orbiting it.
Bohr proposed quantized orbits for electrons, where they can only absorb or release specific energy amounts to jump between them.
Schrodinger's wave equation is the most accurate atomic model, describing electrons as wave-particle duality within orbitals.

Electrons can be excited by absorbing specific amounts of energy and move to higher energy levels.
When excited electrons move back to a lower energy level, they emit energy in the form of light.
Different elements absorb and emit different energy levels of light, thus giving them distinct colours (visible spectroscopy).

Different colours correspond to specific wavelength intervals.
Students should create a table with compound names, chemical formulas, and observations from experiments like flame tests to correlate colours to energies. (A sample table is provided in the notes).

The colours in a flame test are due to the elements within the compound, not a physical change.
These colours are a result of electrons absorbing energy, becoming excited, and releasing it back out once they have returned to their ground state.
The table of wavelengths and colours can be used to identify substances.
Flame tests can be used in chemical analysis. Flame tests are helpful for observing the changes in colours emitted and correlating those colours to wavelengths

Wavelength and frequency are inversely proportional (c = fλ).
The speed of light constant (c) = 3.0 x 10⁸ m/s
Frequency (f) is related to energy (E = h x f) where h is Planck's constant = 6.63 x 10^-34 J·s

Work through practice problems on page 164: problems 1, 3, 4, 6, 7, 9, 11, and 14.

Atomic size increases down a group due to increasing electron shells.
Atomic size decreases across a period due to increasing nuclear charge and not increasing electron shells.
Core electrons cause shielding in the atom. Core electrons reduce the effect of the nuclear positive charge on valence electrons thus increasing atomic radius.

Electrons fill the orbits closest to the nucleus first.
Circular disks represent energy levels.
The first energy level holds 2 electrons, and the second level holds 8 electrons.

The outermost shell is called the valence shell.
Valence electrons are involved in chemical bonding.
Atoms can have multiple electrons in their outermost shell and not always be at the octet.
Noble gas atoms are stable and have a full valence shell, which gives them low reactivity.
The maximum number of electrons in a given shell is represented by 2n². Where n = the shell number.

Across a period the nuclear charge increases causing stronger pull on the valence electrons.
This pull causes contraction and a decrease in atomic radius.

First ionisation energy (IE₁) decreases down a group due to increasing shielding and atomic size.
First ionisation energy (IE₁) increases across a period due to increasing nuclear charge.
Electrons are held more closely to the nucleus in smaller atoms thus higher ionization energy.

Electronegativity (χ) is related to the ability of an atom to attract electrons involved in a chemical bond thus helps predict bond type (ionic or covalent).
Metals have lower electronegativities (left of the table).
High electronegativity occurs for nonmetals on the right side of the table.

Used to determine bond character (ionic or covalent) based on differences in electronegativity values (χ). The scale ranges between 0.8 to 4.0.
The larger the difference in electronegativity, the more ionic the bond.
Ionic bonds form when the difference in electronegativity is greater than 1.8.

Elements within the same group have the same number of valence electrons.
Some elements lose electrons (oxidation) to become positive ions (cations), others gain electrons (reduction) to become negative ions (anions)

Valency refers to combining capacity, while oxidation number refers to the charge.
Transition metals commonly have variable valencies.
Electron arrangement notation often only applies accurately to the first 20 elements. After which the concept loses its accuracy.
Calculating electrons in a shell: 2n² (where n = the energy level).

Dot and cross diagrams show electron arrangement during chemical bonding.
The diagram shows electron loss/gain during chemical reactions and resulting compound formation. Oxidation is loss; reduction is gain. This is a useful way to visualize the changes in valence shells during reactions and how these affect the outcome of the reactions.

Double bonds are represented by four dots that are very close together.
Multiple bonds involve the sharing of two or more pairs of electrons between atoms.

Lewis structures help represent octet rule by following a systematic approach for electron arrangements of compounds around an atom.
Atoms in the same group have the same number of valence electrons (e.g., F, Cl, Br, I have 7 valence electrons).