chem

Mixture

Two or more substances physically mixed together.

Homogeneous mixture (solution)

A mixture that looks the same throughout (uniform).

Ionic compound

A compound made of positive and negative ions attracted together.

Covalent compound

A compound where atoms share electrons.

Molecular substance

A substance made of molecules (usually covalent).

Anion

A negatively charged ion (gains electrons).

Cation

A positively charged ion (loses electrons).

Polyatomic ion

A bonded group of atoms with an overall charge (ex: OH⁻, SO₄²⁻).

Valence electrons

Electrons in the outer energy level of an atom.

Lewis structure

A drawing showing bonding and valence electrons (dots/lines).

Isotope

Same element, different number of neutrons.

Isotopic notation

A way to show an isotope using mass number and atomic symbol (and charge if ion).

Ionization

Removing electrons from an atom to form an ion.

Ionization energy

Energy needed to remove an electron from an atom.

Stable electron configuration

A full outer shell (often like noble gases).

Physical property

Observed without changing the substance (color, boiling point, etc.).

Chemical change

A change that forms new substance(s).

Physical change

A change in state or form; substance stays the same.

Accuracy

How close a measurement is to the true value.

Precision

How close repeated measurements are to each other (consistency).

Polarity

Unequal sharing of electrons in a bond.

Partial charge

Slight δ+ or δ− charges caused by polar bonds.

Frequency (ν)

Waves per second (Hz).

Wavelength (λ)

Distance between wave peaks.

Speed of light relationship

c = \lambda\nu

Photon energy

E = hf or E = hc/\lambda

Saline solution (salt water)

NaCl dissolved in water; a homogeneous mixture.

NaCl

Sodium chloride; an ionic compound.

Elements in saline solution

Na, Cl, H, O.

Chloride ion

Cl⁻ (the anion in NaCl).

Water bonding

Covalent bonds in H₂O (electron sharing).

Nitrogen gas

N₂ (two nitrogen atoms bonded).

Diatomic molecule

A molecule made of two atoms (ex: H₂, N₂, O₂).

Liquid nitrogen formation

Physical change (state change only).

N₂ Lewis structure

N≡N (triple bond), 10 valence electrons total.

Phosphorus trichloride

PCl₃; covalent compound.

Least electronegative in PCl₃

Phosphorus (P), so it goes in the center.

Chlorine group

Group 17 (halogens).

PCl₃ total valence electrons

26 (P:5 + 3 Cl:21).

Copper(II) sulfate

CuSO₄; ionic compound.

Sulfate ion

SO₄²⁻ (anion with 2− charge).

Lowest ionization energy in CuSO₄ context

Copper (Cu) (easiest to remove an electron from).

Average atomic mass (how to find)

Weighted average using isotope masses and abundances.

Hydrogen peroxide

H₂O₂; covalent compound.

H₂O₂ decomposition

H₂O₂ → H₂O + O₂ (chemical change).

H₂O₂ boiling point

~150.2°C (physical property).

Accuracy example (H₂O₂ lab)

Poor if average is far from 150.2°C.

Precision example (H₂O₂ lab)

Good/reasonable if measurements are close to each other.

H₂O₂ total valence electrons

14.

Aluminum hydroxide

Al(OH)₃; ionic compound.

Ions in Al(OH)₃

Al³⁺ and OH⁻.

Hydroxide ion

OH⁻ (polyatomic anion).

Most valence electrons (Al, O, H)

Oxygen (6 valence electrons).

Titanium(II) hydride

TiH₂.

Titanium cation

Ti²⁺.

Ti²⁺ electron configuration (given)

[Ar]3d².

Visible light in fireworks

Produced when electrons drop between energy levels.

Frequency ranking (low → high)

Red < Orange < Green.

Acetic acid

CH₃COOH; organic compound and weak acid (in vinegar).

Vinegar

Homogeneous mixture (solution) of acetic acid in water.

Bond polarity order (least → most)

C–H < C–C < C–O < O–H.

Most polar bond in acetic acid

O–H.

Partial charges in O–H bond

H is δ+ and O is δ−.

Organic compound

A compound containing carbon (often from living things).

Sucrose (table sugar)

C₁₂H₂₂O₁₁; organic compound.

Sugar caramelization

Chemical change around 186°C (new substance forms).

Ounces to grams

1 oz = 28.35 g.

7.00 oz in grams

198.45 g.

Sugar leftover calculation

198.45 g − 150 g = 48.45 g (≈48 g with sig figs).

Sulfur dioxide

SO₂; covalent compound (used to whiten sugar).

Most electronegative in SO₂

Oxygen (O).

O electron configuration (given)

1s² 2s² 2p⁴.

Sodium fluoride

NaF; ionic compound.

Ions in NaF

Na⁺ and F⁻.

Fluorine-22 (F⁻) protons

9.

Fluorine-22 (F⁻) neutrons

13 (22 − 9).

Fluorine-22 (F⁻) electrons

10 (9 + 1).

Non-combustible

Physical property.

Smallest element in sodium’s period (given)

Fluorine (F).

Aqueous NaF solution

Homogeneous mixture (solution).

Neon lighting

Gas tubes that emit colored light when electrified.

Gases mentioned (neon lighting)

Ne, H₂, He.

Most voltage needed (given)

Helium (hardest to ionize).

Least stable electron configuration (given)

Hydrogen (only 1 electron).

Hydrogen molecule Lewis structure

H–H (single bond), 2 valence electrons total.

Same group as fluorine

Chlorine (Cl).

Copper(II) phosphate

Cu₃(PO₄)₂; ionic compound and fertilizer.

Copper ion charge

Cu²⁺.

Phosphate ion charge

PO₄³⁻.

Charge balance in Cu₃(PO₄)₂

3 Cu²⁺ and 2 PO₄³⁻ balance to zero.

Metal vs nonmetal in Cu₃(PO₄)₂

Cu is a metal; P is a nonmetal.

Plant growth (as described)

Chemical change (new substances form).

Cu²⁺ electron configuration (given)

[Ar]3d⁹.

Which is larger (given)

Copper (Cu) larger than Phosphorus (P).