Learn: Chemistry Study Guide Extensions

What is a pure substance?

Matter with a fixed, uniform composition; it is either an element or a compound.

What is an element?

A pure substance made of only one type of atom.

What is a compound?

A pure substance containing at least two different elements chemically combined in a fixed ratio.

What is a mixture?

Two or more substances physically combined; its composition can vary.

Is N₂ a pure substance?

Yes. It is a pure substance and an element because it contains only nitrogen.

Is C₆H₁₂O₆ a pure substance?

Yes. It is a pure substance and a compound because it contains multiple different elements in a fixed formula.

Is tea with sugar a pure substance?

No. It is a mixture.

Is brass a pure substance?

No. Brass is an alloy, so it is a mixture.

Is helium a pure substance?

Yes. Helium is an element.

What makes something a compound rather than a molecule of an element?

A compound contains at least two different elements; a molecule of an element contains atoms of only one element.

What is the atomic number?

The number of protons in an atom.

What is the mass number?

The total number of protons plus neutrons.

How do you calculate neutrons?

Mass number − atomic number.

How many protons are in ⁴⁸₂₂Ti²⁺?

22.

How many neutrons are in ⁴⁸₂₂Ti²⁺?

26.

How many electrons are in ⁴⁸₂₂Ti²⁺?

20.

What does the principal quantum number n describe?

The main energy level/shell.

What does ℓ describe?

The subshell type.

What are the ℓ values for s, p, d, and f?

s = 0, p = 1, d = 2, f = 3.

At what n does the s subshell first appear?

n = 1.

At what n does the d subshell first appear?

n = 3.

Which subshell corresponds to ℓ = 2?

d.

How many orbitals are in an s subshell?

1.

How many orbitals are in a p subshell?

3.

How many orbitals are in a d subshell?

5.

How many orbitals are in an f subshell?

7.

How many electrons can fit in one orbital?

2 electrons.

What is the formula for total orbitals in shell n?

n².

How many total orbitals exist when n = 3?

9.

What values can mℓ have?

All integer values from −ℓ through 0 to +ℓ.

What are the mℓ values for a d subshell?

−2, −1, 0, +1, +2.

How many electrons can occupy one mℓ = −2 orbital?

2 electrons.

How many electrons in a krypton atom have mℓ = −2?

2.

What is the charge of potassium ion K?

+1, written K⁺.

What is the charge of oxide ion?

−2, written O²⁻.

What is the formula of the ionic compound made from potassium and oxygen?

K₂O.

Why is potassium oxide K₂O?

Two K⁺ ions (+2 total) balance one O²⁻ ion (−2), giving a neutral compound.

What must the total charge of an ionic compound formula equal?

Zero (the compound must be electrically neutral).

Quick memory trick for subshells

s = 0, p = 1, d = 2, f = 3.

Quick memory trick for orbital counts

s/p/d/f = 1/3/5/7 orbitals.

How do you calculate electrons in a negative ion?

Protons + charge magnitude.

What is the formula for the number of orbitals in a subshell?

2ℓ + 1.

What values of ℓ correspond to an f subshell?

ℓ = 3.

What is the maximum number of electrons in a p subshell?

6 electrons.

How are the components of a mixture combined?

Physically combined with a variable composition.