Chemistry Unit 1

Memory sheet

In cover mode, say each answer out loud before you tap. Testing yourself beats rereading — every time.

The 8 hooks

+ − 0

The three particles

Protons Positive · Electrons nEgative · Neutrons Neutral

Z A n

The three numbers

Z is protons · A is p + n · n = A − Z

ᴬZ

Nuclear notation

Big number on top, small number at the bottom

2882

Bohr filling

2 · 8 · 8 · 2 — fill from the inside out

C·V

Core & valence

Core = inside · Valence = the outermost occupied level

Isotopes

Same P, different N — same element, different mass

amu

Average atomic mass

Predict → Calculate → Check (+ amu)

Evaluate a claim

Verdict · Protons · Neutrons · Mass numbers · Odd one out

Evaluate a claim

The student's claim is incorrect.

__ and __ are the same element because they both have __ protons. The number of protons determines the identity of an element.

They are isotopes because they have the same number of protons but different numbers of neutrons (__ and __).

Their mass numbers are __ + __ = __ and __ + __ = __.

__ is a different element because it has __ protons.

Error analysis (Bohr)

The student's model is incorrect. The correct arrangement is __.

Electrons fill the lowest available energy level first: level 2 holds 8 before level 3.

Although the total is __, having the correct total does not make the arrangement correct.

Average atomic mass

Prediction: closer to __ amu because __ is more abundant.

(__ × __/100) + (__ × __/100) = __ amu

Reasonable: between __ and __, closest to __ (the most abundant isotope has the greatest influence).

Composition

Protons = Z = __

Electrons = protons = __ (neutral atom)

Neutrons = A − Z = __ − __ = __