4/4 Test Review

Which subatomic particle determines an element's identity?

• Proton

• Neutron

• Electron

• Photon

Answer explanation

The identity of an element is determined by the number of protons in its nucleus. Each element has a unique number of protons, which defines its chemical properties and distinguishes it from other elements.

How is the modern periodic table arranged?

• By atomic number

• By atomic mass

• By electron configuration

• By chemical properties

Answer explanation

The modern periodic table is arranged by atomic number, which reflects the number of protons in an atom's nucleus. This arrangement allows elements to be organized by their properties and behaviors, making it a fundamental aspect of chemistry.

What happens to atomic radius across a period and down a group?

• Decreases across a period, increases down a group

• Increases across a period, decreases down a group

• Remains constant across a period, increases down a group

• Decreases across a period, remains constant down a group

Answer explanation

As you move across a period, the atomic radius decreases due to increased nuclear charge pulling electrons closer. Conversely, down a group, the atomic radius increases because additional electron shells are added, increasing size.

Write the electron configuration for oxygen.

Evaluate responses using AI:

OFF

Answer explanation

Oxygen has 8 electrons. The electron configuration is 1s² 2s² 2p⁴, indicating 2 electrons in the first shell and 6 in the second shell, filling the 2s and 2p subshells.

What is the difference between ionic, covalent, and metallic bonding?

Evaluate responses using AI:

OFF

Answer explanation

Ionic bonding involves the transfer of electrons between atoms, creating charged ions. Covalent bonding involves the sharing of electrons, while metallic bonding features a sea of delocalized electrons among metal atoms, allowing conductivity.

Name the compound CaCl₂.

• Calcium chloride

• Calcium dichloride

• Calcium chlorine

• Calcium chlorate

Answer explanation

The compound CaCl₂ is named calcium chloride. The name reflects the presence of one calcium ion (Ca²+) and two chloride ions (Cl⁻), making 'calcium chloride' the correct nomenclature.

How many particles are in one mole?

• 6.022 x 10^23

• 1.00 x 10^23

• 3.00 x 10^23

• 9.00 x 10^23

Answer explanation

One mole of a substance contains 6.022 x 10^23 representative particles, known as Avogadro's number. This value is fundamental in chemistry for converting between moles and particles.

Calculate the molar mass of H₂O.

Evaluate responses using AI:

OFF

Answer explanation

To calculate the molar mass of H₂O, add the molar mass of 2 hydrogen atoms (2 x 1.01 g/mol = 2.02 g/mol) and 1 oxygen atom (16.00 g/mol). Total = 2.02 + 16.00 = 18.02 g/mol.

Tags

NGSS.MS-PS1-1

Identify the reaction type for 2KClO₃ → 2KCl + 3O₂.

• Decomposition

• Synthesis

• Single replacement

• Double replacement

Answer explanation

The reaction 2KClO₃ → 2KCl + 3O₂ involves the breakdown of potassium chlorate into potassium chloride and oxygen. This is characteristic of a decomposition reaction, where a single compound breaks down into simpler products.

Count the total atoms in the formula Al₂(SO₄)₃.

Evaluate responses using AI:

OFF

Answer explanation

In Al₂(SO₄)₃, there are 2 Al, 3 S, and 12 O (from 3 SO₄). Total atoms = 2 + 3 + 12 = 17.

Tags

NGSS.MS-PS1-1